• LScanning tunneling microscopy and spectroscopy
• Low-dimensional quantum materials
• Topological insulators
• Unconventional superconductors
• High frequency measurements

Yonsei University, Seoul, Korea
Ph.D., Physics, Sep. 2005 – Aug. 2012

Yonsei University, Seoul, Korea
B.S., Physics, Mar. 1999 – Aug. 2005

Department of Physics, Yonsei University, Seoul, Korea
Assistant Professor, Sep. 2019 – NOW

Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
Postdoctoral research fellow, May. 2017 – Aug. 2019

Department of Physics and Astronomy, Rutgers University, New Jersey, U.S.A
Postdoctoral research fellow, Apr. 2016 – Apr. 2017

Institute for Basic Science (IBS), POSTECH, Pohang, Korea
Postdoctoral research fellow, Sep. 2013 – Mar. 2016

Department of Physics, Yonsei University, Seoul, Korea
Postdoctoral research fellow, Sep. 2012 – Aug. 2013

[14] Oh, C. G., Cho, D., Park, S. Y., and Rhim, J. W. ”Bulk-interface correspondence from quantum distance in flat band systems.” Communications Physics, 5, 320. (2022).

[13] Koen. M. Bastiaans, Damianos Chatzopoulos, Jian-Feng Ge, Doohee Cho, Willem O. Tromp, Jan M. van Ruitenbeek, Mark H. Fischer, Pieter J. de Visser, David J. Thoen, Eduard F.C. Driessen, Teunis M. Klapwijk, Milan P. Allan “Direct evidence for Cooper pairing without a spectral gap in a disordered superconductor above Tc” Science, 374, 608-611(2021).

[12] D. Chatzopoulos*, D. Cho*, K. M. Bastiaans*, G. O. Steffensen, D. Bouwmeester, A. Akbariand, G. Gu, J. Paaske, B. M. Andersen, and M. P. Allan. “Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe0.55Se0.45” Nature Communications 12, 298(2021).

[11] K. M. Bastiaans, D. Cho, D. Chatzopoulos, M. Leeuwenhoek, C. Koks, and M. P. Allan. “Imaging doubled shot noise in a Josephson scanning tunneling microscope” Physical Review B 100, 104506(2019).

[10] D. Cho*, K. M. Bastiaans*, D. Chatzopoulos, M. P. Allan. “A strongly inhomogeneous superfluid in an iron-based superconductor” Nature 571, 541-545 (2019).

[9] Maarten Leeuwenhoek, Richard A. Norte, Koen M. Bastiaans, Doohee Cho, Irene Battisti, Yaroslav M. Blanter, Simon Gr¨oblacher, and Milan P. Allan. “Nanofabricated tips for device-based scanning tunneling microscopy” Nanotechnology, 30, 335702, (2019).

[8] Sung-Hoon Lee, Jung Suk Goh, and D. Cho “Origin of the Insulating Phase and First-Order Metal-Insulator Transition in 1T-TaS2” Physcial Review Letters 122, 106404 (2019).

[7] K. M. Bastiaans*, D. Cho*, T. Benschop, I. Battisti, Y. Huang, M.S. Golden, Q. Dong, Y. Jin, J. Zaanen, M. P. Allan. “Charge trapping and super-Poissonian noise centres in a cuprate superconductor” Nature Physics 14, 1183-1187 (2018).

[6] K.M. Bastiaans, T. Benschop, D. Chatzopoulos, D. Cho, Q. Dong, Y. Jin, and M.P. Allan. “Amplifier for scanning tunneling microscopy at MHz frequencies” Review of Scientific Instruments 89, 093709 (2018).

[5] Doohee Cho, Gyeongcheol Gye, Jinwon Lee, Sung-Hoon Lee, Lihai Wang, Sang-Wook Cheong, and Han Woong Yeom. “Correlated electronic states at domain walls of a Mott-charge-density-wave insulator 1T -TaS2” Nature Communications 8, 392 (2017).

[4] Chul Lee, N. Leconte, Jiho Kim, Doohee Cho, In-Whan Lyo, E. J. Choi. “Optical spectroscopy study on the effect of hydrogen adsorption on graphene” Carbon 103, 109–114 (2016).

[3] Doohee Cho, Sangmo Cheon, Ki-Seok Kim, Sung-Hoon Lee, Yong-Heum Cho, Sang-Wook Cheong, and Han Woong Yeom. “Nanoscale manipulation of the Mott insulating state coupled to charge order in 1T-TaS2” Nature Communications 7, 10453 (2016).

[2] Doohee Cho, Yong-Heum Cho, Sang-Wook Cheong, Ki-Seok Kim, and Han Woong Yeom. “Interplay of electron-electron and electron-phonon interactions in the low temperature phase of 1T-TaS2” Phys. Rev. B 92, 085132 (2015).

[1] Woojin Jumg, Doohee Cho, Min-Kook Kim, Hyoung Joon Choi, and In-Whan Lyo. “Time-resolved energy transduction in a quantum capacitor” PNAS 108, 13973–13977 (2011).

* These authors equally contribute to this work

The Scanning Tunneling Microscope (STM) has become an essential tool for exploring the local electronic structure of correlated electron systems. However, its limited time resolution has prevented the acquisition of valuable information about the dynamics of electric charge transport. Shot noise, the temporal fluctuation of current due to the granularity of charges, is present in all STM measurements. Still, the relationship between shot noise and electronic properties remains poorly understood. In this work, we have combined a STM with a MHz amplifier that includes niobium inductors and a high-mobility electron transistor to achieve shot noise measurements at the atomic scale. This new technique has revealed unexpected charge dynamics in a cuprate high-temperature superconductor, a disordered superconducting TiN film, and vortex states in a putative topological superconductor FeSe0.45Te0.55. These findings provide new insights into understanding the electronic correlation properties hidden in time-averaged transport measurements of exotic quantum materials.

Stimulated emission depletion (STED) super-resolution microscopy (or nanoscopy) offers significant enhancement of optical resolution compared to conventional microscopy. To achieve resolution beyond the diffraction-limit, STED nanoscopy uses orders of magnitude (roughly ~10^5) more photons than the conventional confocal microscopy. Those additional ‘STED’ photons, which are designed to deplete the fluorescence at the periphery of focus, can induce unintended background noise. Increased low spatial frequency background noise decreases the signal-to-background ratio (SBR) and deteriorates the image quality by masking the high spatial frequency, super-resolved signal.
Here, we report simple and easy-to-implement methods to tackle the background noise problem in STED nanoscopy. Polarization switching STED (psSTED) efficiently suppress the low spatial frequency background appearing in STED images. In psSTED, we switch the STED beam polarization between two different circularly polarized states to record a regular STED image and a background noise image. A simple, unambiguous subtraction process between these two images accomplishes a background-free super-resolved image. Differential stimulated emission depletion (DiffSTED) method enhances contrast and resolution by reducing background noise and narrowing the point spread function. Finally, we compare the performance of the new methods with other state-of-the-art background subtraction methods and highlight their capability of efficient background suppression with a much simpler hardware implementation.

Prof. Meng Xiao received his BSc degree from Wuhan University in 2010 and his Ph.D. degree from the Hong Kong University of Science and Technology (HKUST) in 2014. After that, he worked as a postdoc fellow with Prof. C. T. Chan (at HKUST) and Prof. Shanhui Fan (at Stanford). He joined Wuhan University in 2018.

The role of nonlinearity on topology has been investigated extensively in Hermitian systems, while nonlinearity has only been used as a tuning knob in a PT-symmetric non-Hermitian system. Here, this talk shows that nonlinearity plays a crucial role in the topological classification of a non-Hermitian system. We provide a simple and intuitive example by demonstrating with both theory and circuit experiments an exceptional nexus (EX), a higher-order exceptional point with a hybrid topological invariant (HTI), within only two coupled resonators with the aid of nonlinear gain. The anisotropic critical behavior of the eigenspectra is verified with experiments. Our findings lead to advances in understanding the peculiar features of nonlinear non-Hermitian systems, possibly opening new avenues for applications.

Jungki Ryu is an Associate Professor at the Ulsan National Institute of Science and Technology (UNIST), South Korea. He received his B.S. and Ph.D. in Materials Science and Engineering from Yonsei University in 2006 and from the Korea Advanced Institute of Science and Technology (KAIST) in 2011. After postdoc research at the Massachusetts Institute of Technology, he joined the UNIST School of Energy and Chemical Engineering in 2014. His research interests include electrocatalysis for energy conversion, solar fuel production, biomass utilization, and electrochemical waste refinery.

Artificial photosynthesis is a promising technology for the efficient use of unlimited but intermittent solar energy. In principle, various chemicals can be produced in a sustainable manner through a series of photoelectrochemical reactions using water as a cheap and clean source of electrons. However, oxidation of water is a challenging task and acts as a bottleneck for the practical application of artificial photosynthesis technologies due to its slow kinetics and energy-intensive nature. In this presentation, we report novel photo(electro)catalytic systems for the efficient solar hydrogen production with simultaneous production of value-added chemicals via reforming of biomass. We found that certain catalytic electron mediators can depolymerize biomass to readily extract electrons and protons while selectively producing value-added chemicals via depolymerization. By utilizing electron mediators and biomass for anodic reactions for photo(electro)catalytic systems, we can produce hydrogen and valuable chemicals simultaneously under simulated sunlight irradiation. This approach allows efficient (photo)electrochemical production of hydrogen and brings additional economic benefits from byproducts.

2014 B.S. Osaka University
2016 M.S. Osaka University, Graduate School of Enginnering
2019 Ph.D. Osaka University, Graduate School of Enginnering
2016 JSPS Research Fellow
2019 Postdoctoral Fellow, Institute for Molecular Science
2020 JSPS Research Fellow, Institute for Molecular Science
2022 Research Assistant Professor, Institute for Molecular Science

Nano-optics, Optical Force

Nanospectroscopy of Optical Force
keywords : Optical force, Photoinduced force microscopy

Optical force is explained by the law of conservation of momentum between light and matter and has been utilized in applications such as optical trapping and laser cooling. Photoinduced force microscopy (PiFM) is a promising technology for detecting optical force and is a recently developed measurement technology based on atomic force microscopy. PiFM observes the interaction between light and matter through the motion of the probe tip. The physical origin of the measured quantity can be classified into two categories: one is the optical force exerted on the tip, and the other is photothermal expansion caused by the light absorption of the tip and sample. We have proposed a method called the heterodyne-FM technique to separate the effects of optical force and photothermal expansion, enabling us to measure pure optical force on a nanoscale [1]. Additionally, by conducting observations in ultrahigh vacuum, we have achieved nanospectroscopy of optical force with single-nanometer spatial resolution [2]. In this presentation, we will also present results from further applied measurements in photoinduced force microscopy.

[1] J. Yamanishi, et al., Phys. Rev. Applied, 9, 024031 (2018).
[2] J. Yamanishi, et al., Nat. Commn., 12, 3865 (2021).

Korea Advanced Institute of Science and Technology (KAIST) Daejeon, Korea
    B.S. Department of Materials Science and Engineering, February 2012.
    [Double major: Department of business management science]
Department of Materials Science and Engineering, KAIST
    Daejeon, Korea Graduate student, M.S. and Ph.D. integrated program
    Thesis advisor: Prof. Chan Beum Park (February 2012 – August 2018)

Advanced Biomaterials Lab, KAIST,Daejeon, Korea
    Postdoctoral Researcher, Supervisor: Prof. Chan Beum Park (September 2018 – July 2019)
Aging Research Lab, Korea Basic Science Institute (KBSI), Gwangju, Korea
    Visiting Researcher, Supervisor: Dr. Seongsoo Lee (January 2019 – July 2019)
UK Dementia Research Institute, University College London (UCL), London, UK
    Postdoctoral Researcher, Supervisor: Dr. Marc Aurel Busche (July 2019 – July 2022)
Amyloid Solution Inc., Seongnam-si, Korea
    Senior Research Scientist, Discovery 1Team, R&D group (Jan 2023 – present)

The accumulation of β-amyloid (Aβ) peptides in an abnormal manner is a representative feature of Alzheimer's disease, which is one of the most common types of age-related dementia worldwide. Despite a lack of clarity on the exact mechanism of neuronal loss and cognitive decline in AD, the idea that Aβ aggregation plays a crucial role in its pathology has received significant support from various in vitro and in vivo studies. In this respect, searching and developing therapeutic agents that can regulate Aβ aggregation is considered as an attractive option to treat AD. This talk will outline the attempts to employ light energy to intervene the self-assembly of Aβ peptides by generating oxidative stress by photosensitizers such as natural or synthetic dyes, light-responsive nanomaterials, and photoelectrochemical platforms. The mechanism behind photodynamic reactions reducing Aβ aggregation and the issue of creating oxidative stress, which has been long considered harmful, will be discussed, highlighting the positive impact of oxidative stress created by photosensitizers in suppressing Aβ-triggered neurotoxicity. Furthermore, the recent study to apply the photo-induced treatment in mouse model will also be presented.

2022.09-present
Assistant Professor, Department of Physics and Photon Science, Gwangju Institute of Science and Technology (GIST)

2019.04-2022.08
Postdoctoral Researcher, Max Planck Institute for the Structure and Dynamics of Matter
Humboldt Fellow (2020.9~2022.8)
NRF Next Academic Generation Fellowship (2019.9~2020.8)

2013.3-2019.2
Department of Physics, UNIST
Doctoral Thesis: Ab initio study of spin-phonon dynamics and band topology through the real-time time-dependent density functional theory
Advisor: Prof. Noejung Park
Nine bridge fellowship (2014.6~2017.5) Yebong Best Dissertation Award

2009.3-2013.2
School of Electrical & Computer Engineering, UNIST
Bachelor: Device Physics and Electrical Engineering

   Ab initio-based quantum mechanical calculation of dynamical states of matter; light- matter interaction such as ultrafast phase transition and attosecond electron dynamics.
   Non-equilibrium many-body simulation for quantum systems; light-enhanced superconductivity and cavity-matter interaction.
   Development of computational package and methods for density functional theory, time-dependent density functional theory, non-equilibrium green’s function and exact diagonalization.

1. Dongbin Shin, Simone Latini, Christian Schäfer, Shunsuke A. Sato, Edoardo Baldini, Umberto De Giovannini, Hannes Hübener, Angel Rubio, Simulating terahertz field- induced ferroelectricity in quantum paraelectric SrTiO3, Physical Review Letters 129, 167401 (2022).

2. Dongbin Shin, Nicolas Tancogne-Dejean, Jin Zhang, Mahmut Sait Okyay, Angel Rubio, Noejung Park, Identification of the Mott insulating CDW state in $1 \mathrm{~T}-\mathrm{TaS}_2$, Physical Review Letters, 126, 196406 (2021).

3. Dongbin Shin, Shunsuke A. Sato, Hannes Hübener, Umberto De Giovannini, Jeongwoo Kim, Noejung Park, Angel Rubio, Unraveling materials Berry curvature and Chern numbers from real-time evolution of Bloch states, Proceedings of National Academy of Sciences 116, 4135 (2019).

4. Dongbin Shin, Hannes Hübener, Umberto De Giovannini, Hosub Jin, Angel Rubio, Noejung Park, Phonon-derived spin-Floquet magneto-valleytronics in $\mathrm{MoS}_2$, Nature Communication 9, 638 (2018).

5. Javeed Mahmood†, Jungmin Park†, Dongbin Shin†, Hyun-Jung Choi, Jeong-Min Seo, Jung-Woo Yoo, Jong-Beom Beak, Organic Ferromagnetism: Trapping Spin in the Glassy State of an Organic Network Structure, Chem 4, 2357 (2018).

6. Dongbin Shin, S. Sinthika, Min Choi, Ranjit Thapa, and Noejung Park, Ab Initio Study of Thin Oxide–Metal Overlayers as an Inverse Catalytic System for Dioxygen Reduction and Enhanced CO Tolerance, ACS catalysis 4, 4074 (2014).

Light-induced phase transitions in condensed matter systems have attracted significant attention due to their potential applications and unprecedented physical phenomena. Recent studies have demonstrated light-induced topological phase transitions in materials such as $\mathrm{WTe}_2$ and $\mathrm{ZrTe}_5$ [1-2], which have been explained as a result of lattice dynamics caused by excited electronic structures [3]. Additionally, light-induced ferroelectric transitions are observed in quantum paraelectric $\mathrm{SrTiO}_3$ through mid-infrared and terahertz lights [4-5], with theoretical evidence suggesting the unique properties of the quantum paraelectric phase is the origin of this terahertz field-induced ferroelectricity [6]. This talk will provide an overview of recent studies on light-induced phase transitions in condensed matter systems including light- induced ferroelectricity in $\mathrm{SrTiO}_3$, light-induced topological phase transition in $\mathrm{HgTe}$, and cavity-induced topological phase transition in $\mathrm{WTe2}$, focusing on the microscopic mechanisms behind these transitions from an ab initio approach.

Hansuek Lee is Associate Professor in Department of Physics and Graduate School of Nanoscience and Technology at KAIST. He received his Ph.D. degree in electrical engineering from Seoul National University in 2008. From 2008 to 2015, he worked as postdoctoral scholar, research staff, and visiting associate at California Institute of Technology (Caltech), Pasadena, CA. His research focuses on various nonlinear and quantum phenomena from visible to mid-IR wavelength range boosted by ultra-high-Q resonators and low loss waveguides on a chip.

Chalcogenide glasses have attracted great attention due to their extraordinarily low material absorption in the mid-infrared wavelength range, in addition to their high nonlinearity and photorefractive effect. Here, we present a method for fabricating on-chip chalcogenide waveguides and resonators with extremely low optical loss. The loss was reduced to the level of the inherent material absorption by introducing a method for forming a light-guiding geometry on a chip by depositing a core material without a following etching process. The applications of these chalcogenide optical components are presented such as efficient supercontinuum generation and precise molecular sensing in the mid-infrared, which resolved the absorption spectra of the fundamental vibration state of carbon dioxide and carbon monoxide molecules.

(1) Educations
    - Ph.D. Electrical Engineering, California Institute of Technology, 2021.6
    - Thesis advisor: Professor Andrei Faraon
    - Thesis title: Dielectric metasurfaces for integrated imaging devices and active optical elements
    - B.S. Electrical and Computer Engineering, Seoul National University, 2016.8

(2) Employments
    - Research Scientist, Center for quantum information, Korea Institute of Science and Technology, South, 2022.9 ~ currrent
    - Postdoctoral Resarcher at Nanoscale and Quantum Photonics Lab at Stanford (with Prof. Jelena Vučković) (2021.7-2022.8)

(3) Research Interests
    - Nanophotonic devices for quantum information science, imaging, and sensing

Optical dielectric metasurfaces have shown great advances in the last two decades and become promising candidates for next-generation free-space optical elements. In addition to their compatibility with scalable semiconductor fabrication technology, metasurfaces have provided new and efficient ways to actively manipulate diverse characteristics of light. In this talk, we demonstrate nano-electromechanically tunable resonant dielectric metasurfaces as a general platform for novel reconfigurable free-space optical elements. First, we show different types of the phase and amplitude modulators. While one utilizes resonant guided-modes, the other is based on the high-Q asymmetric Mie resonances. Such devices achieve large phase modulation, small pixel-size, and electrical control of diffraction. Besides, we demonstrate tuning of circular-polarization dependent optical responses in dielectric chiral metasurfaces. Realizing wavelength-scale pixel size, low driving voltage, and large modulation simultaneously, these works pave the ways for the metasurfaces’ application to the next- generation spatial light modulators.

Dr. Haejun Chung is an assistant professor at Hanyang University since Sep 2022 working in the areas of inverse design of nanophotonic devices. He graduated with a magna cum laude B. S. degree in Electrical Engineering from Illinois Institute of Technology in 2010, then obtained M. S. (2013) and Ph. D. (2017) degrees both from Purdue University. He joined Applied Physics at Yale University as a Postdoctoral Research Associate, developing a fast inverse design algorithm and novel metasurfaces. In 2020, He joined MIT Mechanical Engineering as a Postdoctoral Research Associate for developing large-area metalenses, tunable metasurfaces.

Metasurfaces are patterned optical thin films that offer the possibility of manipulating light, for applications from holography to lenses, with precision equal to or greater than their bulky conventional optics counterparts. In this talk, we prove that the unit-cell approach, a conventional metasurface design method, cannot have high efficiency for rapidly varying phase and amplitude; conversely, we demonstrate that “inverse design,” a large-scale computational design technique optimizing all geometrical degrees of freedom can discover high-numerical-aperture (“fast”) lenses that operate over visible bandwidths with the highest efficiencies. In addition, I will introduce best-in-class photonic devices achieved by inverse design such as metalenses, phase singularity generation.

Incheon National University, Ph.D, Physics, 2022
Incheon National University, BS, Physics, 2016

· Best Poster Presentation Award (The 12th international conference on advanced materials and devices)
· Best Poster Presentation Award (Optical Society of Korea)
· Best Poster Presentation Award (The 19th international symposium on the physics of semiconductors and applications)

· Hyuntae Kim, Jaeseung Im, Kiin Nam, Gang Hee Han, Jin Young Park, Sungjae Yoo, MohammadNavid Haddadnezhad, Sungho Park, Woongkyu Park, Jae Sung Ahn, Doojae Park, Mun Seok Jeong and Soobong Choi, "Plasmon-exciton couplings in the MoS2/AuNP plasmonic hybrid structure." Scientific Reports 12.1 (2022): 22252.
· Heewoo Lee, Jin Young Jeong, Hyuntae Kim, Woongkyu Park and Soobong Choi, "High-throughput fabrication of TERS probes using DC bias." Current Applied Physics 32 (2021): 86-90.
· Woongkyu Park, Hyuntae Kim, Hajung Park, Soobong Choi, Sung Ju Hong and Young-Mi Bahk , “Biochar as a low-cost, eco-friendly, and electrically conductive material for terahertz applications." Scientific Reports 11.1 (2021): 18498.
· Hyuntae Kim, Woongkyu Park, Kiin Nam, Hyun Seok Jang, Byoung Hoon Kim, Soobong Choi, "Effects of electron beam irradiation on the friction and work function of the wrinkled graphene." Current Applied Physics 19.11 (2019): 1172-1176.
· Jun Woo Jeon, Hyeonbeom Kim, Hyuntae Kim, Soobong Choi and Byung Hoon Kim, "Experimental evidence for interlayer decoupling distance of twisted bilayer graphene." AIP Advances 8.7 (2018): 075228.
· Hyuntae Kim and Soobong Choi. "Growth of sheet-like ZnO nanostructures on ZnO nano rods using chemical bath deposition." Applied Science and Convergence Technology 27.2 (2018): 38-41.
· D. J. Park, T. H. Kang, D. S. Kim, H. T. Kim and S. B. Choi "A carbon contamination cleaning of gold film by electron beam irradiation with minimum structural damages." Journal of the Korean Physical Society 71 (2017): 467-470.
· Jun Woo Jeon, Se Youn Cho, Yu Jin Jeong, Dong Seok Shin, Na Rae Kim, Young Soo Yun, Hyun-Tae Kim, Soo Bong Choi, Won G. Hong, Hae Jin Kim, Hyoung-Joon Jin, Byung Hoon Kim, "Pyroprotein‐based electronic textiles with high stability." Advanced Materials 29.6 (2017): 1605479.

· Light-matter interaction in nanoscale
· Metrological Inspection in semiconductor manufacturing processing
· Hyper-spectroscopic image and analysis in nanoscale

Since the exciton modes in two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been experimentally and theoretically studied due to their interesting behaviors. The hybrid structure of noble metal nanoparticles (NPs) with TMDCs has been introduced to enhance the light-matter interaction caused by plasmon-exciton couplings. The techniques for enhancing the optical response are based on the local EM field confinements on a metallic nanostructure referred to as the localized surface plasmon resonance (LSPR).
In this presentation, I will introduce the tip-enhanced cavity spectroscopy (TECS) techniques for highly enhancing optical responses and suggest the intertwined mechanism of plasmon-exciton couplings in each exciton mode on the hybrid structure of the monolayer molybdenum disulfides ($\mathrm{MoS}_2$) and non-centrosymmetric AuNP. Here, I will also summarize the emission of strain-induced localized excitons ($\mathrm{X}_{\mathrm{L}}$) mode, which could not be observed at room temperature due to the low binding energy. Furthermore, the correlation between the optical responses and electrical characteristics is analyzed by Kelvin probe force microscopy (KPFM).

Infrared photoinduced force microscopy (IR-PiFM) provides unique vibrational information of samples with nanoscale resolution, which has been widely used in optics, polymer science and biosciences. However, the detection limit of IR-PiFM is limited by the weak light-matter interaction of ultrathin samples. Thus, for interfacial studies, promotion of sensitivity is highly desired. Here, we have summarized our recent processes of IR-PiFM performed on ultrathin sample with promoted sensitivity, including the experimental set-ups for solid/gas interface and solid/liquid interfaces analysis and the related applications.
Jian Li received his B.S. and Ph. D degrees in Chemistry from Nanjing University (China). He is currently an associate researcher at Nanjing University (China). His research focuses on photo induced force microscopy, plasmon enhanced infrared spectroscopy and plasmon enhanced chemistry.

Min Seok Jang is an associated professor of Electrical Engineering at KAIST. He received Ph.D. degree in Applied Physics from California Institute of Technology (Caltech) in 2013. His research interest includes polaritons in van der Waals crystals and their applications in active meta-optical devices. He is a Fellow of the Optical Society of Korea (OSK) and a member of the Young Korean Academy of Science and Technology (Y-KAST).

Polaritons in two-dimensional materials have been attracting enormous research interest due to their deep-subwavelength field-confinement enabling strong light matter interactions. In this presentation, I introduce a new class of polaritonic modes – image polaritons - that appear when a polaritonic material is in close proximity to a highly conductive metal, so that the polaritonic mode couples with its mirror image. The image polaritons constitute an appealing nanophotonic platform, providing an unparalleled degree of optical field compression into nanometric volumes while exhibiting lower normalized propagation loss compared to conventional van der Waals polaritons on nonmetallic substrates. I will cover three different mid-infrared image polaritons in van der Waals Crystals: image plasmons in graphene and image phonon polaritons in h-BN and α-MoO3.

Junghoon Jahng received his B.S in Physics from University of Seoul (ROK), M.S in Physics and Astronomy from Seoul National University (ROK) and Ph. D in Physics and Astronomy from University of California, Irvine (US). Currently, he works as a Principal Research Scientist at the Korea Research Institute of Standards and Science. His research focuses on nano-femto scale physics via force detection technique.

This work investigates the nonlinear optical force between a sharp tip and a sample that had been photo-excited by using the time-resolved pump-probe force microscopy. By measuring this force, we are able to study the nonlinear polarization of the material. Our findings reveal that the ground state bleaching of excitons in 2-D materials is influenced by the same excited state dynamics observed in optical pump-probe experiments. We have demonstrated that ultrafast pump-probe force microscopy is a non-optical detection technique that can achieve nano-femto scale resolution, thus enhancing the sensitivity of pump-probe experiments to the point where they may be used for single-molecule studies.

Ki Su Kim is an Associate Professor in the School of Chemical Engineering at PNU. He received his Ph.D. degree in 2012 from the Department of Materials Science and Engineering, POSTECH. In 2012, he moved to Harvard Medical School and worked as a research fellow in the Wellman Center for Photomedicine at Massachusetts General Hospital (2012-2015), and then as a postdoctoral research fellow in the Center for Nanomedicine, Brigham and Women’s Hospital (2016-2017). His Smart NanoBiomaterials Laboratory conducts cutting-edge research focusing on making breakthroughs in the development of nano-enabled smart biomaterials and technologies for various biomedical applications, such as photomedicine, drug delivery, tissue engineering, bioimaging, and medical devices

A variety of drug delivery systems have been investigated for high therapeutic efficacy via easy administration. Among them, transdermal delivery is presented as an attractive alternative to needle-based drug delivery because of patient preferences. Although transdermal microneedles are less invasive promising alternatives, needle‐free topical delivery without involving physical damage to the natural skin barrier is still sought after as it can further reduce needle‐induced anxiety and is simple to administer. However, this long-standing goal has been elusive since the intact skin is impermeable to most macromolecules. Here, we show an efficient, noninvasive transdermal delivery using Hyaluronic acid (HA) derivatives as carrier. In addition, we present the recent results of non-invasive transdermal photomedicine using various organic/inorganic upconverting nanomaterials with HA. As the upconversion nanoparticle (UCNP) can be served as small sized visible-light source, we successfully demonstrated the facilitated photomedicine application including photochemical tissue bonding and antibacterial therapy. These platform technologies might be successfully applied for the development of various futuristic nanomedicines.

- Ki Young Lee is a postdoctoral research fellow in the Department of Physics at Hanyang University in Seoul, Korea.
- He received his Ph.D. in Physics from Hanyang University in February 2022.
- He was selected as a Sejong Science Fellow by National Research Foundation of Korea and has been leading a research project on topological metasurfaces since 2022.

Photonic transport of In-plane topological states, achieved by emulating Hermitian electronic systems has received significant attention.
However, their out-of-plane radiation remains largely unexplored. By treating leakage radiation as non-Hermiticity, the extension of the topological notion to the resonant metasurfaces presents promising opportunities in terms of a new means for directly measuring topological bands and extra functionalities for free-space applications.In this talk, we investigate the fundamental mechanism of far-field radiation and resonant excitation in the topological junction metasurfaces consisting of thin film dielectric subwavelength gratings. These structures exhibit unique topological features such as complex-valued Dirac-mass, Berry phase, and band structures represented by Fano spectral responses. Considering the correlation between the topological quantities and structural parameters, we discuss new optical functionalities discovered in the topological metasurfaces, including topological beam shaping and anomalous transmissive pure-phase-resonances.

Myoung-Gyun Suh is a senior scientist at NTT Research, Inc. His primary research interest is in optical precision measurements and information processing systems. He has focused on developing innovative chip-based optical sources and exploring their applications to precision spectroscopy, astronomy, optical communication, and computation. Recently, he has been studying integrated nonlinear optics, optical frequency combs, and neuromorphic computing. Dr. Suh earned a B.S. in Physics from Korea Advanced Institute of Science and Technology in 2004, an M.S. in Physics from National Taiwan University in 2006, and a Ph.D. in Applied Physics from the California Institute of Technology in 2017. For his earlier research, Dr. Suh was fascinated by light-matter interaction phenomena in photonic crystal structures and studied two-dimensional photonic crystal lasers for his B.S. and M.S. degrees. After his M.S., Dr. Suh worked at Samsung Advanced Institute of Technology from 2006 to 2011, where he developed high-efficiency Gallium Nitride light-emitting diodes and III-V multi-junction solar cells. He has been the recipient of a Taiwan scholarship (2004-2006), Kwanjeong scholarship (2011-2015), and OSA Paul F. Forman team engineering excellence award (2020).

Optics plays a vital role in our modern information society. Optical communication enables a faster and more energy-efficient flow of information, and various optical measurement technologies aid in the acquisition of information from the environment. Among many optical technologies, optical frequency combs stand out as a potent optical technology, offering vast optical parallelism and unparalleled precision in time and frequency metrology. Recent advances in chip-integrable optical frequency combs, or microcombs, could make frequency combs more widely accessible. Additionally, there is growing interest in physical computing systems that utilize optical technology, and microcombs are a promising optical source for compact, energy-efficient, high-capacity optical computing systems with high clock frequency or massively-parallel optical channels. In this talk, I will discuss our research on soliton microcombs and their application in computation, specifically in solving combinatorial optimization problems.

Sangsik Kim is an associate professor in the School of Electrical Engineering at the Korea Advanced Institute of Science and Technology (KAIST). Before joining KAIST, he was an assistant professor in the Department of Electrical and Computer Engineering (ECE) at Texas Tech University. He was also a postdoctoral research associate at the National Institute of Standards and Technology (NIST) and in ECE at Purdue University, where he received an MS and a Ph.D. He received his BS in ECE from Seoul National University, South Korea. He is a recipient of the US NSF CAREER Award, the KSEA Young Investigator Award, and the Whitacre Engineering Research Award.

Wave propagation in lossy media is typically characterized by exponential intensity decay. However, recent research has linked exceptional point (EP) singularities in non-Hermitian systems to unconventional wave propagation. In this talk, we will present our recent discovery and demonstration on EPs-led exponential-decay-free wave propagation in a uniform lossy medium. A nanostructured photonic slab waveguide with EPs is used to observe up to 400-waves of deep wave propagation with a uniformly distributed energy loss. This unconventional wave propagation was analyzed by coupled-mode theory and electromagnetic simulations, confirming its relation to EPs. These results hold true across other physical waves and have immediate applications for generating large, uniform, and surface-normal free-space plane waves directly from photonic chips.

Dr. Sangwan Sim is an Assistant Professor at Hanyang University ERICA in Ansan, South Korea. He earned his PhD from Yonsei University in 2017 and went on to postdoctoral research at the Los Alamos National Laboratory in the United States. In 2019, he joined Hanyang University ERICA where he now focuses his expertise on ultrafast light-matter interactions in nano- and quantum materials.

The low-symmetrical 2D materials, such as black phosphorus, ReS2, GeSe, and SnSe, possess in-plane crystal anisotropy, opening up new avenues for developing advanced optical, electrical, and thermal devices. Their optical anisotropy provides a path for creating highly polarized light detectors, emitters, and optical information devices. In recent years, ultrafast tuning of the anisotropic optical characteristics in these materials has gained interest due to its potential for high-speed polarization-controlled optical devices. Furthermore, the unique quasi-1D dynamics of photocarriers with orientation-dependent mobilities and diffusivities displayed in ultrafast spatiotemporal dynamics is crucial information for advancing the anisotropic device technologies. We will discuss the anisotropic, transient optical modulation and carrier diffusion of low symmetrical 2D materials, including ReS2 and ZrTe5, studied using ultrafast pump-probe spectroscopy. Our focus will be on their strong polarization-dependent ultrafast photo-induced dynamics, offering ample opportunities for ultrafast modulation applications. The orientation-dependent ultrafast carrier diffusion observed by spatiotemporal scanning pump-probe microscopy will also be covered.

Sejeong Kim is a lecturer (= Assistant professor) at the University of Melbourne, Australia. She obtained her PhD in Physics from the Korea Advanced Institute of Science and Technology (KAIST) in 2014. She was a research fellow at the University of Technology Sydney (UTS). Her research focuses on developing light-matter interaction at the nanoscale, particularly using optical/plasmonic cavities. This includes studies of photonic crystal cavities for microlasers, sensors and quantum applications, as well as the development of an integrated photonics platform. She is one of the 30 Rising Stars selected by the Optical Society of Korea. She is currently Optica’s Nanophotonics Technical Group leader and 2023 Optica Ambassador.

Two-dimensional (2D) materials are extensively used in almost all scientific research areas, from fundamental research to applications. Initially, 2D materials were integrated with conventional non-2D materials having well-established manufacturing methods. Recently, the concept of constructing photonic devices exclusively from 2D materials has emerged. Various devices developed to date have been demonstrated based on monolithic or hetero 2D materials. In this presentation, photonic devices that solely consist of 2D materials will be discussed, including photonic waveguides, lenses, and optical cavities. Exploring photonic devices that are made entirely of 2D materials could open interesting prospects as they enable the thinnest devices possible because of their extraordinarily high refractive index. In addition, unique characteristics of 2D materials, such as high optical anisotropy and spin-orbit coupling, might provide intriguing applications.

Sung is the CEO of Molecular Vista, which he co-founded with Prof. Kumar Wickramasinghe (UC Irvine, formerly of IBM) in 2011 to provide research and industrial tools for rapid and nanoscale imaging with chemical identification. Sung has over 25 years of experience of industrial R&D, engineering, marketing and sales, and operations. He co-founded Park Scientific Instruments (PSI), which was one of the first commercial companies to develop and sell scanning tunneling microscopes (STM) and atomic force microscopes (AFM). Prior to founding Park Scientific Instruments, he worked as a post-doc at IBM Watson Research Center. Sung earned his Ph.D. in Applied Physics from Stanford University and BA in Physics from Pomona College.

While quantitative elemental mapping at nanoscale (~1 to 10 nm) has been available for many years via EDX in transmission electron microscopy, the best quantitative molecular mapping has been limited to a spatial resolution of ~200 nm for ToF-SIMS. With optical spectroscopy, even though tip-enhanced Raman spectroscopy (TERS) has demonstrated single-molecule sensitivity on an isolated molecule, mapping of 2D and 3D materials with nanoscale spatial resolution has proven to be difficult due to the large far-field contribution. In this talk, a non-destructive quantitative molecular spectroscopy/mapping technique called infrared photo-induced force microscopy (IR PiFM) is introduced. It combines IR spectroscopy with atomic force microscopy to provide both structural imaging and IR spectro-nanoscopy with sub-5 nm spatial resolution and single-molecule-level sensitivity. PiF-IR spectra on homogeneous samples agree with their bulk FTIR spectra extremely well even though PiF-IR’s sampling volume is at least billion times less. On samples with nanoscale heterogeneity, whether chemical or structural (such as crystallinity) in nature, PiF-IR spectra reflect the local chemical bonding environments. Examples from various organic, inorganic, and biological samples will be presented to showcase the capabilities of IR PiFM.

2011. 03 – 2017.02	B.S., Department of Physics, Pusan National University (PNU)
2017. 03 – 2023.02	Ph.D., in Department of Physics, Korea Advanced Institute of Science and Technology (KAIST)

2023 – present

Postdoctoral Researcher, Department of Physics, Korea Advanced Institute of Science and Technology (KAIST)

1. Probing the dynamics properties of novel semiconductors with ultrafast optical and THz spectroscopy
“Efficient perovskite solar cells via improved carrier management,” Nature 590, 587 (2021).
“Probing surface trap and recombination velocity in Bi2O2Se”, in preparation (2023).

2. Ultrafast interlayer charge transfer in metallic vdW heterostructures
“Interlayer Coupling and Ultrafast Hot Electron Transfer Dynamics in Metallic VSe2/Graphene van der Waals Heterostructures”, ACS Nano 15, 7756 (2021).
“Ultrafast interfacial carrier dynamics and persistent topological surface states of Bi2Se3 in heterojunctions with VSe2”, Commun. Phys. 5, 1-11 (2022).

3. Ultrafast control of nanomaterials and coherent phonon spectroscopy
“Coherent control of interlayer vibrations in Bi2Se3 van der Waals thin-films” Nanoscale 13, 19264-19273 (2021).
“Ultrafast formation of quantized interlayer vibrations in Bi2Se3 by photoinduced strain waves” Opt. Express 30, 35988-35998 (2022).
“Photoinduced topological phase transition by coherent interlayer vibrations” in preparation (2023).
“Interlayer vibration assisted all-optical acousto-optic modulation at optical communication wavelengths with hypersonic speed” in preparation (2023).

Ultrafast manipulation of material phases and properties through photoexcited electrons and lattice subsystems in quantum materials is attracting attention for novel optoelectronic applications in a high-speed and reversible manner [1,2]. In particular, topological insulators, which possess insulating bulk states and conducting Dirac surface states, are expected that topological phases are sensitive to uniaxial mechanical strain. However, previous efforts to induce significant changes in topological order using mechanical strain have been limited by the formation of in-plane cracks [3]. To overcome this limitation, an optical method is proposed: using photoinduced strain to selectively generate the out-of-plane strain, which can excite the unique interlayer vibrational modes in Bi2Se3 by confinement at the nanoscale. These interlayer vibrations modify the van der Waals distance and corresponding complex refractive index at a hypersonic speed based on the photoelastic interaction in bulk bands. Furthermore, the topological phase modulation can be achieved with sufficient photoinduced strain, leading to the bipolar and selective control of charge transport in topologically protected surface and bulk states. In this talk, experimental results will be discussed with DFT calculations. These observations provide fundamental insight into nanomechanical lattice-topological phase interactions for potential applications such as acousto-optic modulators and topological switching with time-varying protocols.

Vasily Kravtsov has graduated from M. V. Lomonosov Moscow State University (Russia) and received a PhD degree in Physics from University of Colorado at Boulder (USA) in 2017. He has worked as a research assistant at the Physics Department of CU Boulder and Joint Institute for Laboratory Astrophysics (JILA), focusing on experimental research in near-field optics, nanotechnology, and femtosecond laser pulses. In 2018 Vasily joined ITMO University (Saint Petersburg, Russia) as a leading research fellow. Currently, Vasily is an assistant professor and group leader at the School of Physics and Engineering, ITMO University. His research interests include two-dimensional quantum materials, ultrafast spectroscopy, and nonlinear nano-optics.

Atomically thin transition metal dichalcogenides (TMDs) are direct band gap semiconductors that host excitons with large binding energies and sizeable exciton-exciton interaction strength. When stacked into heterostructures, these materials acquire many unique optical properties associated with the interlayer coupling and formation of new excitonic and polaritonic states. Near-field spectroscopy provides an indispensable tool for studying such states, as well as their coupling, dynamics, and control. I will present results of our recent investigation of excitonic effects in van der Waals heterostructures via different near-field spectroscopy implementations including tip-enhanced spectroscopy and spectroscopy in the Fourier plane via evanescent wave coupling through a solid immersion lens. First, I will discuss the possibility of controlling the intralayer and interlayer excitons within a nanoscopic volume of TMD heterobilayers. Second, I will discuss experiments on probing and controlling exciton-polaritons in van der Waals heterostacks in the strong light-matter coupling regime.

Professor, University of science and technology of China. His research interests include quantum photonic integrated circuits, quantum nanophotonics, quantum optics, quantum information, etc. So far, he has published 117 SCI papers in these research fields, in which 48 were published in recent 5 years, including 1 in Science, 1 in Nature, 5 in Phys. Rev. Lett., 2 in Light-Sci. Appl., 2 in Optica, etc.

Integrated quantum photonics has attracted intensive attention due to the compactness, scalability, and stability. Quantum photonic source, especially an on-chip entangled photon source, is a basic device for realizing quantum photonic integrated circuits (QPICs). I will introduce our recent works about quantum photonic sources based on nanophotonic structures, such as 2D materials, metalens array, microcavity, nanowaveguide, etc.

Mark is a professor of photonics at Stellenbosch University in South Africa. His research is in the area of quantum nanophotonics, which involves the nanoscale control of light and its interaction with matter in the quantum regime. The goal of his research is to explore potential applications of nanophotonic devices for carrying out quantum computing, quantum communication and quantum sensing. His work is experimental and theoretical in nature.

Mark received his Ph.D degree from Queen’s University Belfast, United Kingdom, in 2007. After postdoctoral fellowships at Osaka University in Japan (with Prof. Nobuyki Imoto) and Imperial College London (with Prof. Myungshik Kim and Prof. Stefan Maier), in 2013 he joined the faculty at the University of KwaZulu-Natal in Durban, South Africa as an Associate Professor. In 2018, he moved to the Laser Research Institute at Stellenbosch University to take up a Research Chair.

Mark has published over 60 papers in internationally leading journals on various topics in quantum information and nanophotonics, including Nature Physics, Nature Photonics, Nature Communications and Physical Review Letters. He has also published 2 book chapters, 2 review articles and a number of conference proceedings. He currently leads a team of 2 postdocs, 3 PhD students and 1 MSc student. His group’s website is: www.quantumnanophotonics.org.

Integrated photonic systems provide an attractive platform for quantum state engineering. Dielectric materials are often used to construct complex optical circuitry in this setting, but plasmonic materials can provide a way to confine light to much smaller scales, which enables more compact devices and the enhancement of light-matter coupling. This can in principle be used to build single-photon sources and switches, both of which are important for quantum technologies. Unfortunately, the confinement of light using plasmonics comes at the expense of significant loss. Fortunately, recent studies have shown that with careful engineering one can overcome loss and even exploit it for realising quantum applications at the nanoscale. I will talk about some of these applications, many of which have been experimentally demonstrated, including quantum sensing, quantum random number generation, and the production and distillation of entanglement.

Heesuk Rho has been a faculty member of the Jeonbuk National University since 2002. He received a PhD in Physics from the University of Cincinnati and worked for two years as a Postdoc in Physics at the University of Illinois at Urbana-Champaign. His current research focuses on the optical and electrical properties of two-dimensional layered materials and devices through Raman scattering and photoluminescence utilizing state-of-the-art mapping facilities with microscale and nanoscale spatial resolution.

Two-dimensional layered structures have distinct types of defects such as wrinkles and bubbles. Such defects are formed in various sizes from the microscale to the nanoscale. Therefore, a precise control of spatial resolution is required to explore the optical properties of two-dimensional materials in the presence of defects. In this talk, we present Raman results of two-dimensional materials with micrometer and nanometer resolutions. Micro-Raman imaging of bubbles identified the spatial changes in charge density in monolayer WS2 under the influence of hexagonal boron nitride. Formation of wrinkles in WS2 at the nanoscale resulted in the splitting of the in-plane optical phonon into two singlet modes. Furthermore, tip-enhance Raman spectroscopy resolved spatial distributions of electron density across the wrinkled WS2 surface. Our study demonstrates that the control of spatial resolution is beneficial to understand the energy landscape of atomically thin defective materials. [This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Korea government (MSIT) (Grant Nos. 2019R1A2C1003366 and 2022R1A4A1033358)]

Dr. Yousoo Kim is a professor in the Department of Applied Chemistry at the University of Tokyo and the chief scientist at RIKEN. He obtained his Ph.D. from the University of Tokyo in 1999 and subsequently worked as a special postdoctoral researcher and senior research scientist at RIKEN. Dr. Kim's research focuses on nanoscale surface and interface science, with an emphasis on single-molecule chemistry and spectroscopy utilizing the scanning tunneling microscope.

The interaction between light and matter can be enhanced at the nanoscale due to the localized surface plasmon resonance. The localized light, known as near-field light, can be used to explore chemical reactions and spectroscopy based on the interaction between the near-field light and the electronic/vibrational quantum states of a single molecule. We developed an optical scanning tunneling microscope (STM) that combines the STM with light irradiation and detection technologies, which enables the application of near-field light for exploring the chemical reactions and spectroscopy at the STM junction. We have demonstrated single-molecule emission and absorption spectroscopy, visualization of energy transfer between two molecules, and single-molecule chemical dynamics using near-field light. We also measured the tip-enhanced resonance Raman spectra of a single molecule and an ultrahigh-energy resolution photoluminescence of a single molecule using a tunable excitation laser. These optical setups further enabled the real-space measurement of photocurrent pathways at a single molecule. In this talk, I will discuss recent issues focusing on single-molecule spectroscopy based on the excitation of molecular quantum states by near-field light at the STM junction.

Professor Bin Ren received his bachelor’s degree in 1992 and PhD degree in 1998 from Xiamen University and started independent research work in the same university after that. He is a Fellow of the International Society of Electrochemistry and recipient of Electrochemistry Award, Analytical Chemistry Division (ACS), AvH Fellow, National Science Fund for Distinguished Young Scholars. He serves as the Vice Dean of the College of Chemistry and Chemical Engineering,, Associate Editor of Analytical Chemistry (ACS). His research interest focuses on the development of new instruments and spectroscopic methods, mainly related to tip-enhanced Raman spectroscopy, surface-enhanced Raman spectroscopy, and nano-spectroelectrochemistry methods and their application in studying surface and interface processes and cell and biological systems. He is the principal investigator of The Innovative Research Group Project and National Major Scientific Instruments and Equipments Development Project of NSFC.

Tip-enhanced Raman spectroscopy (TERS), which combines scanning probe microscopy and plasmon-enhanced Raman spectroscopy, is capable of simultaneously obtaining the topographical and Raman fingerprint information at nanometer spatial resolution. Such a spatial resolution will allow the identification of the local physicochemical properties of different sites on the nanocatalysts without bothering the averaged effect in ensemble measurements, which makes it possible to disentangle the electronic effect and geometric effect with the change of the size. We visualized the size-specific electronic, geometric and catalytic properties of the different sites located on the individual Pd nanocatalyst by real-space TERS imaging with 3 nm spatial resolution. We further developed electrochemical tip-enhanced Raman spectroscopy (EC-TERS) for in situ monitoring the geometric and electronic evolution of individual active sites of MoS2 during hydrogen evolution reaction (HER) and revealed the progressive generation of active sites during the electrochemical activation and reaction processes. These discoveries offer new insights into our understanding of the active site and its dynamics during electrocatalytic processes.

Chemical doping plays an essential role in nanophotonics, particularly in improving the performance of TMD photodetector by suppressing the recombination rate of photocarriers in the channel layer. In this talk, we introduce our doping studies performed on several TMD devices (e.g., MoS2, WSe2, ReS2, and ReSe2) by meticulously analyzing key performance factors such as photoresponsivity, detectivity, and rising/decaying time. Our studies explain the fundamental mechanisms underlying the significance of doping techniques in enhancing the performance of TMD photodetectors. In addition, we introduce the intrinsic limitations of doping techniques and propose diverse solutions.

Geunchang Choi is an assistant professor of School of Electrical and Electronics Engineering at Chung-Ang University, South Korea. He received the B.S. degree in School of Electrical and Electronics Engineering from Chung-Ang University in 2010, M.S. degree in Electrical Engineering and Ph.D. degree in Physics from Seoul National University, South Korea in 2012 and 2018, respectively. After postdoc research at Sungkyunkwan and Ottawa University, he joined Chung-Ang University in 2021. His current research interests include all aspects of terahertz spectroscopy and metamaterial applications

Optical pump-terahertz probe technique based on femtosecond laser has been conducted in various semiconductor materials for measurements of carrier dynamics. As a probe beam, terahertz waves with low photon energy have many advantages such as being nondestructive and being far below the bandgap of the targeted semiconductor materials. On the one hand, terahertz nanoslot antennas have been studied for various applications, such as sensing and nonlinear effect, due to the advantage of background free, field enhancement, and field confinement. Combined with semiconductor materials, terahertz nanoslot antennas enable various semiconductor materials to have unique properties such as characterization and an ultrafast terahertz device.
Here, we will present terahertz nanoslot antenna applications for photo-excited semiconductor materials. Our results were enabled by the strong field confinement of the antenna, which interacts with semiconductor materials effectively. First, we will discuss the measurement of surface carrier dynamics of the bulk semiconductor materials by using the nanoslot antennas fabricated onto the semiconductor materials. After then, we will discuss the high on/off ratio and ultrafast terahertz modulation by the optical excitation of graphene/metal nanoslot antennas.

• 2022.03–current: Assistant Professor, Department of Physics, Sogang University, Seoul, Korea
• 2020.12–2022.02: Senior Researcher, Korea Institute of Science and Technology (KIST), Seoul, Korea
• 2020.09–2020.12: Post-doctor, Center for Subwavelength Nanowire Photonic Devices, Korea University, Seoul, Korea (Advisor: Prof. Hong-Gyu Park)
• 2018.08–2020.08: Post-doctor, Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK (Advisor: Prof. B. D. Gerardot)
• 2016.09–2018.07: Senior Engineer, Samsung Electronics

• 2008.02–2016.08: Ph. D., Department of Physics and Astronomy, Seoul National University, Seoul, Korea (Advisor: Prof. Gyu-Chul Yi)
• 2004.03–2008.02: B.S., Department of Physics and Astronomy, Seoul National University,

Van der Waals heterostructures can be designed to confine electrons and holes in unique ways. One remarkable approach is to vertically stack two atomically thin layers of transition metal dichalcogenide (TMD) semiconductors. The relative twist or lattice mismatch between the two layers leads to moiré pattern formation, which modulates the electronic band structure according to the atomic registry. Single-particle wave packets can be trapped in the moiré-induced potential pockets with three-fold symmetry, leading to the formation of trapped interlayer excitons and correlated states. In this talk, I will explain photoluminescence emission of moiré confined excitons in MoSe2/WSe2. Interesting properties of moiré excitons like antibunching, large Stark shift, and doping dependence will be presented. Furthermore, correlated states, such as Mott insulating states and Wigner crystals, observed from moiré heterostructures will be presented.

Jeong-Eun Park is an Assistant Professor at the Department of Chemistry, Gwangju Institute of Science and Technology (GIST) in Gwangju, Korea. She obtained her undergraduate degree in Chemistry (2010) from Pusan National University (Early Graduation, Graduation with Honors) and received her Ph.D. in Chemistry from Seoul National University in 2018 under the supervision of Prof. Jwa-Min Nam. She received two best Ph.D. thesis awards from both the Korean Chemical Society (KCS) and the Korean Academy of Science and Technology (KAST). After moving to Prof. Teri W. Odom’s group at Northwestern University for her postdoctoral study, she was appointed to the Department of Chemistry, GIST in 2022.
Jeong-Eun has worked on Plasmonics where she utilized noble/non-noble metals to develop nanostructures at multi-scales. In individual nanoparticle systems, she achieved precise structural control in the colloidal synthesis of plasmonic nanocrystals, which enhanced their optical properties. In two-dimensionally arranged nanoparticle lattice systems, she explored light−matter interactions between excitons and plasmons in different coupling regimes. She had 18 publications in high-profile journals including Nano Letters, ACS Nano, Nature Communications, and Advanced Materials. Her current research interests span from materials chemistry to nanophotonics.

Plasmonics utilize light-matter interaction at a dimension smaller than the wavelength of light. Due to their flexible shapes and geometries, metal-based plasmonic materials can be a reliable tool for obtaining desired plasmonic near- and far-field properties. In this talk, I will first introduce the highly controlled synthesis of gold nanoparticles [1, 2]. From their uniform structures and strong plasmonic effect, we achieved reproducible surface-enhanced Raman scattering signals and the highest metal photoluminescence quantum yield. In the second part, I will present collective nanoparticle-emitter hybrid systems. When nanoparticles are periodically arranged in two dimensions, diffractive coupling of plasmon modes from each nanoparticle generates surface lattice resonances [3]. By integrating plasmonic lattices with perovskites, we investigated unique optical feedback for lasing and ultrafast dynamics of strongly coupled perovskites [4, 5].

1994	Ph.D., Department of Physics, Ohio State University, OH., U.S.A.
1994 – 1995	Postdoc, Department of Physics, Ohio State University, OH., U.S.A.
1995 – present	Assistant, Associate, and Full Professor, Department of Physics, Korea University
2001, 2012	Visiting Professor, Department of Physics, Ohio State University, OH., U.S.A.
2007 – 2012	Director of National Research Lab (NRL) for Hybrid Nanostructures
2008 – 2016	Regional Editor of Synthetic Metals
2015 - present	Fellow, The Korean Academy of Science and Technology (KAST)

2006	Hyundai-KIA Chaired Professor in Natural Science
2008	National R&D 100 Excellent Research Award (KISTEP)
2008	National Research Award (Korea Research Foundation)

- Nanoscale optical and electrical properties of organic hybrid nanostructures
- Photoresponsive nano-devices using organic hybrid nanostructures
- Plasmonics and nanophotonics of hybrid nanostructures
- Charge transport of conducting polymers
- Electromagnetic interference shielding

1.”Far-Red Interlayer Excitons of Perovskite/Quantum-Dot Heterostructures”, T. J. Kim, S.-h Lee, E. Lee, C. Seo, J. Kim, J. Joo*, Advanced Science 2023, in press, DOI: 10, doi.org/10.1002/advs.202207653

2.”Temperature- and Power-Dependent Characteristics of Heterointerlayer Excitons Emitting in the Visible Region of a WS₂/PbI₂ Nanostructure: Implications in Excitonic Devices”, J. Y. Kim , T. J. Kim, S.-h. Lee, E. Lee, Jeongyong Kim, J. Joo*, ACS Appl. Nano Mater., Vol.5, p.11167 (2022).

3. “Charge-Transfer Effect and Enhanced Photoresponsivity of WS2- and MoSe2-Based Field Effect Transistors with pi-Conjugated PolyelectrolyteHybrid Characteristics of MoS₂ Monolayer with Organic Semiconducting Tetracene and Application to Anti-Ambipolar Field Effect Transistor”, D. Kwon, J. Y. Kim , S.-h. Lee, E. Lee, J. Kim, A. K. Harit, H. Y. Woo, J. Joo*, ACS Applied Materials & Interfaces, Vol.13, p.40880 (2021).

4. “Photovoltaic Field-Effect Transistors Using a MoS₂ and Organic Rubrene van der Waals Hybrid”, C. J. Park, H. J. Park, J. Y. Lee, J Kim*, C. H. Lee, and J. Joo*, ACS Applied Materials & Interfaces, Vol.10, p.29848 (2018).

5. “Significant enhancement of photoresponsive characteristics and mobility of MoS₂-based transistors through hybridization with perovskite CsPbBr₃quantum dots”, T. Noh, H. S. Shin, C. Seo, J. Y. Kim, J. Youn, J. Kim, K.-S. Lee, and J. Joo, Nano Research, Vol.12, p.405 (2019).

6. “Enhancement of photoresponsive electrical characteristics of multilayer MoS₂ transistor”, E. H. Cho, W. G. Song, C. –J. Park, J. Kim, S. Kim, and J. Joo*, Nano Research, Vol.8, p.790 (2015).

7. “Quantum dot and π-conjugated molecule hybrid: nanoscale luminescence and application to photoresponsive molecular electronics”, Y. D. Han, Y. -B. Lee, S. Park, S. Jeon, A. J. Epstein, J. -H. Kim, J. Kim, K. -S. Lee, and J. Joo*, NPG Asia Materials Vol.6, p.e103 (2014).

8. “Remote Biosensing with Polychromatic Optical Waveguide Using Blue Light-Emitting Organic Nanowires Hybridized with Quantum Dots”, E. H. Cho, B. -G. Kim, S. Jun, j. Lee, D. H. Park, K. -S. Lee, J. Kim, J. Kim, and J. Joo*, Advanced Functional Materials Vol.24, p.3684 (2014).

9. “Surface enhanced Raman scattering effect of CdSe/ZnS quantum dots hybridized with Au nanowire”, Y. –B. Lee, S. H. Lee, S. Lee, H. Lee, J. Kim*, and J. Joo*, Applied Physics Letters, Vol.102, p.033109 (2013).

10. “High-Detectivity Multilayer MoS₂ Phototransistors with Spectral Response from Ultraviolet to Infrared”, W. Choi, M. Y. Cho, A. Konar, J. H. Lee, G. Cha, S. C. Hong, S. Kim, J. Kim, D. Jena, J. Joo*, and S. Kim, Advanced Materials Vol.24, p.5832 (2012).

Heterostructures (HSs) using transition metal dichalcogenides, organic semiconductors, perovskites, and quantum-dots (QDs) are promising platforms for exciton-based photonics and optoelectronics. Distinctive interlayer exciton (ILX) emission at far-red region (1.42 eV) was realized for the perovskite MAPbI₃/CdSe-ZnS-QDs HS modulating energy band alignment through the diameter of QDs.¹ The photoinduced charge transfer (CT) of the MAPbI₃/CdSe/ZnS-QDs HSs was clearly observed for the insertion of thin h- BN layer and for thin ZnS shell barrier of QDs. The intense and broad PL emission of ILX of the HS using monolayer WS₂ and multilayer PbI₂ was also observed in visible light region at 675-700 nm at low temperatures.² The drastic decrease in PL intensity of the WS₂/PbI₂ HS indicates the occurrence of CT with type-II band alignment. The characteristics of ILXs of the WS₂/PbI₂ and MAPbI₃/CdSe-ZnS-QDs HSs are compared to those of the intermolecular excitons (IMXs; i.e., exciplexes) and ILXs in the HS consisting of organic donor (m-MTDATA) and acceptor (T2T) molecules. For ILXs of various HSs studied here, PL peaks were blue-shifted with increasing excitation power, originating from the screening effect of Coulomb repulsive interaction between dipole- aligned ILXs. The lifetime of ILXs of the HSs was considerably longer than that of pristine excitons. Back focal plane imaging suggests that the directions of dipole moments of the ILXs at the interfaces are relatively out-of-plane compared to those of intralayer excitons.

2007: B.Sc. and M.Sc. in Optoelectronics at Bauman Moscow State Technical University
2009: M.Sc. in Electrical Engineering at Seoul National University
2009–2012: senior researcher, Samsung Electronics
2017: Ph.D. in Electrical Engineering at Seoul National University
2017–2021: post-doc, KAIST
2021–present: research professor, KAIST
Areas of interest: nanophotonics, near-field probing

Polaritons – hybrid quasi-particles of light coupled to the collective oscillations of charges – provide an exceptionally high degree of field confinement and a capability for light manipulation at nanoscale. Very recently, a new class of ultra-compressed polaritonic modes in van der Waals crystals has been spotlighted as a superior platform for a strong light-matter interaction: the ‘image’ polaritons, supported by a polaritonic material in proximity to a metal when the polaritonic mode couples with its mirror image.
We use scanning scattering-type near-field optical microscope (s-SNOM) to study the hyperbolic ‘image’ phonon-polaritons in hexagonal boron nitride (hBN) and orthorhombic molybdenum trioxide (α-MoO₃) crystals at mid-infrared frequencies. Atomically-flat monocrystalline gold flakes are used as a substrate, practically eliminating the surface-mediated scattering of propagating polaritonic modes. Furthermore, ~20 um-long sharp gold edges efficiently launch polaritons with a planar wavefront. In such system, polariton properties can be accurately measured by the real-space mapping of their near-field interference with the excitation beam. Besides, gold substrate guarantees the maximum signal-to-noise ratio of the s-SNOM output signal, providing ideal conditions for near-field experiments at mid-infrared frequencies.

2018	Ph.D. in Physical Chemistry, Xiamen University, China Dissertation: Light-matter interactions in confined spaces at the nanoscale – from surface plasmons to two-dimensional excitons Advisors: Prof. Bin Ren, Prof. Zhong-Qun Tian
2013	B.S. Chemistry, Xiamen University, China

2023.01 – present	Professor, Department of Chemistry, Xiamen University, China
2020.01 – 2022.12	Staff scientist (Akademischer Rat a.Z.), Department of Physics, University of Regensburg, Germany
2018.05 – 2019.12	Postdoctoral fellow, Department of Physics, University of Regensburg, Germany (Supervisor: Prof. John M. Lupton)
2017.04 – 2018.02	Visiting research fellow, Department of Physics, University of Regensburg, Germany (Host: Prof. John M. Lupton)
2016.03 – 2016.09	Visiting research fellow, University of Colorado at Bounder/JILA, USA (Host: Prof. Markus B. Raschke)
2014.07 – 2014.08	Visiting research fellow, Donostia International Physics Center (DIPC), Spain (Host: Prof. Javier Aizpurua)

2023	Walter-Schottky-Preis.
2019	Selected Young Scientist for the 69th Nobel Laureate Meeting in Lindau (Poster presentation).
2018	Outstanding Ph.D. Thesis Award in Fujian Province.

Period	Funding source	Amount	Role
2021-2025	German Research Foundation (DFG), SFB 1277, B11	~300 k€	PI
2021-2023	Sino-German Center, Mobility Programme M-0153	~135 k€	PI
2020-2023	German Research Foundation (DFG), SPP 2244, LI 3725/1-1	~232 k€	PI

Science, Nature Communications, Light: Science & Applications, Journal of the American Chemical Society, Optical Express, npj 2D Materials and Applications, The Journal of Physical Chemistry, Langmuir

Outstanding reviewer in 2021 for Light: Science & Applications.

Experimental Condensed Matter physics/Quantum Nonlinear Optics/Ultrafast Spectroscopy

Plasmonics/Raman spectroscopy/Plasmon-enhanced Raman spectroscopy

Two dimensional semiconductors such as transition-metal dichalcogenide (TMDC) monolayers show a wealth of exciton physics. We present the existence of a novel excitonic species, the high-lying exciton (HX), in TMDC monolayers with almost twice the energy of the band-edge A-exciton but with a linewidth as narrow as that of band-edge excitons. The HX is populated through momentum-selective optical excitation in the K-valleys, and is identified experimentally in upconverted photoluminescence and theoretically in ab initio GW-BSE calculations. These calculations show that the HX is comprised of electrons of negative effective mass. The coincidence of such high-lying excitonic species at around twice the energy of band-edge excitons gives rise to a well-defined excitonic three-level system, which enables quantum-interference phenomenon revealed in optical second-harmonic generation. We show that the temporal dynamics in such a three-level system can be probed through time-resolved sum-frequency generation and four-wave mixing. The HXs can also be tuned over a wide range by twisting and Stark effect in bilayer WSe₂, which gives control over the excitonic quantum interference and the corresponding optical nonlinearities. Finally, we show how an electrical gate can be used to tune excitonic quantum interference in a monolayer TMDC transistor device by forming trions.

Speaker biography Hui-Hsin Hsiao received the B.S. degree in Physics and the Ph.D. degree in Graduate Institute of Photonics and Optoelectronics (GIPO) from National Taiwan University (NTU), Taiwan, in 2007 and 2013, respectively. From 2013 to 2015, she was a postdoctoral researcher in GIPO. In the period of 2015 to 2016, she joined in Institute of Theoretical Solid State Physics at Karlsruhe Institute of Technology, Germany, as a postdoctoral researcher. She was with Department of Physics at NTU as a postdoctoral research fellow from 2016 to 2017. She became an assistant professor in Graduate Institute of Biomedical Optomechatronics at Taipei Medical University in 2017. In 2018, she joined the faculty of Institute of Electro-Optical Engineering at National Taiwan Normal University (NTNU) and was promoted as an associate professor in 2021. In 2022, she joined the faculty of Department of Engineering Science and Ocean Engineering at National Taiwan University as an associate professor.

Her research interests include linear and nonlinear plasmonics, nanophotonics, mid-infrared thermal emitters, metamaterials and metasurfaces, and optoelectronic devices. She has published 40 SCI journal papers including Advanced Materials, Advanced Science, Nano Letters, Small Methods, Small, Laser and Photonics Reviews, Advanced Optical Materials, ACS Photonics, Sensors & Actuators: B. Chemical, etc. She received several research awards and recognition from different government and professional organizations, including Chieh-Shiung Wu Fellowship of the Physical Society of the Republic of China in 2014, Postdoctoral Research Abroad Program scholarship from the Ministry of Science and Technology in 2014, Best Research Paper Award for Postdoctoral Fellows in 2015, and Youth Photonics Award of Taiwan Photonics Society in 2022.

Metasurfaces have opened a whole new paradigm for controlling electromagnetic waves in unprecedented ways, intriguing various novel optical effects and applications. A variety of polarization-multiplexing metadevices have been developed for versatile applications. Several pioneering works utilized integrated resonant units (IRUs) designs, which combine multi-nanorod configuration into one unit cell, to successfullly tailor phase dispersion and efficiency enhancement for circular-polarized light over a continuous broad spectral range.

In this work, we developed a broadband high efficiency polarized beam splitting (PBS) metagrating based on IRU designs to simultaneously enable polarization analysis, spectral dispersion, and spatial imaging in the near infrared. The PBS metagratings spatially separate the linear-polarized (LP) light into four orthogonal polarization states (0°, 90°, 45°, and 135°). Through the near-field coupling of multiple nanobricks, the hybridized mode in IRUs achieve a broadband reflection efficiency enhancement and retain the required phase value with a linear and smooth phase dispersion for the co-polarized light. The IRU-based PBS metagrating shows an ultra-broadband efficiency enhancement from wavelengths of 600 nm to 1100 nm outperforming their single-rod counterparts. Our findings establish a robust basis for building up ultrabroadband high efficiency metadevices and foster the applications of versatile metadevices.

Hong Wei is a professor at Institute of Physics, Chinese Academy of Sciences. She received her Ph.D. in condensed matter physics from Chinese Academy of Sciences in 2009. Her research interests focus on plasmonics and nanophotonics. She is a recipient of the Chinese Young Female Scientist Award. She was a topical editor of Journal of the Optical Society of America B from 2017 to 2023. She is a member of the editorial board of Journal of Optics, Advanced Photonics Research, and Advanced Physics Research.

The strong coupling between excitons and single plasmonic nanocavities enables plexcitonic states in nanoscale systems at room temperature. Here we demonstrate the strong coupling of surface plasmon modes of metal nanowires and excitons in monolayer semiconductors, with Rabi splitting manifested in both scattering and photoluminescence spectra. By utilizing the propagation properties of surface plasmons on the nanowires, the photoluminescence emitted through the scattering of plasmon-exciton hybrid modes is extracted. The analytically calculated scattering and photoluminescence spectra well reproduce the experimental results. These findings unify the scattering and photoluminescence spectra in the plexcitonic system and eliminate the ambiguities of photoluminescence emission, shedding new light on understanding the rich spectral phenomena in the plasmon-exciton strong coupling regime.

Zhen-Chao Dong received his BS from Sichuan University in 1983, MS from Xiamen University in 1987, and PhD from Fujian Institute on the Structure of Matter, Chinese Academy of Sciences in 1990. He went to Iowa State University as a postdoctoral research associate in 1992. From 1996 to 2004, he worked at National Institute for Materials Science (NIMS) in Japan as Senior Researcher and Sub-Theme Leader. Since 2004, he is a full professor in Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China. His recent research interests are in the field of single-molecule optoelectronics and nanoplasmonics, particularly on STM based single-molecule Raman scattering, single-molecule electroluminescence and photoluminescence as well as energy transfer at the single-molecule level, all achieving spectro-microscopic imaging down to the sub-nanometer scale.

Aspirations for reaching atomic resolution with light have been a major force in shaping nano-optics, whereby a central challenge is to achieve highly localized optical fields. The plasmonic nanocavity defined by the coinage-metal tip and substrate in a scanning tunneling microscope can provide highly confined and dramatically enhanced electromagnetic fields upon proper plasmonic resonant tuning. In this talk, I shall demonstrate two recent STM-based phenomena related to single-molecule optical spectroscopy. The first is single-molecule Raman scattering. The spatial resolution of tip enhanced Raman spectroscopy has been further driven down to the Angstrom scale at the single-bond level. Such a capability not only yields a new methodology called scanning Raman picoscopy for structural reconstruction and tracking bond breaking and forming of surface reactions, but also enables to clarify the chemical enhancement mechanism in TERS through well-controlled local contact environments. The second phenomenon is single-molecule electroluminescence. Through managements over molecular quenching and energy level alignment, we demonstrate clear single-molecule electroluminescence and even single-photon emission. Furthermore, by precisely controlling intermolecular distances, we can not only demonstrate coherent dipoledipole coupling in homodimers, but also reveal intriguing transitions from incoherent hopping-like Forster energy transfer to coherent wavelike electronic energy transfer in donoracceptor heterodimers.

Plasmonic nanostructure based on silver and gold that produces LSPR to withstand ultrahigh temperatures without damage remains a great challenge for future ultra-compact integrated circuits, and high-power enabled photonic devices. In principle, the shapes of plasmonic nanostructures containing noble metals would change after the heat treatment that altered the plasmonic resonance. Thus, discovering refractory plasmonic materials that can exhibit plasmonic resonance in the visible range is essential. A challenge in refractory plasmonic materials is the bulk plasmon frequency is usually in the near-infrared range, making it difficult to generate plasmonic colors in the visible. We first reported a new refractory plasmonic material HfN, one of the conductive nitrides, that has a relatively high bulk plasmon frequency (λ = 400 nm) with a high melting point (T ∼ 3583 K) and a relatively large magnitude of the real part of the permittivity, which enables intense local electromagnetic field confinement to form LSPR in the visible region. We use this unique property to develop full-color plasmonic pixels with sub-diffraction resolution through tailoring HfN plasmonic crystals and demonstrate that HfN refractory plasmonic crystals can withstand high-temperature annealing (900 °C) without damage. The novel HfN refractory plasmonic materials unlock new opportunities for ultra-compact integrated functional plasmonic devices. Especially the unique property of HfN, implying a bright future for emerging plasmonic materials at visible wavelengths [1]. In addition, I will present an overview of my research works over the past five years on the plasmon-enhanced light-matter interactions in the visible regions and their applications [1-6], including the plasmonic nanolasers [2-3], tunable plasmonic modulators [4], plasmonic phototransistors [5], plasmon-enhanced solar energy harvesting [6], and the refractory plasmonic colors for back-light free displays [1]. My group discovered several unique working mechanisms that utilize plasmonic nanocavities to improve optoelectronic device performance. By engineering the local electromagnetic field confinement, the light-matter interaction strength can be enhanced, which results in efficient energy conversion in the designed nanosystem. Moreover, I will discuss the detailed mechanisms and possible applications. These results have broad implications for the use of alternative plasmonic nanocavities in high-performance optoelectronic devices.

• Ph.D. (2007): Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Japan
• M. S. (2004): Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Japan
• B. S. (2002): Department of Bioscience and Biotechnology, Tokyo Institute of Technology, Japan

• 2022.8 – present: Visiting Associate Professor, Department of Applied Chemistry, National Yang Ming Chiao Tung University, Taiwan
• 2017.9 – present: Associate Professor, Research Institute for Electronic Science, Hokkaido University, Japan
• 2011.4 – 2017.8: Assistant Professor, Research Institute for Electronic Science, Hokkaido University, Japan
• 2009.6 – 2011.3: Post Doctoral Fellow, Research Institute for Electronic Science, Hokkaido University, Japan
• 2007.6 – 2009.5: Post Doctoral Fellow, Department of Chemistry, Lehigh University, USA
• 2007.4 – 2007.5: Post Doctoral Fellow, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Japan
• 2004.4 – 2007.3: Research Fellowship for Young Scientists (DC1), Japan Society for the Promotion of Science, Japan

Gold nanoparticles have attracted attentions in various research fields due to their useful optical properties, known as Localized Surface Plasmon Resonance (LSPR). Rod-shaped gold nanoparticles (gold nanorods: GNRs) show two LSPR modes due to their anisotropy; One is Transverse LSPR (T-LSPR) at about 500-600 nm, and the other one is Longitudinal LSPR (L-LSPR) in the near-infrared region. As this L-LSPR is quite strong and sensitive compared to that in spherical AuNPs, an effective use of this L-LSPR is important. Due to their angle dependence toward incident light and gap distance dependence between particles, arrangement of GNRs has been a significant issue. Although various GNR alinement were fabricated on the substrate via top-down and bottom-up approaches, the active control of GNR arrangement on substrates remains challenging. In this talk, I will show our approach using polymer brushes as a substrate. First, we developed a preparation method for the vertically aligned GNR arrays on DNA-modified substrates as a soft template. Then, we demonstrated active orientation control of GNRs on polymer brush substrates. Further, assembly/disassembly of vertically oriented GNRs on polymer brush substrates are also confirmed.

Kentaro Iwami was born in Miyagi prefecture, Japan. In 2003, he graduated from Tohoku University (School of Eng., Dept. Mechatronics and Precision Eng.). In 2008, he completed his doctorate studies (Grad. School of Eng., Dept. Nanomechanics). He became a JSPS Research Fellow (DC1) in 2005, an assistant professor at the Tokyo University of Agriculture and Technology (Grad. School of Eng., Dept. Mech. Syst. Eng.) in 2008, and a visiting scholar at Stanford University in 2011. Since 2012, he has been an associate professor at the Tokyo University of Agriculture and Technology (Grad. School of Eng.). His research interests are NEMS/MEMS using metasurface plasmonics. Membership: JSME. JSAP, IEEJ, OSJ, IEEE, SPIE, and ACS.

Metasurfaces based on dielectric nanostructures have attracted much attention due to their potential applications in a wide range of wavefront and polarization conversion. Dielectric nanopillar meta-atoms utilize propagation phase delay, which offers high transmittance in the visible and infrared regions. In addition, the negative correlation between the bandgap and the refractive index makes pillars tall for the short wavelengths. We adopt silicon and silicon nitride for infrared and visible meta-atom material. In this study, we introduce the design theory and fabrication methods of our recent achievements in dielectric metasurface: rotational varifocal metasurface lenses (metalenses), multifunctional prism-quarter waveplate metasurface for chip-scale atomic clocks, and multicolor metasurface holographic movies. The rotational varifocal metalens achieves a wide range of focal length adjustment from convex to concave. The multifunctional prism-quarter waveplates achieved high diffraction efficiency over diffraction gratings. Metasurface holograms achieved multicolor animation at the maximum reproduction speed of 30 frames per second through a cinematographic approach.

Prof. Okamoto received his Ph.D. degree in Chemistry from Kyoto University, Kyoto, Japan, in 1998. From 1998 to 2000, he was a researcher at the Venture Business Laboratory of Kyoto University and from 2000 to 2002, he was a Research Fellow of the Japan Society for the Promotion of Science (JSPS). He then worked as a Postdoctoral Scholar of Electrical Engineering at the California Institute of Technology from 2001 to 2005, where he was a Senior Research Fellow of Physics from 2005 to 2007. From 2007 to 2011, he was a Research Associate Professor of Electronic Science and Engineering at Kyoto University, and from 2011 to 2018, he was an Associate Professor at the Institute for Materials Chemistry and Engineering at Kyushu University. Since 2018, he has been a Professor in the Department of Physics and Electronics at Osaka Prefecture University, which changed its name to Osaka Metropolitan University in April 2022 due to university integration. His current research interests include developing new optical materials and devices based on nanophotonics and plasmonics.

One futuristic application of plasmonics is the development of high-efficiency light-emitting diodes (LEDs). In 2004, we presented the first report of large photoluminescence (PL) enhancements for InGaN/GaN quantum well (QW) materials coated with Ag thin films.
The next important challenge is the extension of the SP resonance into the UV and IR wavelength regions for wider applications. By using aluminum, we succeeded in achieving 7-fold enhancements of deep UV emissions around 260 nm from AlGaN/AlN QWs. We also succeeded in controlling the SP resonance based on random metallic nanostructures on a mirror to tune the optical properties in the visible, deep UV, and near IR wavelength regions. These flexibly tunable optical properties are envisaged to lead to the development of new applications and technologies in the field of plasmonics and nanophonics.
We also found a novel method to improve the emission efficiencies of InGaN/GaN by depositing dielectric thin films instead of metals and using UV laser irradiation. This makes it easy to apply to LED devices that do not require a special structure to extract light. With such advancements, this technology will pave the way for highly advanced light-emitting devices, such as highly efficient RGB LEDs and micro-LED displays.

Makoto Naruse received Ph.D. degree in Engineering from the University of Tokyo in 1999. He joined the National Institute of Information and Communications Technology, Ministry of Internal Affairs and Communications, Tokyo, in 2002. Since 2019, he has been a Professor with the Department of Information Physics and Computing, Graduate School of Information Science and Technology, the University of Tokyo. He has been involved in the field of information physics and computing, especially in photonic computing by means of advanced photonics including near-field optics.

Decision-making is important in information and communication technology and artificial intelligence. Here we present some photonic approaches to decision-making using quantum and near-field light. We show single photon-based systems to solve multi-armed bandit problems by utilizing wave-particle duality for exploration. Furthermore, we demonstrate that entanglement and quantum interference are useful for social decision-making, whereby the expected value regards maximizing social benefits and ensuring fairness among individuals. In the meantime, complex spatiotemporal light correlations induced in the subwavelength scale become precious resources for problem-solving. We demonstrate an order recognition algorithm driven by versatile optical near-field patterns generated in photochromic materials.

Dr. Satoshi Ashihara is a Professor at Institute of Industrial Science (IIS) in the University of Tokyo, Japan. He earned his PhD from the University of Tokyo in 2003 and went on to visiting research at Max-Born-Institute in Germany. After working as an Associate Professor at Tokyo University of Agriculture and Technology in Japan, he joined IIS, the University of Tokyo in 2014. His research interest lies in short-pulsed lasers, plasmonics, and ultrafast light-matter interactions.

Ultrashort infrared pulses are useful not only for nonlinear vibrational spectroscopy but also for multi-step vibrational excitation toward active control over molecular processes at electronic ground states. Surface plasmons in the infrared range provide a new platform for these nonlinear vibrational processes because they substantially strengthen the interaction between an infrared photon and a molecular vibration.
In recent years, we have applied infrared plasmonics to strong-field nonlinear phenomena, nonlinear vibrational spectroscopy, and vibration-mediated chemical reaction control. In particular, the we utilized plasmonic near-field enhancements to strongly drive molecular vibrations and thereby realized bond-breaking of condensed-phase molecules. In this talk, I will present recent progress and prospects of nonlinear light-matter interaction using nano-confined intense infrared fields.

Sunae So is an Assistant Professor at the Department of Electro-Mechanical Systems Engineering at Korea University- Sejong Campus. She received her B.S. (2016) and Ph.D. (2022) in Mechanical Engineering at Pohang University of Science and Technology (POSTECH), Korea. From 2022 to 2023, she was a postdoctoral researcher in the Graduate School of Artificial Intelligence at POSTECH. Her research interests include nanophotonics, optical metamaterials and metasurfaces, and inverse design. She has published more than 30 peer-reviewed articles, and she has also received numerous awards and honors for her work, including SPIE Photonics Scholarship.

Metaphotonics has enabled the realization of advanced optical technologies with ultra-thin devices, but the design of metaphotonics for desired optical properties remains a challenge. In this presentation, we propose an inverse design method for designing single-cell metasurfaces with tailored optical properties for multicolor and 3D holography [1]. Our approach leverages a gradient-descent optimization method to encode multiple pieces of holographic information into a single phase profile, demonstrating the state-of-the-art data capacity of a single-cell metasurface. Specifically, we design and experimentally demonstrate both multiplane RGB color and 3D holography using low-loss materials of TiO2. Our work provides an effective and systematic approach for designing metaphotonics with desired optical properties, and has potential applications in various areas, including imaging, sensing, and communication. The proposed inverse design method using single-cell metasurfaces could pave the way for the development of next-generation optical devices with enhanced performance and functionality.

[1] S. So, J. Kim, T. Badloe, C. Lee, Y. Yang, H. Kang, J. Rho, Adv. Mat. 35, 2208520 (2023)

When under stress, plants release molecules to activate their defense system [1,2]. Detecting these stress-related molecules offers the possibility to address stress conditions and prevent the development of diseases. However, detecting endogenous signaling molecules in living plants remains challenging due to low concentrations of these analytes and interference with other compounds. Here we demonstrate a SERS-based nanosensor for the real-time detection of multiple stress-related endogenous molecules in living plants. The nanosensor particles are consisted of corrugated Ag nanoshell on silica nanosphere of ca. 200 nm modified by a water-soluble cationic polymer poly(diallyldimethylammonium chloride) (PDDA), which can interact with multiple plant signaling molecules and are optically active in the near-infrared region (785 nm) to avoid interferences from plant autofluorescence. We measured a SERS enhancement factor of 2.9×107 and signal-to-noise ratio of up to 64 with an acquisition time of ~100 ms. To show quantitative multiplex detection, we adopted a binding model to interpret the SERS intensities of two different analytes bound to the SERS hot spot of the nanoprobe. Under either an abiotic or biotic stress, our optical nanosensors can successfully monitor salicylic acid, extracellular adenosine triphosphate, cruciferous phytoalexin, and glutathione in Nasturtium officinale, Triticum aestivum L., and Hordeum vulgare L., all stress-related molecules indicating the possible onset of a plant disease [3]. We believe that plasmonic nanosensor platforms can enable early diagnosis of stress, contributing to a timely disease management of plants.

In this talk, we present our recent work on the nanostructural optical antennas for functional devices, such as mix nanoantenna array for fluorescence enhancements, imaging of the inaccessible bound-states-in-the-continuum (BIC) mode, quasi-BIC resonance for enhancing cathodoluminescence (CL) emission, the highly saturated red color pixels, color-sensitive miniaturized detectors, tunable color pixels, as well as the plasmonic resonances of Si nanostructures at ultra-violet (UV).

Quasi-2D layered perovskites have recently attracted enormous interest as light emitters due to their outstanding photophysical and electrical properties. Due to their inherent quantum confinement and reduced dielectric screening, layered perovskites offer strong exciton binding energy and subsequent stable excitonic medium even at the room temperature. Mixed halide perovskites, however, suffer from significant spectral instability which obstructs their utilization for the light-emitting diodes. We found that the different activation energies required for directional ion hopping lead to the redistribution of anions during the device operation and suggested that the dominant red emission is ascribed to the thermodynamically favorable selective hole injection. Next, solution-processed quasi-2D perovskites contain multiple quantum wells and often exhibit a broad width distribution. To overcome these limitations, it is important to control quantum well dispersity. Modulation of film formation kinetics has paved the way for developing deep-blue emissive quasi-2D perovskites. Inhomogeneity of solution-processed quasi-2D perovskites results in the charge funneling into the smallest bandgap components, which hinders deep-blue emission and accelerates Auger recombination. We introduce a universal synthetic strategy to narrow the width distribution of perovskite quantum wells.

In the field of nanophotonics that employs two-dimensional materials, a major obstacle is the weak interaction between light and matter due to the mismatch in size between the thickness of the material and the wavelength of light in free space. However, we have successfully demonstrated a way to couple incident radiation to surface polaritons in two-dimensional materials with almost perfect efficiency. This high level of efficiency was achieved by using a two-stage polariton coupling mechanism, a photon-recycling device architecture, and a fabrication process that ensures an atomically smooth interface between the substrate and graphene. Our findings offer promising prospects for the development of nanophotonic devices that rely on two-dimensional materials and achieve high levels of optical efficiency.

Dr. Jinwei Zeng is currently an Associate Professor in Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology. He received his Bachelor’s Degree in Optoelectronics Engineering from Huazhong University of Science and Technology (China) in 2007, and PhD degree in Electric Engineering from the State University of New York at Buffalo (U.S.) in 2014. After that he worked as Postdoc Scholar in Missouri University of Science and Technology from 2015-2016, and in University of California Irvine from 2016-2018. He joined Huazhong University of Science and Technology as a faculty member from 2019 till present.
His research interest is mainly in the sciences and applications of Nano-photonics, including metamaterials/metasurfaces, structured light, photo-induced force microscopy, optical magnetism etc. In recent years, he has published more than 20 papers including the first author’s works in Science Advances, ACS Nano, ACS Photonics, Nano Letters, Journal of Lightwave Technology etc as the representatives of his researches in this field.

Optical magnetism describes matter’s response to the magnetic field of light, which is typically weak in nature. However, efficient exploitation of the optical magnetism can be the important foundation to make the future advanced opto-magnetic devices such as high-speed magnetic storage or high-resolution magnetic imaging. We investigate the optical magnetism through direct detection of the photo-induced magnetic force on a magnetic nanoprobe magnetically excited by structured light. This talk will also introduce the principle and feature of the photo-induced force microscopy (PiFM) as an important tool for near-field optical characterization using structured light.