Prof. Seok Ho Song

Office: Natural Science Building, Room# 410

Address: Department of Physics, Hanyang University,

Wangsimni-ro 222, Songdong-gu, Seoul 04763, South Korea

Phone: +82-2-2220-0923 E-mail:




Non-Hermitian (Complex-index) Nanophotonics Layout of Optics Lab



Our recent research activities are mainly focused on Non-Hermitian (NH) Nanophotonics that expands the conventional resonance-based nanophotonics to the conceptually far-reaching open-system domains where various unusual physical effects take place with manifestation of anti-linear symmetry groups, exceptional-point singularities, topological parametric structures, complex energy-spectral chirality, and associated broadband time-asymmetric operations. We explore, in both theory and experiments, various strongly-interacting open-system configurations provided by optical gains, losses, scattering, radiative inter-modal coupling, and mixed direct/indirect feedback structures.


The previous nanophotonics researches are conventionally on optical properties of nanostructured systems on a 2-dimensional plane of real permittivity and real permeability (εreal, μreal). Here, imaginary parts of permittivity and permeability (εimag, μimag) are regarded as minor factors that only cause monotonic amplification or attenuation of light. There have been numerous technological discoveries and advances in this viewpoint that treats nanophotonic systems as governed by the conventional Hermitian Hamiltonians. However, it has many limitations for applications in practice, such as narrow operation band, high loss properties, and reciprocity restrictions, to mention just a few.


If we extend the two-dimensional permittivity and permeability plane into a three-dimensional complex space as shown on the right-hand side of the left Figure, dynamics describing photonic systems follow non-Hermitian (NH) Hamiltonians in general and can cause completely new properties which do not appear in the Hermitian systems. For example, spontaneous symmetry-breaking phase transition, exceptional-point (EP) singularities, and associated unusual effects are presently attracting a great deal of academic attention along this line. Our proposal on the NH nanophotonics is strongly motivated in this consideration and we expect new device-operation principles and concomitant applications because of unique characteristics of NH systems including non-conserving nature (loss compensation or quantum-jump-like selection of least attenuating states), broadband properties of topological effects (dynamically encircling an EP), and unidirectional properties (one-way diffraction, reflection, absorption, and transmission), in stark contrast to the conventional Hermitian nanphotonics grounded in essentially frequency-selective coherent multiple-scattering and subsequent localization effects.


Our research aims to establish pioneering subjects pertaining to unexplored territories between non-Hermitian quantum mechanics and conventional nanophotonics technology. Toward this end, we introduce NH dynamics for open quantum systems as a new theoretical tool, explore complex-valued potential configurations realized in photonics systems, potentially discover new NH-photonic properties, and finally establish robust foundations of NH nanophotonic structures and elements as a promising device class for the next generation optical systems in numerous technology areas.



BD15276_Prof. Song

(1984) BS, Dept. of Physics, Yonsei University, Seoul, Korea

(1989) Ph.D, Dept. of Physics, KAIST (Korean Advanced Institute of Science and Technology), Seoul, Korea

(1989-1997) Senior Researcher, ETRI (Electronics and Telecommunication Research Institute), Korea

(1997-present) Professor, Department of Physics, Hanyang University, Seoul, Korea


BD15276_Post Doc.

(Dr. Youngsun Choi), Non-Hermitian photonics

(Dr. Jongkyun Hong), Non-Hermitian electronic circuits for photonics



(Gunpyo Kim), Non-Hermitian photonics

(Minjeong Kim), Non-Hermitian 2nd stopband photonics

(Hyungju Rah), 3D waveguide display

(Younghwa Ryu), Geometric-phase micro-nano optics

(Jonghyuk Park), Geometric-phase non-Hermitian Optics

(Kwangwuk Yu), Non-Hermitian topological photonics

(Kiyoung Lee), Non-Hermitian photonics

(Seungmin Lee), 3D projection display

(Wontae Im), Diffractive optical elements for display

(Jaewoong Ko), Non-Hermitian topological photonics

(Jiwon Ahn), Geometric-phase optics

(Jaesung Jeong), Diffractive optics for laser applications



BD15276_Lectures on Nanophotonics

2019-Introduction to Nanophotonics

1-Second-order stopband and leaky-mode resonator

2-GMR and Topological Photoncs

3-Optical properties of materials-dielectrics and metals

4-Dispersion relation of surface plasmon-polaritons

5-SPP Excitation

6-EM energy density in metals

7-Localized particle plasmons

8-Dispersion relation of metal nanorods and nanotips

9-Dispersion relation of SPPs on thin metal films

10-Dielectric loaded SPP waveguides

11-Metal-Insulator-Metal plasmonic slot-waveguides



BD15276_Special Lectures on Micro-optics, Nano-optics, and SPP Technologies

1.     Micro- and nano-optics based on diffraction effect for next generation technologies

2.     Guided-mode resonance (GMR) effect for filtering devices in LCD display panels

3.     Surface-plasmons: A basic

4.     Surface-plasmon waveguides and biosensor applications

5.     Efficient light emission from LED, OLED, and nanolasers via surface-plasmon resonance

6.     SPP on real metals

7.     SPP on metal-insulator-metal, metal nanorods, metal nanotips

8.     SPP Photovotaics


BD15276_Recent Papers

l  Choloong Hahn, Maude Amyot-Bourgeois, Howard Northfield, Youngsun Choi, Seok Ho Song, R. Niall Tait, and Pierre Berini, Nanofabrication of plasmonic structures on insulating substrates by resist-on-metal bilayer lift-off, Nanotechnology 30, 054003 (December 2018). Abstract

l  Jeong Yub Lee, Yongsung Kim, Seunghoon Han, Jaekwan Kim, Jae Woong Yoon, Ki Young Lee, Seok Ho Song, Kiyeon Yang, and Chang Seung Lee, CMOS-compatible Si metasurface at visible wavelengths prepared by low-temperature green laser annealing, Nanotechnology 30, 045301 (November, 2018). Abstract

l  Joong-Sung Lee, Seung-Jin Yoon, Hyungju Rah, Mark Tame, Carsten Rackstuhl, Seok Ho Song, Changhyoup Lee, and Kwang-Geol Lee, Quantum plasmonic sensing using single photons, Opt. Express 26, 29272 (Oct. 2018). Abstract

l  Jae Woong Yoon, Youngsun Choi, Choloong Hahn, Gunpyo Kim, Seok Ho Song, Ki-Yeon Yang, Jeong Yub Lee, Yongsung Kim, Chang Seung Lee, Jai Kwang Shin, Hong-Seok Lee, and Pierre Berini, Time-asymmetric loop around an exceptional point over the full optical communications band, Nature 562, 86 (September 2018). Abstract

l  Youngsun Choi, Choloong Hahn, Jae Woong Yoon, and Seok Ho Song, Observation of an anti-PT-symmetric exceptional point and energy-difference conserving dynamics in electrical circuit resonators, Nature Commun. 9, 2182 (June 2018). Abstract

l  Jae Woong Yoon, Seong-Min Ma, Gun Pyo Kim, Yoonshik Kang, Joonseong Hahn, Oh-Jang Kwon, Kyuyoung Kim and Seok Ho Song, Nanophotonic identification of defects buried in three-dimensional NAND flash memory devices, Nature Electronics 1, 60-67 (First issue, January 2018). Abstract


l  Suntak Park, Bongje Park, Saekwang Nam, Sungryul Yun, Seung Koo Park, Seongcheol Mun, Jeong Mook Lim, Yeonghwa Ryu, Seok Ho Song, and Ki-Uk Kyung, Electrically tunable binary phase Fresnel lens based on a dielectric elastomer actuator, Optics Express 25, 23801 (October 2017). Abstract

l  Ki Young Lee, Jae Woong Yoon, Seok Ho Song, and Robert Magnusson, Multiple p-n junction subwavelength gratings for transmission-mode electro-optic modulators, Scientific Reports 7, 46508 (April 2017). Abstract

l  Youngsun Choi, Choloong Hahn, Jae Woong Yoon, Seok Ho Song, and Pierre Berini, Extremely broadband, on-chip optical nonreciprocity enabled by mimicking nonlinear anti-adiabatic quantum jumps near exceptional points, Nature Commun. 8, 14154 (January 2017). Abstract


l  Choloong Hahn, Elham Karami Keshmarzi, Seok Ho Song, Cha Hwan Oh, R. Niall Tait, and Pierre Berini, Unidirectional Bragg Gratings Using Parity-Time Symmetry Breaking in Plasmonic Systems, IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 22, NO. 5, 4600712 (SEPTEMBER/OCTOBER 2016). Abstract

l  Choloong Hahn, Youngsun Choi, Jae Woong Yoon, Seok Ho Song, Cha Hwan Oh, and Pierre Berini, Observation of exceptional points in reconfigurable non-Hermitian vector-field holographic lattices, Nature Commun. 7, 12201 (June 2016). Abstract


l  Jae Woong Yoon, Seok Ho Song, and Robert Magnusson, Critical field enhancement of asymptotic optical bound states in the continuum, Scientific Reports, 5, 18301 (December 2015). Abstract

l  Choloong Hahn, Seok Ho Song, Cha Hwan Oh, and Pierre Berini, Plasmonic gain in long-range surface plasmon polariton waveguides bounded symmetrically by dye-doped polymer, Applied Physics Letters 107, 121107 (September 2015). Abstract

l  Myoung Jin Jung, Choloong Han, Jae Woong Yoon, and Seok Ho Song, Temperature and gain tuning of plasmonic coherent perfect absorbers, Opt. Express 23, 19837 (July 2015). Abstract

l  Choloong Hahn, Seok Ho Song, Cha Hwan Oh, and Pierre Berini, Single-Mode Lasers and Parity-Time Symmetry Broken Gratings Based on Active Dielectric-Loaded Long-Range Surface Plasmon Polariton Waveguides, Opt. Express 23, 19922 (July 2015). Abstract

l  Jae Woong Yoon, Myoung Jin Jung, and Seok Ho Song, Gain-assisted critical coupling for high-performance coherent perfect absorbers, Optics Letters 40, 2309 (May 2015). Abstract

l  Kang Hee Seol, Kwang-Geol Lee, and Seok Ho Song, A deep subwavelength cavity formed by total external reflection of surface plasmon polariton, J. of Applied Physics 117, 173104 (May 2015). Abstract

l  Youngsun Choi, Jong-Kyun Hong, Jin-Ho Cho, Kwang-Geol Lee, Jae Woong Yoon, and Seok Ho Song, Parity-time-symmetry breaking in double-slab surface-plasmon-polariton waveguides, Opt. Express 23, 11783 (April 2015). Abstract


l  Jae Woong Yoon, Seok Ho Song, and Robert Magnusson, Ultrahigh-Q metallic nanocavity resonances with externally-amplified intracavity feedback, Scientific Reports, 4, 7124 (Nov. 2014).

l  Kwang-Geol Lee, Ki-Young Choi, and Seok Ho Song, Optimal design of green InGaN/GaN LEDs mediated by surface-plasmon gratings, Current Applied Physics, 14, 1771-1774 (Oct. 2014).

l  Kwang-Geol Lee, Ki-Young Choi, and Seok Ho Song, Experimental observation of a practical limit on enhancement of the spontaneous emission rate in blue GaN-LEDs by mediating surface plasmons, Current Applied Physics, 14, 1639-1642 (Sept. 2014).

l  Dong Joo Choi, Ju Sung Maeng, Key-one Ahn, Myoung Jin Jung, Seok Ho Song, and Young-Ho Kim, Synthesis of Cu or Cu2O-polyimide nanocomposites using Cu powders and their optical properties, Nanotechnology, 25, 375604 (9pp) (Aug. 2014).

l  Kwang-Geol Lee, Ki-Young Choi, Jin-Ha Kim, and Seok Ho Song, Experimental observation of electroluminescence enhancement on green LEDs mediated by surface plasmons, Opt. Express, 22, A1303 (Aug. 2014).

l  Jae Woong Yoon, Jun Hyung Lee, Seok Ho Song, and Robert Magnusson, Unified Theory of Surface-Plasmonic Enhancement and Extinction of Light Transmission through Metallic Nanoslit Arrays, Scientific Reports, 4, 5683 (July 2014).

l  Jun Hyung Lee, Jae Woong Yoon, Myoung Jin Jung, Jong Kyun Hong, Seok Ho Song, and Robert Magnusson, A semiconductor metasurface with multiple functionalities: A polarizing beam splitter with simultaneous focusing ability, Applied Physics Letters 104, 233505 (June 2014).

l  Kilbock Lee, Seok Ho Song, and Jinho Ahn, FDTD simulation of transmittance characteristics of one-dimensional conducting electrodes, Opt. Express, 22, 6269 (March 2014).


l  Jae Woong Yoon, Gang Min Koh, Seok Ho Song, and Robert Magnusson, Measurement and Modeling of a Complete Optical Absorption and Scattering by Coherent Surface Plasmon-Polariton Excitation Using a Silver Thin-Film Grating, Phys. Rev. Lett. 109, 257402 (Dec. 2012).

l  Hojeong Yu, Youngjin Oh, Soowon Kim, Seok Ho Song, and Donghyun Kim, Polarization-extinction-based detection of DNA hybridization in situ using a nanoparticle wire-grid polarizer, Opt. Lett. 37, 3867 (Sept. 2012).

l  Jae Woong Yoon, Myoung Jin Jung, Seok Ho Song, and Robert Magnusson, Analytic Theory of the Resonance Properties of Metallic Nanoslit Arrays, IEEE J. Quantum Electron. 48, 852 (July 2012).

l  H. G. Svavarsson, J. W. Yoon, M. Shokooh-Saremi, S. H. Song, and R. Magnusson, Fabrication and Characterization of Large, Perfectly Periodic Arrays of Metallic Nanocups, Plasmonics, 7, 653 (March 2012).

l  R. Magnusson, H. G. Svavarsson, J. Yoon, M. Shokooh-Saremi, and S. H. Song, Experimental observation of leaky modes and plasmons in a hybrid resonance element, Appl. Phy. Lett. 100, 091106 (Feb. 2012).

l  Kang Hee Seol and Seok Ho Song, (Korean) Characteristics of Nanoscale Modes Guided by the Total External Reflection of Surface Plasmon-Polaritons, Korean J Opt. & Photon. 23, (Feb. 2012).