게시판
최근논문
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[Editor's Pick] Current Optics and Photonics Vol. 9 no. 3 (2025 Jun)_2nd
10 W 15 ns 300 kHz Red-emission of 650 nm Based on Third-harmonic Generation
from Thulium-doped Fiber Laser at 1950 nm
Jinju Kim*, Yong-Ho Cha, Woo-Sang Yu, and Kwang-Hoon Ko
Current Optics and Photonics Vol. 9 No. 3 (2025 June), pp. 202-208
DOI: https://doi.org/10.3807/COPP.2025.9.3.202
Fig. 1 The experimental setup of the 650 nm red laser system includes the following components: Laser diode (LD), isolator (ISO), bandpass filter (BPF), fiber amplifier (FA), electro-optic modulator (EOM), acousto-optic modulator (AOM), circulator, secondharmonic generator (SHG), and third-harmonic generator (THG).
Keywords: Fiber laser, Frequency tripling, PPLN, Thulium laser
OCIS codes: (140.3280) Laser amplifiers; (140.3460) Lasers; (140.3510) Laser, fiber
Abstract
A 10 W, 15 ns, 300 kHz pulsed laser emitting at 650 nm was developed through second- and thirdharmonic generation based on a 20 W pulsed thulium-doped all-fiber laser operating at 1950 nm. The 1950 nm all-fiber laser, which was constructed using a master oscillator power amplifier configuration, comprised one continuous-wave amplifier, two pulsed pre-amplifiers, and a final main amplifier. The amplified output power at the fundamental wavelength was 20 W and it was frequency-tripled to 650 nm using two MgO-doped periodically poled lithium niobate crystals. The maximum emission power achieved at 650 nm was 10 W and the conversion efficiency from 1950 nm to 650 nm was around 50%. To the best of our knowledge, this represents the first development of a nanosecond-pulsed 650 nm emitting source that attains an output power of 10 W through the frequency-tripling of a thulium-doped fiber laser.
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[Editor's Pick] Current Optics and Photonics Vol. 9 no. 3 (2025 Jun)_1st
MEMS Actuators for Tunable Waveguide Devices in Photonic Integrated Circuits: A Brief Review
Dongju Choi, Young Jae Park, Man Jae Her, and Sangyoon Han*
Current Optics and Photonics Vol. 9 No. 3 (2025 June), pp. 185-195
DOI: https://doi.org/10.3807/COPP.2025.9.3.185
Fig. 1 Schematic illustration of microelectromechanical systems (MEMS)-based optical phase shifters using mecha nically movable waveguides: (a) 3D schematic depicting two parallel waveguides (main and perturbing waveguides), where the perturbing waveguide can move either horizontally (inplane actuation) or vertically (out-of-plane actuation). Top of (b) and left-side of (c) are optical mode profiles with distant waveguides for in-plane and vertical configurations. Bottom of (b) and right-side of (c) are optical mode profiles showing significant mode expansion when waveguides are brought closer in both in-plane and vertical directions.
Keywords: Actuator, Microelectromechanical systems, Photonic integrated circuits, Waveguide
OCIS codes: (230.0230) Optical devices; (230.4685) Optical microelectromechanical devices; (230.7370) Waveguides; (250.5300) Photonic integrated circuits;
Abstract
Microelectromechanical systems (MEMS)-based tuning methods offer promising solutions for dynamically controlling optical properties in photonic integrated circuits (PICs) to address the limitations associated with traditional approaches that rely on direct modulation of the material’s refractive index. Conventional methods such as thermo-optic, plasma dispersion, and electro-optic modulation, face significant challenges including high energy consumption, limited refractive index change, and issues with heat dissipation and optical losses. By contrast, MEMS-based actuators directly reposition optical components, enabling reduced device footprints, negligible static power consumption, rapid response times, and improved reliability. This paper systematically explores the operating principles and design characteristics of five representative MEMS actuator technologies widely used in tunable waveguide devices: In-plane comb-drive actuators, cantilever actuators, gap-reducing actuators, vertical digital actuators, and vertical comb-drive actuators. Each actuator type is analyzed for its distinct advantages and challenges, with considerations such as device compactness, switching speed, voltage requirements, and robustness against reliability issues such as pull-in phenomena and stiction. The insights presented emphasize the substantial potential of MEMS-based tuning methods to advance the scalability, energy efficiency, and performance of next-generation PICs. Continued research into improving actuator performance, including increased operation speed, lower operating voltages, and further miniaturization, will be critical to achieving widespread integration and adoption.
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[하이라이트 논문] 한국광학회지 Vol. 36 No. 3 (2025 Jun)
Application of Terahertz Technology Based on Nano Metasurface
나노 메타표면 기반 테라헤르츠 기술 응용
노의영 ㆍ서민아†
한국광학회지 Vol. 36 No. 3 (2025 June), pp. 117-126
DOI: https://doi.org/10.3807/KJOP.25.0002
Fig. 1 Simplified optical setup schematic of the terahertz timedomain spectroscopy (THz-TDS) system.
Keywords: 메타표면, 광학 센서, 광학 물성, 테라헤르츠 분광
OCIS codes: (160.3918) Metamaterials; (160.4760) Optical properties; (280.4788) Optical sensing and sensors; (300.6495) Spectroscopy, terahertz
초록
본 논문에서는 테라헤르츠 시간영역 분광법(terahertz time-domain spectroscopy, THz-TDS)과 이 영역에서 작동하는 나노 메타표면을 소개하고, 이를 활용하여 다양한 소재의 물리적 고유 특성 분석 및 기능성 재료를 활용한 고도화된 테라헤르츠 메타표면 기반 센서 플랫폼에 대한 연구를 소개하고자 한다. 해당 논문에서 다루고 있는 나노슬롯 구조의 메타표면은 전기장을 국소적으로 증폭시킴으로써 기존에 측정하지 못했던 물질의 고유 전자기적 특성을 정밀하게 분석할 수 있다. 이를 바탕으로, 본 논문에서는 세 가지 연구 사례를 소개하고자 한다. 가장 먼저 소개할 논문에서는 페로브스카이트 물질을 나노 메타표면에 결합시켜 포논-포톤(phonon-photon) 강결합 현상을 통한 Rabi splitting 을 유도함으로써, 고유상태(eigenstate) 폴라리톤 모드의 형성을 실험적으로 확인하였다. 이어서 나노 메타표면에 팔라듐을 결합시켜 수소 기체와의 반응 시 관측되는 상변이 및 수분 생성 반응을 THz-TDS를 통해 실시간으로 확인 가능한 고감도 센서를 구현한 연구 사례를 보여준 후, 마지막으로 구리 기반의 나노슬롯 내부에 산화 구리(CuO) 나노플라워를 성장시켜 아세틸콜린과의 화학반응을 통한 센싱 플랫폼을 제시한 논문을 소개하며 마무리하고자 한다. 본 논문에서는 이와 같이 다양한 테라헤르츠 나노 메타표면 기반의 센싱 및 분석 플랫폼에 대한 연구를 소개 함으로써, 기능성 소재와 메타표면 구조와의 결합을 통해 테라헤르츠 대역 내 고감도 센싱 기술의 확장 가능성과 향후 응용 분야에 대한 전망을 제시하고자 한다.
Abstract
In this paper, we present an overview of terahertz time-domain spectroscopy (THz-TDS) and nano-metasurfaces operating in the THz regime. To further explore their application in probing the physical properties of materials and highlight recent advances in THz metasurface-based sensing platforms with the implementation of functional nano-materials, we introduce three representative studies. In the first research paper, the researchers integrated perovskite thin films with a THz nano-slot metasurface to experimentally demonstrate world-recording Rabi splitting (Ω = 0.48w 0 ) induced by phonon-photon ultrastrong coupling. The following study suggested a highly sensitive hydrogen gas sensing platform by employing palladium thin film as a functional material to create 14-nm-wide effective nanogap formation. This approach enabled real-time monitoring of phase transitions and water generation reactions triggered by the intercalation of hydrogen gas into a palladium lattice. Lastly, another sensing platform with high sensitivity toward acetylcholine, based on the chemical reaction between CuO nanoflowers and acetylcholine, was introduced. The CuO nanoflowers were synthesized in the slot structure of the Cu-based metasurface to enhance the chemical reaction via increasing the surface-to-volume ratio. By summarizing the recent advances, this paper highlights the potential of THz nano-metasurface-based platforms for highly sensitive sensing technologies and their future applications across various fields.
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[하이라이트 논문] 한국광학회지 Vol. 36 No. 2 (2025 April)
Wavelength-swept Source-based Wide Line-field Optical Coherence Tomography System
파장가변광원 기반 광폭 선형영역 광결맞음 단층영상 시스템
이승석ㆍ마혜준ㆍ김현성ㆍ최은서†
한국광학회지 Vol. 36 No. 2 (2025 April), pp. 85-93
DOI: https://doi.org/10.3807/KJOP.2025.36.2.085
Fig. 1 Lab-built wavelength-swept light source. The light source comprises two semiconductor optical amplifiers (SOAs), two isolators, a Fabry-Perot (FP) filter,
and an output coupler. SOA2 is employed to amplify the output power emitted from the ring cavity.
Keywords: 대면적, 비주사, 광단층촬영법, 파장가변광원, 광폭 선형영역
OCIS codes: (100.6950) Tomographic image processing; (110.3175) Interferometric imaging; (120.3180) Interferometry
초록
본 논문에서는 전수검사에 활용하기 위해 개발된 line-field optical coherence tomography (LF-OCT) 시스템의 성능을 제시하였다. 광섬유 고리 공진기와 파장가변필터를 이용한 파장가변광원은 중심파장 1330 nm, 파장 반치폭 80 nm, 출력 광세기 90 mW의 특성을 보이며 100 Hz의 반복률로 동작하였다. 총 3장의 렌즈로 구성된 광폭 스캔 렌즈는 폭 100 mm 이하, 200 mm 길이의 선형빔을 발생시킬 수 있었 다. 파장가변광원과 절반 크기로 가공된 광폭 스캔 렌즈를 가지고 마이켈슨 간섭계 형태로 구현된 LF-OCT 시스템은 20 mm의 깊이 분해능과
Abstract
This paper presents the performance of a line-field optical coherence tomography (LF-OCT) system developed for full inspection. A wavelengthswept light source using a fiber ring resonator and a wavelength-tunable filter was operated at a repetition rate of 100 Hz with a center wavelength of 1330 nm, a spectral bandwidth of 80 nm, and an output power of 90 mW. The wide scan lens, designed in three lenses, could generate a line-field beam less than 100 mm wide and 200 mm long. The LF-OCT system implemented in a Michelson interferometer with a wavelength-swept light source and a wide-scan lens fabricated to half its dimension presented an axial resolution of 20 mm and a depth range of 2.84 mm at 3 dB. We could confirm 3 mm imaging depth through gauge block imaging and obtain 100-mm-wide tomographic images of a metal ruler without scanning. By optimizing the implemented LF-OCT, we will be able to demonstrate its utility as an inspection device for real-time, full-scale inspections required in industrial fields.
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[Editor's Pick] Current Optics and Photonics Vol. 9 no. 2 (2025 April)
High-harmonic Generation in van der Waals Two-dimensional Materials
Dasol Kim, Alexis Chacon, and Jonghwan Kim*
Current Optics and Photonics Vol. 9 No. 2 (2025 April), pp. 95-107
DOI: https://doi.org/10.3807/COPP.2025.9.2.95
Fig. 1 Schematics of high-harmonic generation in van der Waals (vdW) 2D materials:
(a) Commonly used vdW 2D materials. (b) Experimental configuration of high-harmonic-generation measurement.
Keywords: High energy photon sources, High harmonic generation, Solid state physics, Strong-field, light-matter interaction, van der Waals 2D materials
OCIS codes: (040.7480) X-rays, soft X-rays, extreme ultraviolet (EUV); (140.0140) Lasers and laser optics; (160.4330) Nonlinear optical materials; (190.0190) Nonlinear optics; (320.0320) Ultrafast optics
Abstract
High-harmonic generation (HHG) in gases has long enabled tabletop access to coherent extreme ultraviolet (XUV) and soft X-ray radiation. More recently HHG has been extended to the solid-state realm, offering potential advantages such as higher conversion efficiency, tunability via band-structure engineering, and integration with photonic devices. Among emerging solid-state platforms, van der Waals (vdW) two-dimensional (2D) materials—e.g., graphene, transition-metal dichalcogenides (TMDs), and black phosphorus—exhibit pronounced quantum confinement, strong excitonic effects, and valleyselective dynamics. These properties yield unique HHG signatures, including polarization dependence, extended harmonic orders, and topological effects. This review summarizes fundamental mechanisms of HHG in vdW 2D materials, key experimental breakthroughs, and state-of-the-art theoretical approaches. We discuss exciton-driven enhancements, Berry-curvature-induced polarization, and device-integration challenges. We also highlight prospective directions, such as advanced ultrafast spectroscopy and applications in attosecond science, underscoring the rich opportunities and persistent challenges in harnessing strong-field light-matter interactions in 2D quantum materials.
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[Editor's Pick] Current Optics and Photonics Vol. 9 no. 1 (2025 February)
Recent Theoretical and Experimental Progress on Boson Sampling
Changhun Oh*
Current Optics and Photonics Vol. 9 No. 1 (2025 Februrary), pp. 1-18
DOI: https://doi.org/10.3807/COPP.2025.9.1.1
Fig. 1 Setup for Fock-state boson sampling. N indistingui shable photons pass through an M-mode interferometer, and then are measured at the output modes on the Fock basis. Reprinted from R. Garcia-Patron et al. Quantum 2019; 3; 169. Copyright © 2019, R. Garcia-Patron et al. [35].
Keywords: Boson sampling, Quantum advantage, Quantum computer, Quantum optics
OCIS codes: (270.0270) Quantum optics; (270.5585) Quantum information and processing; (270.6570) Squeezed states
Abstract
Boson sampling is a restricted model of quantum computation, designed to achieve quantum advantage using nonuniversal quantum systems. By harnessing the quantum interference of indistinguishable bosons (typically photons), it becomes possible to sample from a probability distribution, which is intractable for classical computers. This paper reviews the theoretical foundations of boson sampling and its variations, including Fock-state, scattershot, and Gaussian boson sampling, along with significant experimental progress, from early small-scale demonstrations to large-scale quantum supremacy claims. We further explore classical algorithms for simulating boson sampling, which are crucial for benchmarking the performance of experimental results. Finally we examine potential applications of boson sampling in various fields, including simulation of molecular vibronic spectra in quantum chemistry, and solution of graph-based problems in optimization. These applications demonstrate the wide-ranging impact that boson sampling could have on industries that rely on complex computational models, making it a promising quantum technology for near-term applications.
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[Editor's Pick] Current Optics and Photonics Vol. 8 no. 6 (2024 December)_2nd
Binary-optimization-based Multilayers and Their Practical Applications
Geon-Tae Park, Rira Kang, Byunghong Lee, and Sun-Kyung Kim*
Current Optics and Photonics Vol. 8 No. 6 (2024 December), pp. 545-561
DOI: https://doi.org/10.3807/COPP.2024.8.6.545
Fig. 1 Workflow of binary-optimization-based multilayer design and its applications. (a) Schematic of the iterative optimization cycle, composed of four primary steps [53]. (b) (i) Schematic of antireflective coatings (ARC) applied to a lens, designed to minimize reflectance at the target wavelength λ0 over a wide range of incident angles θ. (ii) Illustration of transparent radiative coolers (TRCs) for energy-saving windows, engineered to reflect ultraviolet and near-infrared light while transmitting visible light, and maintaining high emissivity within the atmospheric window. The red line represents the target transmittance spectrum, and the blue line represents the target emissivity spectrum for an ideal transparent radiative cooler. (iii) Schematic of bandpass filters for thermophotovoltaics (TPVs), designed to enhance the efficiency of the photovoltaic (PV) cell by selective emission. The red dashed line represents the spectral irradiance of a blackbody IBB, and the blue solid line represents the external quantum efficiency (EQE) multiplied by the intensity of blackbody radiation (IBB). The green solid line shows the target spectrum of a selective emitter with unit emissivity.
Keywords: Binary optimization, Machine learning, Multilayer, Optical coating, Optical design
OCIS codes: (200.0200) Optics in computing; (220.0220) Optical design and fabrication; (310.0310) Thin films; (310.1210) Antireflection coatings; (310.6845) Thin film devices and applications
Abstract
Multilayers composed of two or more materials enable the regulation of transmission, reflection, and absorption spectra across one or multiple bands. While analytic formulas based on well-established interference conditions, such as those employed in single-, double-, and triple-layer antireflective coatings and distributed Bragg reflectors, have provided suitable solutions for traditional optical coatings, they are limited in achieving the intricate spectral characteristics required by multifunctional optical coatings. To overcome this limitation, a variety of machine learning-based design algorithms have been rigorously studied. Among these, binary optimization has proven particularly effective for designing multilayer optical coatings. This approach transforms a given multilayer into a binary vector with multiple bits, where each bit represents one of the constituent materials, and quickly identifies an optimal figureof-merit by analyzing the interactions among the elements of the binary vector. In this review article, we elucidate the principles of binary optimization and explore its applications in the design of multilayers for antireflective coatings for high-numerical-aperture lenses, transparent radiative coolers for energysaving windows, and bandpass filters for thermophotovoltaics. Furthermore, we address the limitations, challenges, and perspectives of machine learning-based optical design to guide directions for future research in this field.
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[Editor's Pick] Current Optics and Photonics Vol. 8 no. 6 (2024 December)_1st
A Tutorial on Inverse Design Methods for Metasurfaces
Jin-Young Jeong† , Sabiha Latif† , and Sunae So*
Current Optics and Photonics Vol. 8 No. 6 (2024 December), pp. 531-544
DOI: https://doi.org/10.3807/COPP.2024.8.6.531
Fig. 1 Schematic illustration of an overview of inverse design metasurfaces using machine learning and optimization methods.
Keywords: Inverse design, Machine learning, Metasurface, Optimization algorithm
OCIS codes: (150.1135) Algorithms; (240.0240) Optics at surfaces
Abstract
This paper provides a tutorial on inverse design approaches for metasurfaces with a systematic analysis of the fundamental methodologies and underlying principles for achieving targeted optical properties. Traditionally, metasurfaces have been designed with extensive trial-and-error methods using analytical modeling and numerical simulations. However, as metasurface complexity grows, these conventional techniques become increasingly inefficient in exploring the vast design space. Recently, machine learning and optimization algorithms have emerged as powerful tools for overcoming these challenges and enabling more efficient and accurate inverse design. We begin by introducing the fundamentals of optical simulations used for forward modeling of metasurfaces and their relevance to inverse design. Next, we explore recent advancements in applying machine learning techniques such as neural networks, Markov decision processes, and Monte Carlo simulations, as well as optimization algorithms, including automatic differentiation, the adjoint method, genetic algorithms, and particle swarm optimizations, and show their potential to revolutionize the metasurface design process. Finally, we conclude with a summary of key findings and insights from this review.
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[하이라이트 논문] 한국광학회지 Vol. 35 No.6 (2024 December)
Recent Trends in Bioinspired Camera Systems for Intelligent Robotics
지능형 로봇을 위한 생체모사형 카메라 연구 최신 지견
장진영1ㆍ장세희1ㆍ송영민1,2,3†
한국광학회지 Vol. 35 No.6 (2024 December) pp. 265-375
DOI: https://doi.org/10.3807/KJOP.2024.35.6.265
Fig. 1 (a) Photograph of the tunable hemispherical electronic eye camera system. (b) Photographs of the photodiode array imaged through a lens at different magnifications (left: smaller radius of curvature, right: larger radius of curvature). (c) Image demonstration of a test pattern (left: flat detector, right: detector shape matched to the Petzval surface). (a)–(c) are reprinted from I. Jung et al. Proc. Natl. Acad. Sci. 2011; 108; 1788-1793. Copyright © 2011, National Academy of Sciences [2] . (d) Optical layout showing a monocentric imager designed with a single ball lens. (e) Photographs of the five-gore structure before mounting and curved device positioned in a hemispherical fixture. (d) and (e) are reprinted from T. Wu et al. Microsyst. Nanoeng. 2016; 2; 16019. Copyright © 2016, T. Wu et al. [3] . (f) Photograph of the phototransistor array on a planar substrate. The inset shows an exploded schematic view of a phototransistor structure. (f) is reprinted from C. Choi et al. Nat. Commun. 2017; 8; 1664. Copyright © 2017, C. Choi et al. [6] . (g) Curvature forming method using two axisymmetric models of a spherical wrapping process. (h) Photograph of a curved complementary metal oxide semiconductor (CMOS) image sensor. (g) and (h) are reprinted with permission from Guenter et al. Opt. Express 2017; 25; 13010-13023. Copyright © 2017, Optical Society of America [8].
Keywords: 생체모사형 카메라, 이미지 센서, 비전 시스템
OCIS codes: (040.1490) Cameras; (110.0110) Imaging systems; (220.0220) Optical design and fabrication
초록
지능형 로봇 시대가 도래함에 따라 이미지 센서 또는 카메라 모듈에도 각 수요처에 따른 제품군의 다양화 필요성이 대두되고 있다. 이와 동시에 초소형/저전력 구동부터 하드웨어 레벨 물체 인식까지, 기존 카메라에서 구현하기 어려운 성능에 대한 수요도 늘고 있다. 한편 인간의 눈을 비롯한 자연계 동물의 눈 구조 및 기능의 우수함과 다양성은 미래 비전 시스템 개발에 큰 영감을 준다. 특히 동물의 서식지 및 생활 환경에 적응하기 위해 생태학적으로 진화한 눈에는 기존의 카메라에서 볼 수 없던 기능이 다수 존재하기 때문에, 최근 이를 모방하기 위한 연구가 활발히 이루어지고 있다. 이러한 생체모사형 카메라의 분야는 크게 렌즈 광학계, 이미지 센서, 나노포토닉 구조, 뉴런/시냅스 모사로 나눌 수 있으며, 최근에는 이를 모두 통합하여 하나의 완성된 비전 시스템을 만들기 위한 시도가 이루어지고 있다. 본 리뷰에서는 세부기술별로 나누어 연구 동향을 살피기보다는, 기술의 발전 방향에 따른 생체모사형 카메라 연구의 흐름을 추적하고자 한다.
Abstract
With the advent of the intelligent robotics era, there is an increasing demand for a variety of image sensors and camera modules to meet the needs of various applications. At the same time, demand is growing for performance such as ultra-compact size, low-power operation, and hardware-level object recognition that is difficult to achieve with existing cameras. The superior structures and functionalities of natural eyes, including those of humans and other animals, provide significant inspiration for the development of next-generation artificial vision systems. In particular, the unique characteristics of animal eyes, which have evolved ecologically to adapt to specific habitats and environments, exhibit functionalities beyond those found in conventional cameras. Consequently, research aiming to mimic these natural optical systems has become very active. Bioinspired cameras can generally be categorized into lens optics, image sensors, nanophotonic structures, and neuron/synapse mimics. Recently, there have been attempts to integrate all these components into a complete vision system. This review aims to trace trends in bioinspired cameras, focusing not on the technical aspects of individual components but on overall directions in technological advancement.
