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  [이휘돈] Electronically Controlled Dual-Wavelength Switchable SRS Fiber Amplifier in the NIR-II Region for Multispectral Photoacoustic Microscopy - 전기적으로 동작하는 듀얼 파장 스위칭 SRS 광섬유 레이저를 이용한 NIR-II 영역 다분광 광음향 시스템 -

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  2025.04.01

  Laser % Photonics Reviews Oct 2024, 18:2400144 (IF 9.8 JCR 6.3%) Photoacoustic microscopy (PAM) is a high-resolution and non-invasive imaging modality that provides optical absorption contrast. By employing dual- or multiple-wavelength excitation, PAM extends its capabilities to offer valuable spectroscopic information. To achieve efficient multispectral PAM imaging, an essential requirement is a light source characterized by a high repetition rate and switching rate, a ?microjoule pulse energy, and a ?nanosecond pulse duration. However, there exists a notable deficiency in suitable light sources, particularly in the near-infrared-II window. In this study, a custom-built all-fiber-based light source is reported that provides 3 ?J, 2 ns pulses with a repetition rate of 200 kHz. Digitally addressed semiconductor seed lasers, followed by stimulated Raman scattering amplification, enabled arbitrary sequences of pulses having wavelengths of either 1168.4 or 1202.1 nm. In a switching mode of operation, a 100 kHz switching rate is used to alternate between these wavelengths in even/odd pulses. Furthermore, a high-resolution multispectral photoacoustic microscopy of three polymer samples is demonstrated with the proposed light source.
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  [장무석] Meta Shack-Hartmann wavefront sensor with large sampling density and large angular field of view: phase imaging of complex x-x-x-x-x-objects -대형 샘플링 밀도 및 광시야각을 갖춘 메타 Shack-Hartmann wavefront 센서: 복잡한 객체의 위상 이미징-

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  2025.04.01

  Light: Science Applications , (2024)13:187, (IF 20.6, JCR 2.9 %) Shack?Hartmann wavefront sensors measure the local slopes of an incoming wavefront based on the displacement of focal spots created by a lenslet array, serving as key components for adaptive optics for astronomical and biomedical imaging. Traditionally, the challenges in increasing the density and the curvature of the lenslet have limited the use of such wavefront sensors in characterizing slowly varying wavefront structures. Here, we develop a metasurface- enhanced Shack?Hartmann wavefront sensor (meta SHWFS) to break this limit, considering the interplay between the lenslet parameters and the performance of SHWFS. We experimentally validate the meta SHWFS with a sampling density of 5963 per mm2 and a maximum acceptance angle of 8° which outperforms the traditional SFWFS by an order of magnitude. Furthermore, to the best of our knowledge, we demonstrate the ?rst use of a wavefront sensing scheme in single-shot phase imaging of highly complex patterns, including biological tissue patterns. The proposed approach opens up new opportunities in incorporating exceptional light manipulation capabilities of the metasurface platform in complex wavefront characterization.
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  [김정원] Massively parallel electro-optic sampling of space-encoded optical pulses for ultrafast multi-dimensional imaging -공간적으로 인코딩된 광 펄스의 대용량/병렬 전기-광학적 샘플링을 이용한 초고속 다차원 영상 기법-

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  2024.04.22

  Light: Science Applications FEB 2023, (2023)12:44, (IF 19.4, JCR 2.5 %) High-speed and high-resolution imaging of surface profiles is critical for the investigation of various structures and mechanical dynamics of micro- and nano-scale devices. In particular, recent emergence of various nonlinear, transient and complex mechanical dynamics, such as anharmonic vibrations in mechanical resonators, has necessitated real-time surface deformation imaging with higher axial and lateral resolutions, speed, and dynamic range. However, real-time capturing of fast and complex mechanical dynamics has been challenging, and direct time-domain imaging of displacements and mechanical motions has been a missing element in studying full-field structural and dynamic behaviours. Here, by exploiting the electro-optic sampling with a frequency comb, we demonstrate a line-scan time-of-flight (TOF) camera that can simultaneously measure the TOF changes of more than 1000 spatial coordinates with hundreds megapixels/s pixel-rate and sub-nanometre axial resolution over several millimetres field-of-view. This unique combination of performances enables fast and precise imaging of both complex structures and dynamics in three-dimensional devices and mechanical resonators.
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  [김창석] Spatio-spectral 4D coherent ranging using a flutter-wavelength-swept laser -펄럭이는 파장 훑음 레이저를 이용한 공간-스펙트럼 4D 간섭성 거리 계측-

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  2024.04.22

  Nature communications FEB 2024, 1110 (2024), (IF 16.6, JCR 8.2 %) Coherent light detection and ranging (LiDAR), particularly the frequency-modulated continuous-wave LiDAR, is a robust optical imaging technology for measuring long-range distance and velocity in three dimensions (3D). We propose a spatio-spectral coherent LiDAR based on a unique wavelength-swept laser to enable both axial coherent ranging and lateral spatio-spectral beam scanning simultaneously. Instead of the conventional unidirectional wavelength-swept laser, a flutter-wavelength-swept laser (FWSL) successfully decoupled bidirectional wavelength modulation and continuous wavelength sweep, which overcame the measurable distance limited by the sampling process. The decoupled operation in FWSL enabled sequential sampling of flutter-wavelength modulation across its wide spectral bandwidth of 160?nm and, thus, allowed simultaneous distance and velocity measurement over an extended measurable distance. Herein, complete four-dimensional (4D) imaging, combining real-time 3D distance and velocity measurements, was implemented by solid-state beam scanning. An acousto-optic scanner was synchronized to facilitate the other lateral beam scanning, resulting in an optimized solid-state coherent LiDAR system. The proposed spatio-spectral coherent LiDAR system achieved high-resolution coherent ranging over long distances and real-time 4D imaging with a frame rate of 10?Hz, even in challenging environments.
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  [장무석] Deep learning based on parameterized physical forward model for adaptive holographic imaging with unpaired data - 적응 홀로그래픽 영상을 위한 매개변수화 된 물리적 모델 기반 딥러닝-

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  2024.04.22

  Nature Machine Intelligence JAN 2023, 35?45 IF 23.8 (JCR 0.3%) Holographic imaging poses the ill posed inverse mapping problem of retrieving complex amplitude maps from measured diffraction intensity patterns. The existing deep learning methods for holographic imaging often depend solely on the statistical relation between the given data distributions, compromising their reliability in practical imaging configurations where physical perturbations exist in various forms, such as mechanical movement and optical fluctuation. Here, we present a deep learning method based on a parameterized physical forward model that reconstructs both the complex amplitude and the range of x-x-x-objects under highly perturbative configurations where the x-x-x-object-to-sensor distance is set beyond the range of given training data. To prove reliability in practical biomedical applications, we demonstrate holographic imaging of red blood cells flowing in a cluster and diverse types of tissue section presented without any ground truth data. Our results suggest that the proposed approach permits the adaptability of deep learning methods to deterministic perturbations, and therefore extends their applicability to a wide range of inverse problems in imaging.
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  [김창석] Programmable Optical Vernier­Sampled Coherent Ranging - 광학적으로 버니어 샘플링된 프로그래밍 가능한 광결맞음 측정-

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  2023.06.29

  LASER PHOTONICS REVIEWS,June 2023,Volume17, Issue6(IF: 10.947, JCR 5.45%) Extended measurement ranges with coherent ranging necessitate an increase in the digitizer sampling rate. Subsampled coherent ranging can reduce the sampling rate, but it has been demonstrated in a short range below around 10 cm. Herein, programmable optical Vernier-sampled coherent ranging over several tens of meters with a reduced sampling rate using a newly developed stepped-frequency-swept laser (stepped-FSL) is proposed. The measurable range of three-dimensional subsampled coherent ranging can be extended by increasing the coherence length of the stepped-FSL. The proposed stepped-FSL sequentially emits a discrete frequency output by applying a programmable voltage signal to an electro-optic modulator. The free spectral range of the stepped-FSL output can be rapidly and akinetically adjusted by changing the number of steps in the programmable voltage signal. The proposed system realizes an extended measurable range (over 20 m) and a high repetition rate (200 kHz). A low sampling rate of 10 MS s?1 is sufficient for operation at a subsampled interference frequency of 1 MHz. This rate is an order of magnitude lower than that of the conventional coherent ranging using an FSL. Experimental results demonstrate that the programmable optical Vernier-sampled coherent ranging can be improved by leveraging novel optical subsampling with a stepped-FSL.
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  [김정원] Precise Synchronization Between Optical Frequency Comb and a Microwave Signal via EOS-TD - EOS-TD를 통한 광 주파수 빗과 마이크로파 신호원 간의 정밀한 타이밍 동기화 -

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  2023.06.29

  Photonics Research,10(2), 365, Feb 2022 (IF: 7.254, JCR 11.39%) Precise and stable synchronizationbetween an optical frequency comb and a microwave oscillator is important forvarious fields. In this work, we demonstrate the shot-noise-limited performanceof an electro-optic timing detector-based comb-microwave synchronization, whichenabled an unprecedented residual timing noise floor of 53 zs/Hz1/2. We identified that bandpass filteringof the microwave signal and optical pulse repetition-rate multiplication arecritical for achieving this performance.
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  [서민호] Soft, Bioresorbable Cooler for Reversible Conduction Block of Peripheral Nerves - 가역적 말초 신경 신호 조절을 위한 부드럽고 생체 내 분해 가능한 냉각 장치-

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  2023.06.29

  Science,377(6601), 109, Jun 2022 (IF: 63.798, JCR 2.05%) Implantable devices capable of targetedand reversible blocking of peripheral nerve activity may provide alternativesto opioids for treating pain. Local cooling represents an attractive means foron-demand elimination of pain signals, but traditional technologies are limitedby rigid, bulky form factors; imprecise cooling; and requirements forextraction surgeries. Here, we introduce soft, bioresorbable, micro-fluidicdevices thatenable delivery of focused, minimally invasive cooling power at arbitrarydepths in living tissues with real-time temperature feedback control.
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  [정윤찬] Angular Distribution of Luminescence Dissymmetry from a Random Laser upon Chrysina Gloriosa - Chrysina Gloriosa의 외표피에 구축된 무작위 레이저에서 관찰된 발광 비대칭의 각도 분포 -

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  2023.06.29

  Optics Express,29(23), 37712, Nov 2021 (IF: 3.833, JCR 27.23%) Weinvestigate the angular distribution of luminescence dissymmetry of randomlasing in the mixture of rhodamine 6G and titanium dioxide nanoparticles upon abiocompatible natural material substrate. We characterize the light viameasuring the angular distribution of its luminescence dissymmetry factor,which reaches an unusually high maximal value at some specific angle dependingon the handedness of its polarization. This random laser source can be used innumerous potential optoelectronic applications which require light emission ofdistributed luminescence dissymmetry or of high luminescence dissymmetry.
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  [이주한] Microscopic Understanding of Two-Dimensional Transition-Metal Carbides - 2차원 전이금속 탄화물의 예외적 방향에 따른 인장 및 파단 반응의 미시적 이해 -

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  2023.06.29

  Applied Surface Science,585, 152557, May 2022 (IF: 7.392, JCR 2.63%) Forthe first time, we have thoroughly investigated the orientation-dependenttensile mechanical responses of emerging 2D transition-metal carbides, Ti3C2O2 MXenes by using state-of-art reactive MDsimulations. We found that despite its highly bonded multi-atom-thick ceramicstructure, Ti3C2O2 MXene is remarkably stretchable (11-13%) forall direction with isotropic elastic stiffness, which indicated its promisingpotential for wearable and flexible device technologies. In contrast to theisotropic elasticity, the mechanical fracture response of Ti3C2O2 MXene is conspicuously anisotropic, exhibitingan unusual characteristic pattern.