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고려대학교 교수소개

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소개

Prof. 최원식 ( Wonshik Choi )

Tel:  02-3290-3118

E-mail: wonshik@korea.ac.kr

http://www.bioimaging.korea.ac.kr

  • About Professor
  • Research
  • Publication
  • Lab Members

  • Profile

    Positions and employment

    2016.07 ~ present     Associate Director, Center for Molecular Spectroscopy and  Dynamics, Institute for Basic Science, Korea

    2017.09 ~ present     Professor, Department of Physics, Korea University, Seoul Korea

    2012.09 ~ 2017.08    Associate Professor, Department of Physics, Korea University, Seoul Korea

    2009.09 ~ 2012.08    Assistant Professor, Department of Physics, Korea University, Seoul Korea

    ​

    Professional activities

    2017.02 ~ present     Editorial Board member, Scientific Reports

    2010.08 ~ 2016.08    Associate Editor for Biomedical Optics Express (published by Optical Society of America)

    2013.03 ~ 2015.02    Executive Editor for Journal of Optical Society of Korea

    ​

    Educational background

    B.S (1997), M.S (1999) and Ph. D. (2004) in Physics, Seoul National University, Korea

    2004 ~ 2005 Postdoctoral associate, Seoul National University, Seoul, Korea 
    2006 ~ 2009 Postdoctoral associate, Massachusetts Institute of Technology, Cambridge, MA 

     

  • Research

    Research background

    Optical imaging has played an essential role in studying various physical, chemical and biological systems by visualizing their structures, dynamics, and functionalities. The research trend for the previous decade is aimed at improving optical resolving power, and significant advances have been made, resulting in an improved spatial resolution that is more than an order of magnitude better than the diffraction limit. This progress has made a tremendous impact on the in vitro studies of single molecules and individual biological cells. However, the use of optical imaging for in vivo applications of interrogating living tissues, which holds promise in the life sciences such as neuroscience and early medical diagnosis, is still in needs of improvements. At the current stage of development, the fundamental limitation is set by the shallow working depth of optical imaging in biological tissues due to the multiple elastic light scattering induced by the tissues.

     

    There have been numerous studies that have attempted to resolve the detrimental effect of multiple light scattering. However, their performance in spatial resolution is compromised with an increase of target depth to such an extent that the ratio of imaging depth to spatial resolution stays around 100 (Figure below). Those approaches that can reach deep inside tend to lose spatial resolution because they rely on the statistical analysis of multiple light scattering, rather than the microscopic details of the scattering events. The approaches covering the other extreme of high spatial resolution tend to be near-sighted because of their inability to tell single- from multiple-scattered waves. With the increase of target depth, the signal strength of single-scattered waves decays exponentially at a length scale set by the scattering mean free path, which is on the order of 100 microns in biological tissues. Conventional high-resolution optical imaging modalities were, therefore, unable to cope with the decreasing ratio of single scattering signal to the multiple scattering backgrounds. First-order corrections have been made to the low-order Zernike polynomial in adaptive optics, but the resulting improvement is marginal.

     

     

    Research objective

    The main aim of our lab is to develop super-depth optical methodologies for imaging, sensing, and light manipulation of targets located deep within scattering media. We will develop optical imaging systems that can cover the dimensions of space, momentum, and time of both incidence and scattered waves. With this unprecedented level of detail on the response of the scattering media, we will solve inverse scattering problems at the microscopic level of scattering events, and identify the time-dependent modes of the scattering media. In doing so, we will achieve super-depth imaging at the microscopic resolution for the elastic and inelastic scattering, and deliver light energy that is two orders of magnitude, or more, larger than currently existing methods. At every step of the process, we will seek to apply these methods to important biological and biomedical applications. 

     

     

    Imaging

    CASS microscopy

    Optical microscopy suffers from a loss of resolving power when imaging targets are embedded in thick scattering media because of the dominance of strong multiple-scattered waves over waves scattered only a single time by the targets. We developed an approach that maintains full optical resolution when imaging deep within scattering media. We use both time-gated detection and spatial input–output correlation to identify those reflected waves that conserve in-plane momentum, which is a property of single-scattered waves. By implementing a superradiance-like collective accumulation of the single scattering (CASS) waves, we enhance the ratio of the single scattering signal to the multiple scattering background by more than three orders of magnitude. An imaging depth of 11.5 times the scattering mean free path is achieved with a near-diffraction-limited resolution of 1.5 μm. Our method of distinguishing single- from multiple-scattered waves will open new routes to deep-tissue imaging and studying the physics of the interaction of light with complex media.

     

    Experimental schematic diagram of the CASS microscope.

    SLD, diode laser; OL, objective lens; BS1, BS2 and BS3, beamsplitters; SLM, spatial light modulator (working in reflection mode, but indicated here as a transmission mode for simplicity); DG, diffraction grating (an aperture was used to select the first-order diffracted wave); SM, path length scanning mirror; CCD, charge-coupled device camera. For clarity, red, green and dark gold are used to indicate incident, reflected and reference waves, respectively, although their wavelengths are the same.

     

    Reference: 

    1. Sungsam Kang, Seungwon Jeong, et al., "Imaging deep within a scattering medium using collective accumulation of single-scattered waves," Nature Photonics, 9 253-258 (9 Mar 2015)

     

    CLASS microscopy

    Thick biological tissues give rise to not only the multiple scattering of incoming light waves, but   also   the   aberrations   of   remaining   signal   waves.   The   challenge   for   existing   optical microscopy   methods   to   overcome   both   problems   simultaneously has   limited   sub-micron spatial resolution imaging to shallow depths. Here we present an optical coherence imaging method that can identify aberrations of waves incident to and reflected from the samples separately, and eliminate such aberrations even in the presence of multiple light scattering. The proposed method records the time-gated complex-feld maps of backscattered waves over various illumination channels, and performs a closed-loop optimization of signal waves for both forward and phase-conjugation processes. We demonstrated the enhancement of the Strehl ratio by more than 500 times, an order of magnitude or more improvement over conventional adaptive optics, and achieved a spatial resolution of 600 nm up to an imaging depth of seven scattering mean free paths.

     

    Screen Shot 2018-08-31 at 10.23.55 AM.pn

    - Angle-dependent phase retardation of single-scattered waves give rise to the image distortion and reduction in signal to noise ratio

    - Input and Output aberrations are hard to distinguish in the case of elastic scattering

     

    Screen Shot 2018-08-31 at 10.28.07 AM.pn

     

    References: 

    1. S. Kang et al., High-resolution adaptive optical imaging within thick scattering media using closed-loop accumulation of single scattering, Nature Communication 8, 2157 (2017)
    2. C. Choi et al., Optical imaging featuring both long working distance and high spatial resolution by correcting the aberration of a large aperture lens, Scientific Reports 8, 9165 (2018)

     

    Lensless and scanner-free endomicroscope

    Recent trends in developing endoscopes is to gain the microscopic resolution and to reduce the diameter of the probes below a millimeter or so. The so-called endomicroscopes satisfying these two requirements provide a minimally invasive way of investigating the fine details of the microenvironments within the target organs. Typically, graded-index (GRIN) lens or image fiber bundles are widely used as imaging probes. In our studies, we used multimode fibers as imaging probes for further reducing the diameter of the unit. Since multimode fibers distort image information due to mode dispersion, bending and twist, we measured the transmission matrix of the fiber to recover the original image. In fact, our method enables us to use any light guiding media as an endoscopic probe. The examples of our investigation are given below.

     

    Schematic layout of single-fiber microendoscope.

     

    Examples of endoscopic imaging of rat villi.

    (a) Conventional transmission imaging. (b) Endoscopic imaging. (c) Numerical propagation of the image in (b).

     

    References: 

    1. Youngwoon Choi, et al., "Scanner-free and wide-field endoscopic imaging by using a single multimode optical fiber," Physical Review Letters, 109, 203901 (2012)
    2. Changhyeong Yoon, et al., "Experimental measurement of the number of modes for a multimode optical fiber," Optics Letters, 37 4558 (2012)
    3. Donggyu Kim, et al., Toward a miniature endomicroscope: pixelation-free and diffraction-limited imaging through a fiber bundle, Optics Letters 39, 1921 (2014)

     

     

    Optical Physics

    Eigenchannels of scattering medium

    Complex media such as random nanostructures and biological tissues induce multiple wave scattering, which interrupts the propagation of waves and attenuates energy transmission. Even for a highly disordered medium, however, it is possible in principle to enhance the delivery of energy to the far side of the medium. Similar to the resonator modes in linear optical cavities, specific modes called eigenchannels exist in a disordered medium and have extraordinarily high transmission. In our study, we experimentally identify the transmission eigenchannels of any given scattering medium by measuring the transmission matrix, and experimentally coupled light to individual eigenchannels by using wavefront shaping. In our early studies, we showed that an eigenchannel transports 3.99 times more energy than uncontrolled waves. This study will open up new avenues for enhancing light energy delivery to biological tissues for medical purposes and for controlling the lasing threshold in random lasers.

     

    Internal field distribution of transmission eigenchannels.

    We performed finite-difference time-domain method to visualize the field distribution of eigenchannels within the scattering media. From the left, propagation of plane waves, eigenchannels with unity transmittance, and eigenchannels with zero transmittance.

     

    Experimental demonstration of reflection eigenchannels.

    (a), (b) and (c): Intensity maps of experimentally shaped incident waves for the first eigenchannel, 1280th eigenchannel and normally incident plane wave, respectively. They correspond to the highest, lowest, and average reflectance modes, respectively. The H and V polarization components were superposed at the incident plane. (d), (e) and (f): Experimentally recorded intensity maps of reflected waves for the cases of (a), (b) and (c), respectively. (g), (h) and (i): Measured intensity maps of transmitted waves for the case of (a), (b) and (c), respectively. Scale bar, 5 μm. The color bar next to (c) indicates intensity in an arbitrary unit and applies also to (a) and (b). The other two color bars follow the same rule.

     

    References: 

    1. Preferential coupling of an incident wave to reflection eigenchannels of disordered media, Wonjun Choi, Moonseok Kim, Donggyu Kim, Changhyeong Yoon, Christopher Fang-Yen, Q-Han Park, and Wonshik Choi, Scientific Reports 5:11393 (2015)
    2. Exploring anti-reflection modes in disordered media, Moonseok Kim, Wonjun Choi, Changhyeong Yoon, Guang Hoon Kim, Seung-hyun Kim, Gi-Ra Yi, Q-Han Park, and Wonshik Choi, Optics Express 23, 12740 (2015) 
    3. The transmission matrix of a scattering medium and its applications in biophotonics, Moonseok Kim, Wonjun Choi, Youngwoon Choi, Changhyeong Yoon, and Wonshik Choi, Optics Express 23, 12648 (2015)
    4. Measurement of the time-resolved reflection matrix for enhancing light energy delivery into a scattering medium, Youngwoon Choi, Timothy R. Hillman, Wonjun Choi, Niyom Lue, Ramachandra R. Dasari, Peter T. C. So, Wonshik Choi, and Zahid Yaqoob, Physical Review Letters 111, 243901 (2013)
    5. Maximal energy transport through disordered media with the implementation of transmission eigenchannels, Moonseok Kim, Youngwoon Choi, Changhyeong Yoon, Wonjun Choi, Jaisoon Kim, Q-Han Park and Wonshik Choi, Nature Photonics 6, 581 (2012)
    6. Transmission eigenchannels in a disordered medium, Wonjun Choi, Allard P. Mosk, Q-Han Park and Wonshik Choi, Physical Review B 83, 134207 (2011)

  • Publication

    [2018]

    1. Selective pump focusing on individual laser modes in microcavities, Jae-Hyuck Choi, Sehwan Chang, Kyoung-Ho Kim, Wonjun Choi, Soon-Jae Lee, Jung Min Lee, Min-Soo Hwang, Jungkil Kim, Seungwon Jeong, Min-Kyo Seo, Wonshik Choi and Hong-Gyu Park, ACS Photonics 5, 2791 (2018)

    2. Senescent tumor cells building three-dimensional tumor clusters, Hyun-Gyu Lee, June Kim, Woong Sun, Sung-Gil Chi, Wonshik Choi and Kyoung J Lee, Scientific Reports 8, 10503 (2018)

    3. Optical imaging featuring both long working distance and high spatial resolution by correcting the aberration of a large aperture lens, Changsoon Choi, Kyung-Deok Song, Sungsam Kang, Jin-Sung Park and Wonshik Choi, Scientific Reports 8, 9165 (2018)

    4. Focusing of light energy inside a scattering medium by controlling the time-gated multiple light scattering, Seungwon Jung, Ye-Ryoung Lee, Wonjun Choi, Sungsam Kang, Jin Hee Hong, Jin-Sung Park, Yong-Sik Lim, Hong-Gyu Park and Wonshik Choi, Nature Photonics 12, 277-283 (2018)

    5. Anderson light localization in biological nanostructures of native silk, Seung Ho Choi, Seong-Wan Kim, Zahyun Ku, Michelle A. Visbal-Onufrak, Seong-Ryul Kim, Kwang-Ho Choi, Hakseok Ko, Wonshik Choi, Augustine M. Urbas, Tae-Won Goo and Young L. Kim, Nature Communications 9, 452 (2018)

     

    [2017]

    1. High-resolution adaptive optical imaging within thick scattering media using closed-loop accumulation of single scattering, Sungsam Kang, Pilsung Kang, Seungwon Jeong, Yongwoo Kwon, Taeseok D. Yang, Jin Hee Hong, Moonseok Kim, Kyung-Deok Song, Jin Hyoung Park, Jun Ho Lee, Myoung Joon Kim, Ki Hean Kim and Wonshik Choi, Nature Communications 8, 2157 (2017)

    2. Three-dimensional imaging of macroscopic objects hidden behind scattering media using time-gated aperture synthesis, Sungsoo Woo, Munkyu Kang, Changhyeong Yoon, Taseok Daniel Yang, Youngwoon Choi and Wonshik Choi, Optics Express 25, 32722 (2017)

    3. Maximizing energy coupling to complex plasmonic devices by injecting light into eigenchannels, Yonghyeon Jo, Wonjun Choi, Eunsung Seo, Junmo Ahn, Q-Han Park, Young Min Jhon and Wonshik Choi, Scientific Reports 7,9779 (2017)

    4. Removal of back-reflection noise at ultrathin imaging probes by the single-core illumination and wide-field detection, Changhyeong Yoon, Munkyu Kang, Jin H. Hong, Taeseok D. Yang, Jingchao Xing, Hongki Yoo, YoungwoonChoi and WonshikChoi, Scientific Reports 7, 6524 (2017)​

    5. Control of randomly scattered surface plasmon polaritons for multiple-input and multiple-output plasmonic switching devices, Wonjun Choi, Yonghyeon Jo, Joonmo Ahn, Eunsung Seo, Q-Han Park, Young Min Jhon and Wonshik Choi, Nature Communications 8:14636 (2017)

     

    [2016]​

    1. Epithelial-to-mesenchymal transition leads to loss of EpCAM and different physical properties in circulating tumor cells from metastatic breast cancer, Kyung-A Hyun, Ki-Bang Goo, Hyunju Han, Joohyuk Sohn, Wonshik Choi, Seung-Il Kim, Hyo-Il Jung and You-Sun Kim, Oncotarget 7, 24677 (2016)

    2. Depth-selective imaging of macroscopic objects hidden behind a scattering layer using low-coherence and wide-field interferometry, Sungsoo Woo, Sungsam Kang, Changhyeong Yoon, Hakseok Ko and Wonshik Choi, Optics Communications 372, 210-214 (2016)

    ​

    [2015]

    1. Hwanchol Jang, Changhyeong Yoon, Euiheon Chung, Wonshik Choi and Heung-No Lee, "Holistic random encoding for imaging through multimode fibers," Optics express 23 6705-6721 (3 Mar 2015)

    2. Sungsam Kang, Seungwon Jeong, Wonjun Choi, Hakseok Ko, Taeseok D. Yang, Jang Ho Joo, Jae-Seung Lee, Yong-Sik Lim, Q-Han Park and Wonshik Choi, "Imaging deep within a scattering medium using collective accumulation of single-scattered waves," Nature Photonics 9 253-258 (9 Mar 2015)

    3. Moonseok Kim, Wonjun Choi, Youngwoon Choi, Changhyeong Yoon and Wonshik Choi, "Transmission matrix of a scattering medium and its applications in biophotonics," Optics express 23, 12648-12668 (6 May 2015)

    4. Moonseok Kim, Wonjun Choi, Changhyeong Yoon, Guang Hoon Kim, Seunghyun Kim, Gi-Ra Yi, Q-Han Park and Wonshik Choi, "Exploring anti-reflection modes in disordered media," Optics express 23, 12740-12749 (6 May 2015)

    5. Wonjun Choi, Moonseok Kim, Donggyu Kim, Changhyeong Yoon, Christopher Fang-Yen, Q-Han Park and Wonshik Choi, "Preferential coupling of an incident wave to reflection eigenchannels of disordered media," Scientific Reports 5, 11393 (16 June 2015)

     

    [2014]

    1. Youngwoon Choi, Changhyeong Yoon, Moonseok Kim, Wonjun Choi and Wonshik Choi, "Optical Imaging With the Use of a Scattering Lens," IEEE Journal of Selected Topics in Quantum Electronics 20, 61 (Mar-Apr, 2014)

    2. Donggyu Kim, Jungho Moon, Moonseok Kim, Taeseok Daniel Yang, Jaisoon Kim, Euiheon Chung and Wonshik Choi, "Toward a miniature endomicroscope: pixelation-free and diffraction-limited imaging through a fiber bundle," Optics Letters 39, 1921 (Apr, 2014)

    3. Yongjin Sung, Niyom Lue, Bashar Hamza, Joseph Martel, Daniel Irimia, Ramachandra R. Dasari, Wonshik Choi, Zahid Yaqoob and Peter So, "Three-Dimensional Holographic Refractive-Index Measurement of Continuously Flowing Cells in a Microfluidic Channel," Physical Review Applied, 1 014002 (Feb, 2014)

    4. Donggyu Kim, Wonjun Choi, Moonseok Kim, Jungho Moon, Keumyoung Seo, Sanghyunu and Wonshik Choi, "Implementing transmission eigenchannels of disordered media by a binary-control digital micromirror device," Optics  Communications, 330 35-39 (May 2014)

    5. Yeon Jeong Kim, Gi-Bang Koo, June-Young Lee, Hui-Sung Moon, Dong-Gun Kim, Da-Gyum Lee, Ju-Yeon Lee, Jin Ho Oh, Jong-Myeon Park, Minseok S. Kim, Hyun Goo Woo, Seung-Il Kim, Pilsung Kang, Wonshik Choi, Tae Seok Sim, Woong-Yang Park, Jeong-Gun Lee and You-Sun Kim, "A microchip filter device incorporating slit arrays and 3-D flow for detection of circulating tumor cells using CAV1-EpCAM conjugated microbeads," Biomaterials 35 7501-7510 (June 2014)

    6. Hwanchol Jang, Changhyeong Yoon, Euiheon Chung, Wonshik Choi and Heung-No Lee, "Speckle suppression via sparse representation for wide-field imaging through turbid media," Optics Express, 22 16619-16628 (June 2014)

    7. Eunsung Seo, Joonmo Ahn, Wonjun Choi, Hakjoon Lee, Young Min Jhon, Sanghoon Lee and Wonshik Choi, "Far-field Control of Focusing Plasmonic Waves through Disordered Nanoholes," Optics Letters, 39 5838 (Oct, 2014)

    8. Youngwoon Choi, Poorya Hosseini, Wonshik Choi, Ramachandra R. Dasari, Peter T. C. So and Zahid Yaqoob, "Dynamic Speckle Illumination Wide-field Reflection Phase Microscopy," Optics Letters, 39 6062 (Oct, 2014)

     

    [2013]

    1. Youngwoon Choi, Timothy R. Hillman, Wonjun Choi, Niyom Lue, Ramachandra R. Dasari, Peter T. C. So, Wonshik Choi* and Zahid Yaqoob, "Measurement of the time-resolved reflection matrix for enhancing light energy delivery into a scattering medium," Physical Review Letters, 111 243901 (2013) (*corresponding author)

    2. Yongjin Sung, Amit Tzur, Seungeun Oh, Wonshik Choi, Victor Li, Ramachandra R. Dasari, Zahid Yaqoob and Marc W. Kirschner, "Size homeostasis in adherent cells studied by synthetic phase microscopy," PNAS 110, 16687 (2013)

    3. Moonseok Kim, Wonjun Choi, Changhyeong Yoon, Guang Hoon Kim and Wonshik Choi, "Relation between transmission eigenchannels and single-channel optimizing modes in a disordered medium," Optics Letters, 38 2994 (2013)

    4. Youngwoon Choi, Changhyeong Yoon, Moonseok Kim, Juhee Yang and Wonshik Choi, "Disorder-mediated enhancement of fiber numerical aperture," Optics Letters, 38 2253 (2013)

    5. Donggyu Kim, Keumyoung Seo, Wonjun Choi, Moonseok Kim, UK Kang, Sanghyun Ju and Wonshik Choi, "Detection of evanescent waves using disordered nanowires," Optics Communications, 297 1-6 (2013)

    6. Timothy R. Hillman, Toyohiko Yamauchi, Wonshik Choi, Ramachandra R. Dasari, Michael, S. Feld, Youngkeun Park and Zahid Yaqoob, "Digital optical phase conjugation for delivering two-dimensional images through turbid media," Scientific Reports, 3 1909 (2013)

     

    [2012]

    1. H.-G. Hong, W. Seo, Y. Song, M. Lee, H. Jeong, Y. Shin, W. Choi, R. R. Dasari and K. An, "Spectrum of the Cavity-QED Microlaser: Strong Coupling Effects in the Frequency Pulling at Off Resonance," Physical Review Letters, 109 243601 (2012) 

    2. Taeseok D. Yang, Wonshik Choi, Tai Hyun Yoon, Kyoung Jin Lee, Jae-Seung Lee, Sang Hun Han, Min-Goo Lee, Hong Soon Yim, Kyung Min Choi, Min Woo Park, Kwang-Yoon Jung and Seung-Kuk Baek, "Real-time phase-contrast imaging of photothermal treatment of head and neck squamous cell carcinoma: an in vitro study of macrophages as a vector for the delivery of gold nanoshells, Journal of Biomedical Optics, 17128003 (2012) 

    3. Changhyeong Yoon, Youngwoon Choi, Moonseok Kim, Jungho Moon, Donggyu Kim and Wonshik Choi, "Experimental measurement of the number of modes for a multimode optical fiber," Optics Letters, 37 4558 (2012) Selected as one of the top download papers of the month

    4. Youngwoon Choi, Changhyeong Yoon, Moonseok Kim, Taeseok Daniel Yang, Christopher Fang-Yen, Ramachandra R. Dasari, Kyoung Jin Lee and Wonshik Choi, "Scanner-free and wide-field endoscopic imaging by using a single multimode optical fiber," Physical Review Letters, 109, 203901 (2012) highlighted, and selected as an editor’s suggestion with a view point

    5. Yongjin Sung, Wonshik Choi, Niyom Lue, Ramachandra R. Dasari and Zahid Yagoob, "Stain-free quantification of chromosomes in live cells using regularized tomographic phase microscopy,"" PLOS one, 7 e49502 (2012) 

    6. Wonjun Choi, Q-Han Park and Wonshik Choi, "Perfect transmission through Anderson localized systems mediated by a cluster of localized modes," Optics Express, 20 20721 (2012)

    7. Moonseok Kim, Youngwoon Choi, Changhyeong Yoon, Wonjun Choi, Jaisoon Kim, Q-Han Park and Wonshik Choi, "Maximal energy transport through disordered media with the implementation of transmission eigenchannels," Nature Photonics, 6 581 (2012)

    8. Seungeun Oh, Christopher Fang-Yen, Wonshik Choi, Zahid Yaqoob, Dan Fu, YongKeun Park, Ramachandra R. Dasari and Michael S. Feld, "Label-Free Imaging of Membrane Potential Using Membrane Electromotility," Biophysical Journal, 103 11-18 (2012) 

    9. Maxim Kalashnikov, Wonshik Choi, Martin Hunter, Chugh-Chieh Yu, Ramachandra R. Dasari and Michael S. Feld, "Assessing the contribution of cell body and intracellular organelles to the backward light scattering," Optics Express, 20 816 (2012). (Corresponding author) 

    10. Moonseok Kim, Youngwoon Choi, Christopher Fang-Yen, Yongjin Sung, Kwanhyung Kim, Ramachandra R. Dasari, Michael S. Feld and Wonshik Choi, "3D differential interference contrast microscopy using synthetic aperture imaging," Journal of Biomedical Optics, 17(2) 026003 (2012)

     

    [2011]

    1. Youngwoon Choi, Moonseok Kim, Changhyeong Yoon, Taeseok Daniel Yang, Kyoung Jin Lee and Wonshik Choi, "Synthetic aperture microscopy for high resolution imaging through a turbid medium" Vol. 36, No. 21 Optics Letters 4263(2011 Nov) ☞ The Best in Imaging Systems from OSA’s Journals

    2. Youngwoon Choi, Taeseok Daniel Yang, Christopher Fang-Yen, Pilsung Kang, Kyoung Jin Lee, Ramachandra R. Dasari, Michael S. Feld and Wonshik Choi, "Overcoming the diffraction limit using multiple light scattering in a highly disordered medium," Physical Review Letters 107, 023902 (2011 July) 

    3. Youngwoon Choi, Taeseok Daniel Yang, Kyoung Jin Lee and Wonshik Choi, "Full-field and single-shot quantitative phase microscopy using dynamic speckle illumination," Optics Letters 36 2465 (2011 July) ☞ The Best in Imaging Systems from OSA’s Journals

    4. Taeseok Daniel Yang, Jin-Sung Park, Youngwoon Choi, Wonshik Choi, Tae-Wook Ko and Kyoung J. Lee, "Zigzag Turning Preference of Freely Crawling Cells," PLoSOne 6 (6) e20255 (2011 June) 

    5. Zahid Yaqoob, Toyohiko Yamauchi, Wonshik Choi, Dan Fu, Ramachandra R. Dasari and Michael S. Feld, "Single-shot Full-field reflection phase microscopy," Optics Express 19 7587 (2011) 

    6. Wonjun Choi, Allard P. Mosk, Q-Han Park and Wonshik Choi, "Transmission eigenchannels in a disordered medium," Physical Review B 83, 134207 (2011) (Corresponding author) 

    7. Moonseok Kim, Youngwoon Choi, Christopher Fang-Yen, Yongjin Sung, Ramachandra R. Dasari, Michael S. Feld and Wonshik Choi, "High-speed synthetic aperture microscopy for live cell imaging," Optics Letters 36 148 (2011) (Corresponding author) 

    8. Christopher Fang-Yen, Wonshik Choi, Yongjin Sung, Charles J. Holbrow, Ramachandra R. Dasari and Michael Feld, "Video-rate tomographic phase microscopy," Journal of Biomedical Optics, 16 011005 (2011) (Corresponding author)

     

    [2010]

    1. Dan Fu, Wonshik Choi, Yongjin Sung, Zahid Yaqoob, Ramachandra R. Dasari and Michael Feld, "Quantitative dispersion microscopy," Biomedical Optics Express, 1 347 (2010) 

    2. Wontaek Seo, Hyun-Gue Hong, Moonjoo Lee, Younghoon Song, Young-Tak Chough, Wonshik Choi, C. Fang-Yen, R. R. Dasari, M. S. Feld, Jai-Hyung Lee, and Kyungwon An, "Realization of a bipolar atomic Solc filter in the cavity-QED microlaser," Physical Review A, 81 053824 (2010) 

    3. Dan Fu, Seungeun Oh, Wonshik Choi, Toyohiko Yamauchi, August Dorn, Zahid Yaqoob, Ramachandra R. Dasari and Michael S. Feld, "Quantitative DIC microscopy using an off-axis self-interference approach," Optics Letters, 35 2370 (2010) 

    4. Yongkeun Park, Monica Diez-Silva, Dan Fu, Gabriel Popescu, Wonshik Choi, Ishan Barman, Subra Suresh and Michael S. Feld, "Static and dynamic light scattering of healthy and malaria-parasite invaded red blood cells," JBO Letters, 15 020506 (2010)

     

    [2009]

    1. Dan Fu, Wonshik Choi, Yongjin Sung, Seungeun Oh, Zahid Yaqoob, Yongkeun Park, Ramachandra R. Dasari and Michael S. Feld, "Ultraviolet refractometry using field-based light scattering spectroscopy," Optics Express, in press (2009)(Corresponding author, KU) 

    2. Maxim Kalashnikov, Wonshik Choi, Chung-Chieh Yu, Yongjin Sung, Ramachandra R. Dasari, Kamran Badizadegan and Michael S. Feld, "Assessing light scattering of intracellular organelles in single intact living cells," Optics Express, in press (2009) (Corresponding author, KU) 

    3. Niyom Lue, Wonshik Choi, Gabriel Popescu, Zahid Yaqoob, Kamran Badizadegan, Ramachandra R. Dasari and Michael S. Feld, "Live cell refractometry using Hilbert phase microscopy and confocal reflectance microscopy," Journal of physical chemistry A, in press (2009) (Corresponding author, KU) 

    4. Boris Khaykovicha, Natalia Kozlova, Wonshik Choi, Aleksey Lomakin, Chintan Hossain, Yongjin Sung, Ramachandra R. Dasari, Michael S. Feld and George B. Benedek, "Thickness-radius relationship and spring constants of cholesterol helical ribbons," PNAS  106 15663 (2009) (KU) 

    5. Yongkeun Park, Wonshik Choi, Zahid Yaqoob, Ramachandra R. Dasari, Kamran Badizadegan and Michael S. Feld, "Speckle-field digital holographic microscopy," Optics Express 17 12285 (2009 July 20) (Corresponding author, KU) 

    6. Zahid Yaqoob, Wonshik Choi, Seungeun Oh, Niyom Lue, Yongkeun Park, Christopher Fang-Yen, Ramachandra R. Dasari, Kamran Badizadegan and Michael S. Feld, "Improved phase sensitivity in spectral domain phase microscopy using line-field illumination and self phase-referencing," Optics Express 17 10681 (2009 June 22) (Corresponding author, KU) 

    7. Hyng-Gue Hong, Wontaek Seo, Moonjoo Lee, Younghoon Song, Wonshik Choi, Christopher Fang-Yen, Ramachandra R. Dasari, Michael S. Feld, Jai-Hyung Lee and Kyungwon An, "Effects of coupled bichromatic atom-cavity interaction in the cavity-QED microlaser," Physics Review A 79, 033816 (2009) 

    8. Yongjin Sung, Wonshik Choi, Christopher Fang-Yen, Kamran Badizadegan, Ramachandra R. Dasari and Michael S. Feld, " Optical diffraction tomography for high resolution live cell imaging," Optics Express 17 266 (2009) (Corresponding author)

     

    [2008]

    1. Niyom Lue, Wonshik Choi, Gabriel Popescu, Kamran Badizadegan, Ramachandra R. Dasari and Michael S. Feld, " Synthetic aperture tomographic phase microscopy for 3D imaging of live cells in translational motion," Optics Express 16 16240 (2008) (Corresponding author) 

    2. Yongkeun Park, Monica Diez-Silva, Gabriel Popescu, George Lykorafitis, Wonshik Choi, Michael S. Feld and Subra Suresh, "Refractive index maps and membrane dynamics of human red blood cells parasitized by Plasmodium falciparum," Proceedings of the National Academy of Sciences of the United States of America 105, 13730 (2008) 

    3. Niyom Lue, Wonshik Choi, Kamran Badizadegan, Ramachandra R. Dasari, Michael S. Feld and Gabriel Popescu, "Confocal diffraction phase microscopy of live cells," Optics Letters 33, 2074 (2008) 

    4. G. Popescu, Y. Park, W. Choi, R. Dasari, M. Feld and K. Badizadegan, "Imaging red blood cell dynamics by quantitative phase microscopy," Blood Cells, Molecules and Diseases 41, 10 (2008) 

    5. Wonshik Choi, Chung-Chieh Yu, Christopher Fang-Yen, Kamran Badizadegan, Ramachandra R. Dasari and Michael S. Feld, "Field-based angle-resolved light scattering study of single live cells," Optics Letters 33, 1596 (2008) 

    6. Wonshik Choi, Christopher Fang-Yen, Kamran Badizadegan, Ramachandra R. Dasari and Michael S. Feld, "Extended depth of focus in tomographic phase microscopy using a propagation algorithm," Optics Letters 33, 171 (2008)

     

    [2007]

    1. "Tomographic phase microscopy," Physics today 60, 26 (2007) 

    2. Wonshik Choi, Christopher Fang-Yen, Kamran Badizadegan, Seungeun Oh, Niyom Lue, Ramachandra R. Dasari and Michael S. Feld, "Tomography phase microscopy," Nature Methods 4 717 (2007). 

    3. Christopher Fang-Yen, Seungeun Oh, Yongkeun Park, and Wonshik Choi, Sen Song and H. Sebastian Seung, Ramachandra R. Dasari and Michael S. Feld, "Imaging voltage-dependent cell motions with heterodyne Mach-Zehnder phase microscopy," Optics Letters 32, 1572 (June 2007). 

    4. Niyom Lue, Wonshik Choi, Gabriel Popescu, Takahiro Ikeda, Ramachandra R. Dasari, Kamran Badizadegan and Michael S. Feld, "Quantitative phase imaging of live cells using fast Fourier phase microscopy," Applied Optics 46, 1836-1842 (April 2007)

     

    [2006]

    1. Hyun-Gue Hong, Wontaek Seo, Moonjoo Lee, Wonshik Choi, Jai-Hyung Lee and Kyungwon An, "Spectral line-shape measurement of an extremely weak amplitude-fluctuating light source by photon-counting-based second-order correlation spectroscopy," Optics Letters 31, 3182 (November 2006) 

    2. Christopher Fang-Yen, Chung-Chieh Yu, Sangkeun Ha, Wonshik Choi, Kyungwon An, Ramachandra R. Dasari and Michael S. Feld, "Observation of multiple thresholds in the many-atom cavity QED microlaser," Physical Review A 73, 042002 (April 2006) 

    3. Wonshik Choi, Jai-Hyung Lee, Kyungwon An, C. Fang-Yen, R. R. Dasari and M. S. Feld, "Observation of sub-Poisson Photon Statistics in the Cavity-QED Microlaser," Physical Review Letters 96, 093603 (March 2006)

     

    [2005]

    1. Wonshik Choi, Moonjoo Lee, Ye-Ryoung Lee, Changsoon Park, Jai-Hyung Lee, and Kyungwon An, C. Fang-Yen, R. R. Dasari and M. S. Feld, "Calibration of Second-order correlation functions for nonstationary sources with a multistart, multistop time-to-digital converter," Review of Scientific Instruments 76, 083109 (July 2005)

     

    [2004]

    1. Myoung-Kyu Oh, Wonshik Choi, Jin-Ho Jeon, Moonjoo Lee, Youngwoon Choi, Sangbum Park, Jai-Hyung Lee and Kyungwon An, "Measurement of hyperfine structures and isotope shifts in 4f 55d6s2 and 4f 66s6p of Sm I," Spectrochimica Acta Part B 59, 1919- 1926 ( September 2004). 

    2. Jin-Ho Jeon, Wonshik Choi, Myoung-Kyu Oh, Kyungwon An, Jai-Hyung Lee, "Generation of optical vortices using light-induced phase mask in a V-type system," Optics Communications 242, 199-207 (August 2004).

     

    [2002]

    1. Won-Kyu Lee, Myoung-Kyu Oh, Won-Shik Choi, Jin-Ho Jeon, Jai-Hyung Lee and Joon-Sung Chang, "Self-Induced Transparency in Samarium Atomic Vapor under Condition of High Temperature and High Density," Jpn. J. Appl. Phys 41, pp. 5170-5176 (April 2002).

     

  • Lab Members

    Research fellows

    Moonseok Kim

    Wonjun Choi

    Junmo Ahn

    Seokchan Yun

    Ye-Ryoung Lee

    Kyung-Deok Song

    Mooseok Jang

    Jin Hee Hong

     

    Graduate students

    Eunsung Seo

    Changhyeong Yoon

    Sungsoo Woo

    Seungwon Jeong

    Hakseok Ko

    Hojun Lee

    Jungho Moon

    Pilsung Kang

    Changsoon Choi

    Yonghyeon Jo

    Yongwoo Kwon

    Munkyu Kang

    Dong-Young Kim