Dr. Sohn is a physicist in the Nanoscale Imaging Group in the Nanoscale Device Characterization Division of the Physical Measurement Laboratory (PML) at the National Institute of Standards and Technology (NIST). His graduate research was on the development of the optical alignment system for ArF excimer laser step and scan lithography exposure tool. He joined Electronics Telecommunications Research Institute (ETRI) to be involved in the development of the Next Generation DUV Step-And-Scan Lithography Exposure Tool as a postdoctoral associate in 1998 and joined the Next Generation DRAM Photolitho Task Force Team in the Samsung Electronics Semiconductor Laboratory as a senior staff researcher in 2000. He again joined back ETRI for developing Small Form Factor High Capacity Optical Memory System as a senior staff researcher in Electronics Telecommunications Research Institute (ETRI), where he developed a focusing pickup element using blue laser diode for small form factor disk storage for the first time, until joining NIST in 2005.
Dr. Sohn developed the NIST 193 nm Scatterfield Imaging Microscope enabling sophisticated illuminations for nanostructure characterization. Using this unique tool, he is developing DUV microscopy techniques for 3-dimensional phase imaging and characterization of nanoscale dimensions. He is interested in tackling the fundamental resolution limit in reflection microscopy. His interest also is in developing a single photon imaging technique using orbital angular momentum for various quantum metrology applications. Currently he is leading the development of the photonic quantum state imaging metrology project using high speed gated single photon interference imaging that will elucidate the fundamental quantum phenomena in single molecule and nanoparticle systems. He has authored over 50 journal and proceeding papers and is holding 4 US patents and 3 Korean patents.