Speaker: Yunshan Jiang
Affiliation: Ph.D. Candidate - UCLA
Abstract: Photonic time-stretch, invented at UCLA, has established world’s fastest real-time spectrometers and cameras with applications in biological cell screening, tomography, microfluidics, velocimetry and vibrometry. Time stretch instruments have led to several scientific breakthroughs including the discoveries of optical rogue waves, relativistic electron bunching in synchrotrons, and first ever observations of the birth of laser mode-locking and internal motion of soliton molecules. In time-stretch imaging, the target’s spatial information is encoded in the spectrum of the ultrafast laser pulses, which is stretched in time and then detected by a single-pixel detector and digitized by a real-time ADC, and processed by a CPU or a dedicated FPGA or GPU. Various methods have been proposed to realize time stretch, including single mode fibers, dispersion compensating fibers, chirped Bragg grating, and chromo-modal dispersion. However, none of those methods provide chirp with a large time-bandwidth product, which limits the time/depth range the pulse can measure.
In this study, we demonstrate a discrete time-stretch method that can generate the giant time-bandwidth product with arbitrary nonlinear chirp for operating wavelength from the visible to the infrared. We show its application in warped-stretch (foveated) imaging and a time-of-flight LIDAR with MHz refresh rate.
Most optical sensing and measurement techniques suffer from the limited dynamic range. In a second and related project, we have proposed the concept of optical dynamic range compression. This powerful technique provides a mean to match the dynamic range of the signal to that of the detector and data converter, leading to improved signal to noise ratio and a wider dynamic range. We outline various methods to implement optical dynamic range compression using nonlinear optics, silicon photonics and saturated amplifications.
Biography: Yunshan is currently a Ph.D. candidate in the department of Electrical and Computer Engineering under the mentorship of Professor Bahram Jalali. She received M.S. degree from UCLA in 2015, and B.S. Degree from Zhejiang University, China in 2013.
Date(s) - Mar 13, 2018
10:00 am - 12:00 pm
E-IV Faraday Room #67-124
420 Westwood Plaza - 6th Flr., Los Angeles CA 90095