报告题目：Manipulation of Nonlinear Optical Processes in Plasmonic Metamaterials
报 告 人：Associate Prof. Wenshan Cai (美国佐治亚理工学院)
Nanostructured metals have offered not only the unprecedented opportunity to generate unconventional electromagnetic properties that are not found in nature, but also the exciting potential to create customized nonlinear media with tailored high-order effects. Two particularly compelling directions of current interests are active nanophotonics, where the optical properties can be purposely manipulated by external stimuli, and nonlinear optics, which enable intensity-dependent frequency conversion of light. By exploring the interaction of these two directions, we leverage the electrical and optical functions simultaneously supported in nanostructured metals and demonstrate electrically-controlled nonlinear processes from plasmonic metamaterials. We show that a variety of nonlinear optical phenomena, including the wave mixing and the optical rectification, can be purposely modulated by applied voltage signals. In addition, electrically-induced and voltage-controlled nonlinear effects facilitate us to demonstrate the backward phase matching in a negative index material, a long standing prediction in nonlinear metamaterials. Other results to be covered in this talk include photon-drag effect in plasmonic structures and ion-assisted nonlinear effects from metamaterials in electrolytes. Our results reveal a grand opportunity to exploit plasmonic metamaterials as self-contained, dynamic electrooptic systems with intrinsically embedded electrical functions and optical nonlinearities.
Wenshan Cai is an Associate Professor in Electrical and Computer Engineering at the Georgia Institute of Technology, with a joint appointment in Materials Science and Engineering. Prior to joining Georgia Tech in 2012, he was a postdoctoral fellow in the Geballe Laboratory for Advanced Materials at Stanford University. Dr. Cai received his B.S. and M.S. degrees from Tsinghua University in 2000 and 2002, respectively, and his Ph.D. from Purdue University in 2008. His scientific research is in the area of nanophotonic materials and devices, in which he has made a major impact on the evolving field of plasmonics and metamaterials. Dr. Cai has published more than 50 journal papers in highly prestigious journals such as Science, Nature Materials, Nature Photonics, Nature Nanotechnology, Nature Communications, etc., and the total citations of his recent papers have reached more than 9,000 within the past 10 years. He authored the book, Optical Metamaterials: Fundamentals and Applications, which is used as a textbook or a major reference at many universities around the world. Dr. Cai is the recipient of several national and international distinctions, including the OSA/SPIE Joseph W. Goodman Book Writing Award (2014), the CooperVision Science & Technology Award (2016), and the Office of Naval Research Young Investigator Award (2017).