Prof. Dr. Wenshan CAI

Georgia Tech, School of Electrical and Computer Engineering, Atlanta, Georgia, USA

Dr. Wenshan Cai joined the faculty of the Georgia Institute of Technology in January 2012 as an Associate Professor in Electrical and Computer Engineering, with a joint appointment in Materials Science and Engineering. Prior to this, he was a postdoctoral fellow in the Geballe Laboratory for Advanced Materials at Stanford University. 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 papers in peer-reviewed journals, and the total citations of his recent papers have reached approximately 10,000 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. He 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, all in electrical/electronic engineering. 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). 

Research Interests:

  • Micro- and nanophotonic structures and devices
  • Plasmonics and metamaterials
  • Nonlinear optics and ultrafast phenomena
  • Optoelectronics and integrated photonics
  • Solar energy harvesting
  • Two-dimensional photonic materials

website of Wenshan CaiExternal link

Lecture 1: Manipulation of Light Waves with Optical Metamaterials

Time: March 16, 2018, 14:00
Place: ACP Auditorium, Albert-Einstein-Str. 6, 07745 Jena

Nanostructured metals have provided us with a unique opportunity to manipulate light in an unconventional manner. Collectively, subwavelength metallic structures serve as building blocks for optical metamaterials with properties that were not observed or even speculated about in the past. This is a very exciting frontier in optics and materials science, with the promising goal of yielding better solar cells, faster computer chips, ultrasensitive biochemical detectors, and even invisible devices. In this talk I will provide a general description of metamaterials in the optical regime, include early demonstrations of the first magnetic metamaterial across the entire visible spectrum, the world’s first negative-index material at optical frequencies, and exotic behaviors associated with the wave mixing of light when the nonlinear media possess unconventional material parameters.

Lecture 2: Structured Chirality in Engineered Optical Media

Time: March 20, 2018, 14:00
Place: ACP Auditorium, Albert-Einstein-Str. 6, 07745 Jena

The past few years have witnessed an explosive development of chiral photonic structures that exhibit circular dichroism and optical rotation orders of magnitude larger than conventional materials. Chiroptical responses in such structured media lead to tailored light-matter interactions under circularly polarized incidence, which is further linked to the spin angular momentum of light. While chirality is most commonly applied in linear optical regime, as characterized by the circular dichroism and optical activity, opposing circularly polarized waves can also display parity as a property of higher order optics. In this talk, we present a set of photonic metamaterials that possess pronounced chiroptical features in both the linear and the nonlinear regimes, with applications for chiral-selective spectral resonances, emission control, signal generation, and optical modulation.

Lecture 3: Field- and Carrier-Induced Nonlinear Plasmonics

Time: March 23, 2018, 14:00
Place: ACP Auditorium, Albert-Einstein-Str. 6, 07745 Jena

In this talk we explore active and nonlinear plasmonics by leveraging the field-induced disruption of the inversion symmetry for second-order optical processes, and exploiting the hot-carrier-induced perturbation of the dielectric permittivity for ultrafast all-optical modulation. The enhanced light-mater interaction in plasmonics at a subwavelength regime has enabled varieties of functionalities. Along this venue, the active control of optical properties via external stimuli and the nonlinear conversion of light frequency are among compelling research directions. Here we employ the electrical functionality of nanostructured metals to demonstrate field-induced nonlinear optical processes in various plasmonic systems. Furthermore, we show that the generation of hot carriers via the nonradiative decay of plasmons allows for the sub-picosecond control of light properties in plasmonic systems, in an all-optical fashion.