Title:  Active and Nonlinear Nanophotonics Facilitated by Hot-Carrier Dynamics

Committee:

Dr. Wenshan Cai, ECE, Chair , Advisor

Dr. Ali Adibi, ECE

Dr. Eric Vogel, MSE

Dr. Benjamin Klein, ECE

Dr. Tianquan Lian, Emory

Abstract:  The ever-increasing demand for bandwidth scalability and high-speed operation is the driving force for the discovery of ultrafast switches. As electronics approaches its intrinsic limitations, pursuing new computational paradigms for data processing is inevitable. In recent years, optical computing –replacing electrons with photons– has been introduced as a powerful alternative to boost computational capacities beyond that of solid-state electronics. Up to date, however, the primary role of optical technologies in data processors has been limited to the realization of communication links between electronic blocks, often through the incorporation of optical fibers and, more recently, photonic waveguides. To expand the contribution of optics, it is essential to implement optical switches within CMOS-integrable platforms. This PhD thesis is focused on the exploration of new techniques for the implementation of ultrafast all-optical switches at two equally important levels: (i) material design; and (ii) device design. In the first half of this thesis, we propose and experimentally demonstrate that the semi-instantaneous transport of plasmonic hot electrons in hybrid metal/dielectric systems enables coherent control over the third-order nonlinear properties of noble metals. By relying on the ultrafast dynamic of hot-electron transport, we design prototypical plasmonic structures that facilitate the sub-picosecond all-optical switching of intensity, phase, and polarization of light. In the second half, we further expand the contribution of plasmonic hot carriers in the field of active and nonlinear nanophotonics and propose a fundamentally new paradigm for inducing optical nonlinearities of second-order type in centrosymmetric materials upon the transport of hot electrons. We believe that the collection of proposed and demonstrated ideas in this PhD thesis not only introduces a new methodology for the design of ultrafast optical switches but also opens up a new problem set for physicists at the crossroads of nonlinear optics, hot-carrier physics, and nanophotonics.