Nonlinear quantum photonics on graphene/silicons heterostructures

Abstract

Nonlinear optics, a research area that is emerged after the invention of laser in 1960, continues to be widely explored with a broad range of applications from optical communication and spectroscopy to quantum photonics. A long-standing goal is to realize nonlinear optical structures at progressively low optical power down to quantum regime and electrically-tunable, which is difficult given the small nonlinear coefficients of bulk materials. Currently, there arises a new type of 2D nonlinear optical materials with fascinating properties such as broadband saturable absorption and ultrafast carrier dynamics with a large nonlinear refractive index. Graphene with the ease of fabrication, compatibility with CMOS technology and silicon photonics is a strong contender for a new class of optoelectronic and photonic devices and circuits.\n\nIn this talk, I will first review graphene’s relevant physics for its application in nonlinear optics complemented by our theoretical work on the quantum treatment of its nonlinear Kerr coefficient. This includes how the Kerr coefficient can be electrically-tuned for device operation as well as new physics of anomalous optical saturation. I will then present our systematic experimental investigation of measuring Kerr coefficient through optical self modulation effect, with an emphasis on its wavelength dependence and temporal evolution via combined z-scan and pump-probe measurements. Finally, I will present our experimental work on ultrafast optical modulation/switching and bistability in a hybrid graphene-silicon photonic crystal nanocavities providing a world-record of modulation/switching speed and depth with the lowest optical power for an integrated nonlinear silicon-based photonic devices.