Graphene-Assisted Integrated Nonlinear Optics
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Date
2018-03-09
Authors
Semnani, Behrooz
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
The unique linear and massless band structure of graphene in a purely two-dimensional Dirac fermionic structure has ignited intense research since the first monolayer graphene was isolated in the laboratory. Not only does it offer new inroads into low-dimensional physics; graphene exhibits several peculiar properties that promise to widen the realm of opportunities for integrated optics and photonics. This thesis is an attempt to shed light on the exceptional nonlinear optical properties of graphene and their potential applications in integrated photonics. Following a theoretical exploration of light-graphene interaction, disruptive new insight into the nonlinear optics of graphene was generated. It now appears that graphene can efficiently enable photon-photon interaction in a fully integrated fashion. This property, taken together with ultrawideband tunability and ultrafast carrier dynamics could be fully exploited within integrated photonics for a variety of applications including harmonic generation and all-optical signal processing. The multidisciplinary work described herein combines theoretical modeling and experimentation to proceed one step further toward this goal.
This thesis begins by presenting a semiclassical theory of light-graphene interaction. The emphasis is placed on the nonlinear optical response of graphene from the standpoint of its underlying chiral symmetry. The peculiar energy- momentum dispersion of the quasiparticles in graphene entails a diverging field-induced interband coupling. Following a many-body study of the carrier relaxations dynamics in graphene, it will be shown that the charged carriers in the vicinity of the Dirac point undergo an unconventional saturation effect that can be induced by an arbitrarily weak electromagnetic field. The perturbative treatment of the optical response of graphene is revisited and a theoretical model is developed to estimate the nonlinear optical coefficients including the Kerr coefficient of graphene. The theoretical models are complimented by the experimental results.
The peculiar nonlinear optical properties of graphene together with its ablity to being integrated with optical platforms would render it possible to perform nonlinear optics in graphene integrated nanophotonic structures. Here, the suitability of graphene for nonlinear optical applications is investigated both theoretically and experimentally. The emphasis is placed on an on-chip platform for ultrafast all-optical amplitude modulation. The experimental results indicate strong all-optical modulation in a graphene-cladded planar photonic crystal nanocavity. This development relies heavily on the unique properties of graphene, including its fast carrier dynamics and the special phonon induced relaxation mechanism. Finally, the potential application of graphene based all-optical modulation in time resolved nonlinear spectroscopy is also discussed.
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Keywords
Graphene, Nonlinear Optics, All-Optical Switching