Nonlinear and quantum optics in two-dimensional materials and nanophotonic systems

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Manipulating and exploiting the interaction of light with nanoscopic systems is a central objective of researchers developing a new generation of chips for use in traditional and quantum information systems. In principle, such chips will be faster and use less energy than current electronic chips. A central aim of my work is to develop theoretical and computational models that can be used by researchers to aid in the design of "photonic" chips on which light can be generated, manipulated and detected. Students in my group will be trained in advanced theoretical techniques in optics, solid state physics, quantum information theory and parallel computing. The response of graphene to terahertz electric fields: Graphene is a two-dimensional material (TDM) composed of carbon atoms arranged in a hexagonal lattice. It has attracted considerable scientific and technological attention in recent years in large part due to its unusual electrical properties. It not only has very low resistance, but the resistance can be tuned by applying a voltage perpendicular to the layer and can depend nonlinearly on the field strength. We are developing theoretical and computational models of the interaction of terahertz (1012 Hz) frequency electric fields with graphene and other TMDs, with the aim of developing better models of the high-frequency conductivity of graphene. As part of this, we will be investigating how impurities on the surface of TMDs affect their linear and nonlinear conductivity. We will also be designing waveguide structures to enhance and exploit the nonlinear response of graphene and thereby generate higher frequency sources of terahertz radiation using harmonic generation.Taken as a whole, this work will aid in the development of the next generation of nanophotonic devices, including light modulators, optical switches, and high-frequency sources.    Integrated sources of entangled quantum states of light:  There is currently a worldwide effort to exploit the quantum nature of matter and light to create a new generation of quantum technologies. In particular, quantum states of light show promise for use in quantum cryptography and quantum computing.   Although there are tabletop "bulk" optical systems that can be used to generate many of these states of light, if these states are to be used in practical devices, it is important that we develop nanoscale (~10-9 m) on-chip sources. One of the key difficulties in developing such sources is the scattering losses that arise due to surface roughness and imperfect confinement of light in nanophotonic platforms. The primary focus of this part of my research is to develop and apply theoretical models of the generation and evolution of entangled quantum states of light in integrated nanophotonic systems. These models will play an important role in helping researchers and developers of optical quantum computing systems minimize the detrimental effects of loss on their performance.