Ph.D. Candidate: Eric Chatterjee
Research Advisor: Hideo Mabuchi
Date: Friday, May 24, 2019
Location: McCullough 126
Title: Modeling the Optical Response of Monolayer MoS2 in a Cavity
As semiconductor-based systems have approached miniaturization limits due to heat dissipation and signal distribution issues, the focus has shifted to on-chip nanophotonics as a promising replacement. Unlike the traditional architectures, photonic resonators such as optical cavities are controlled by electromagnetic radiation instead of electrical voltage. The key challenge in photonic-based computing lies in replicating the nonlinear input-output relationship characteristic to components such as transistors, since photons do not inherently interact with one another. To this end, one popular solution is to couple the resonator to a saturable absorber. In this talk, I will focus on the prospect of using monolayer MoS2 (a 2D transition metal dichalcogenide) as the saturable absorber, with the material placed inside a Fabry-Perot cavity at low temperature.
When an electron in monolayer MoS2 is optically excited to a higher energy, it interacts electrostatically with the corresponding hole to form an exciton. The strength of the interaction between the excitons and the electromagnetic field is calculated by deriving the electronic band structure of the material and superposing transition dipole moments between valence and conduction band Bloch states. Unlike a multi-atom cavity, the electrostatic interaction between different excitons has a significant effect on the input-output relationship of the cavity. I will show the theoretical model required to calculate the exciton-photon coupling coefficient as well as the exciton-exciton annihilation rate (in addition to other loss rates from the Hilbert space), eventually culminating in the use of a Lindblad-Hamiltonian formalism to derive the optical nonlinearity for the cavity-material system.