Mid-infrared electro-optic modulation using the Kerr effect for silicon quantum photonics

Abstract

Silicon photonic quantum information processing requires a fast switching capability to actively perform multiplexing (MUX) in large-scale integrated optical circuits that aim to demonstrate linear-optical quantum computing. Operating in the mid-infrared (MIR) at wavelengths beyond 2 µm offers the advantage of lower two-photon loss while maintaining the Kerr nonlinearity in silicon photonics. Modulators using the electro-optic Kerr effect provide a switching mechanism
for manipulating light that takes advantage of these improved nonlinear optical qualities.

This thesis unveils the first working tests of such modulators in the MIR wavelength range that have novel, wide waveguides for their active regions. Chapter 1 introduces the progress in computation, quantum information and its physical implementation. It also covers the topics of nonlinear optics, modulators and multiplexing. Chapter 2 discusses integrated optical components optimised for the MIR. It then presents an overview of the physical implementations of modulation, which is followed by a theoretical evaluation of their effect on quantum states of light. Chapter 3 covers the experimental infrastructure required to test and characterise integrated optical devices. Chapter 4 focuses on initial nonlinear optical measurements made in silicon devices to quantify the nonlinear refraction and absorption at a wavelength of 2.071
µm. Chapter 5 discusses the design and testing of modulators that use the electro-optic Kerr effect, measures the phase-voltage response of the devices and presents modulation observed at frequencies near 100 MHz using one variant of the devices with wide waveguide widths. Finally, Chapter 6 presents initial steps towards actively performing MUX on MIR photons with these
modulators by demonstrating pulsed modulation patterns using continuous-wave laser light at MIR photon-pair wavelengths. Chapter 7 concludes the thesis with a summary and adds final remarks along with possible routes for future work.

Date of Award	27 Sept 2022
Original language	English
Awarding Institution	University of Bristol
Supervisor	Josh Silverstone (Supervisor) & John G Rarity (Supervisor)