Title: Chip-scale Photonic Devices for Light-matter Interactions and Quantum Information Processing
Description: Chip-scale photonic devices such as microdisks, photonic crystal cavities and slow-light photonic crystal waveguides possess strong light localization and long photon lifetime, which will significantly enhance the light-matter interactions and can be used to implement new functionalities for both classical and quantum information processing, optical computation and optical communication in integrated nanophotonic circuits. This thesis will focus on three topics about light matter interactions and quantum information processing with chip-scale photonic devices, including 1) Design and characterization of asymmetric resonate cavity with radiation directionality and air-slot photonic crystal cavity with ultrasmall effective mode volume, 2) Exciton-photon interactions between quantum dots and photonic crystal devices and non-classical photon source from a single quantum dot, and 3) Quantum controlled phase gate and phase switching based on quantum dots and photonic crystal waveguide. The first topic is engineered control of radiation directionality and effective mode volume for optical mode in chip-scale silicon micro-/nano-cavities.

High quality factor (Q), subwavelength mode volume (V) and controllable radiation directionality are the major properties for optical cavities designs. In Chapter 2, asymmetric resonant cavities with rational caustics are proposed and interior whispering gallery modes in monolithic silicon mesoscopic microcavities are experimentally demonstrated. These microcavities possess unique robustness of cavity quality factor against roughness Rayleigh scattering. In Chapter 3, air-slot mode-gap photonic crystal cavities with quality factor of 10^4 and effective mode volume ~ 0.02 cubic wavelengths are experimentally demonstrated. The origin of the high Q air-slot cavity mode is the mode-gap effect from the slotted photonic crystal waveguide mode with negative dispersion. The second topic is exciton-photon coupling between quantum dots and twodimensional photonic crystal nanocavities and waveguide localized modes, including Purcell effect in weak coupling regime and vacuum Rabi splitting in strong coupling regime.

In Chapter 4, micro-photoluminescence measurements of PbS quantum dots coupled to air-slot mode-gap photonic crystal cavities with potentially high qualify factor and small effective mode volume are presented. Purcell factor due to ultrahigh Q/V ratios are critical for applications in non-classical photon sources, cavity QED, nonlinear optics and sensing. In Chapter 5, the observation of subpoisson photon statistics from a single InAs quantum dot emission is presented from both continuous wave and pulsed Hanbury Brown and Twiss measurement. Furthermore, strong coupling between single quantum dot exciton line and photonic crystal waveguide localized mode is demonstrated experimentally and theoretically analyzed with master equations, which can be used as a great implementation platform for realizing future solid-state quantum computation. The third topic is quantum controlled phase gate and phase switching operations based on quantum dots and photonic crystal slow-light waveguide. In Chapter 6, we propose a scheme to realize controlled phase gate between two single photons through a single quantum dot embedded in a photonic crystal waveguide.

Enhanced Purcell factor and large β factor lead to high gate fidelity over broadband frequencies compared to cavity-assisted system. The excellent physical integration of this photonic crystal waveguide system provides tremendous potential for large-scale quantum information processing. In Chapter 7, dipole induced transparency can be achieved in a system which consists of two quantum dots properly located in silicon photonic crystal waveguide. Furthermore, we describe how this effect can be useful for designing full Ï€ phase switching in a hetero-photonic crystal waveguide structure just by a small amount of photons.