Sonia Buckley

Engineered quantum dot single-photon sources

Fast, high efficiency and low error single-photon sources are required for the implementation of a number of quantum information processing applications. The fastest triggered single-photon sources to date have been demonstrated using epitaxially grown semiconductor quantum dots (QDs), which can be conveniently integrated with optical microcavities. Recent advances in QD technology, including demonstrations of high temperature and telecommunications wavelength single-photon emission, have made QD single-photon sources more practical. Here we discuss the applications of single-photon sources and their various requirements, before reviewing the progress made on a QD platform in meeting these requirements.

Control of two-dimensional excitonic light emission via photonic crystal

Monolayers of transition metal dichalcogenides (TMDCs) have emerged as new optoelectronic materials in the two dimensional (2D) limit, exhibiting rich spin-valley interplays, tunable excitonic effects, and strong light–matter interactions. An essential yet undeveloped ingredient for many photonic applications is the manipulation of its light emission. Here we demonstrate the control of excitonic light emission from monolayer tungsten diselenide (WSe2) in an integrated photonic structure, achieved by transferring one monolayer onto a photonic crystal (PhC) with a cavity. In addition to the observation of an effectively coupled cavity-mode emission, the suspension effects on PhC not only result in a greatly enhanced (~60 times) photoluminescence but also strongly pattern the emission in the subwavelength spatial scale, contrasting on and off the holes. Such an effect leads to a significant diffraction grating effect, which allows us to redistribute the emitted photons both polarly and azimuthally in the far field through designing PhC structures, as revealed by momentum-resolved microscopy. A 2D optical antenna is thus constructed. Our work suggests a new way of manipulating photons in hybrid 2D photonics, important for future energy efficient optoelectronics and 2D nano-lasers.

Multiply resonant photonic crystal nanocavities for nonlinear frequency conversion

We describe a photonic crystal nanocavity with multiple spatially overlapping resonances that can serve as a platform for nonlinear frequency conversion. We show nonlinear characterization of structures with two resonances nearly degenerate in frequency. We also demonstrate structures with resonances separated by up to 592 nm.

Fast quantum dot single photon source triggered at telecommunications wavelength

We demonstrate a 300 MHz quantum dot single photon source at 900 nm triggered by a telecommunications wavelength laser. The quantum dot is excited by on-chip-generated second harmonic radiation, resonantly enhanced by a photonic nanocavity.

Photonic crystal cavities in cubic (3C) polytype silicon carbide films

We present the design, fabrication, and characterization of high quality factor (Q ~10(3)) and small mode volume (V ~0.75 (λ/n)(3)) planar photonic crystal cavities from cubic (3C) thin films (thickness ~200 nm) of silicon carbide (SiC) grown epitaxially on a silicon substrate. We demonstrate cavity resonances across the telecommunications band, with wavelengths from 1.25 - 1.6 μm. Finally, we discuss possible applications in nonlinear optics, optical interconnects, and quantum information science.

Direct Bandgap Light Emission from Strained Germanium Nanowires Coupled with High-Q Nanophotonic Cavities

A silicon-compatible light source is the final missing piece for completing high-speed, low-power on-chip optical interconnects. In this paper, we present a germanium nanowire light emitter that encompasses all the aspects of potential low-threshold lasers: highly strained germanium gain medium, strain-induced pseudoheterostructure, and high-Q nanophotonic cavity. Our nanowire structure presents greatly enhanced photoluminescence into cavity modes with measured quality factors of up to 2000. By varying the dimensions of the germanium nanowire, we tune the emission wavelength over more than 400 nm with a single lithography step. We find reduced optical loss in optical cavities formed with germanium under high (>2.3%) tensile strain. Our compact, high-strain cavities open up new possibilities for low-threshold germanium-based lasers for on-chip optical interconnects.

Nonclassical higher-order photon correlations with a quantum dot strongly coupled to a photonic-crystal nanocavity

We use the third- and fourth-order autocorrelation functions

Second harmonic generation in photonic crystal cavities in (111)-oriented GaAs

g^{(3)}(\tau_1,\tau_2)

Multiply resonant high quality photonic crystal nanocavities

and

Second-Harmonic Generation in GaAs Photonic Crystal Cavities in (111)B and (001) Crystal Orientations

g^{(4)}(\tau_1,\tau_2, \tau_3)