Year: 2024
Type: article
Abstract: Single photon sources that can emit entangled photons in a deterministic way are critically needed in realizing photon-based quantum information processing in various areas, such as communication, computing and sensing/metrology. In this thesis, we proposed and developed the following nanophotonic devices that are designed to serve as essential building blocks of chip-scale single photon sources: single-quantum-dot (QD)-based LED; plasmonic chiral coupler; and micro-ring waveguide bandpass filter. In our QD-LED structure, CdSe/ZnS core-shell QDs are placed in window-etched nanochannel areas inside MOS and are electrically pumped by injecting electrons and holes through a vertical junction structure. In generating single photons, we exploit the biexciton/exciton emission cascade occurring inside a QD: entangled photon pairs emit with handedness (i.e., right- or left-circular polarized) and as a superposition state of two mutually exclusive and orthogonal product states. Our fabricated QD-LEDs successfully demonstrate single photon emission at room temperature, as characterized by coincidence measurement using a Hanbury-Brown-Twiss measurement setup. We also designed high-performance plasmonic chiral coupler structure for use with the QD-LEDs. First, we modeled a QD emitter as a circularly-polarized (CP) dipole and analyzed the electrodynamics occurring in the near-field regime. CP-dipole near-field is found to harbor a large energy flux circling around and possess spin angular momentum. Our chiral coupler is designed such that the curvature-induced angular momentum matches the spin momentum of dipole near-field. As a result of this momentum matching, our chiral coupler demonstrates high polarization selectivity, high throughput extraction, and high Purcell enhancement. We designed hyperbolic metamaterial structure that supports low-loss loosely-bound surface plasmons (SPs). The motivation of this study is to overcome the intrinsic losses of SP waveguides and to enable long range propagation (chip-scale or beyond). We investigated the trade-off relationship between propagation length and lateral confinement of SP fields and designed a hyperbolic metamaterial system such that propagation length can be increased by many orders of magnitude over conventional limits by suppressing the tangential component of electric field in metal layers. We designed and fabricated Si3N4-based photonic waveguide devices (micro-ring bandpass filters and waveguide couplers) on SOI substrate for future integration with QD-LEDs and chiral couplers.
Author: Shi, Yu
Institution: University of Pittsburgh
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6983667805