Engineered Photonic Structures for Enhanced Light–Matter Interaction and Telecom-Band DFB Lasers

Abstract

High performance photonic devices increasingly rely on resonant micro- and nanoscale structures to shape electromagnetic fields within compact footprints. As two important classes of such resonant devices, this thesis investigates metasurfaces and waveguide Bragg gratings (WBGs) as periodically structured photonic components that enable precise control of light propagation and emission. In the first part, we studied metasurfaces as ultrathin resonant devices that manipulate free space radiation through engineered scattering from sub-wavelength meta-atoms. We employed established numerical and semi-numerical tools to analyze linear and nonlinear responses, including multipolar contributions to the scattering response of linear resonant metamaterials and nonlinear scattering theory for second-harmonic generation (SHG). In the terahertz (THz) regime, we demonstrated an indium antimonide (InSb)-based plasmonic metasurface that supports a spectrally narrow surface lattice resonance (SLR) in a periodic meta-molecule array, and we investigated its potential for sensing and tweezing applications. We further investigated emission engineering in coupled emitter–antenna systems using InSb-based resonant antennae, showing that magnetization and multipolar resonances provide a practical route to dynamically control the spontaneous emission of a quantum emitter. We then focused on nonlinear plasmonic metasurfaces motivated by SHG microscopy applications. We studied a structurally disordered metasurface composed of asymmetrical L- and V-shaped gold meta-atoms and clarified how the SH response is governed by polarization- and orientation-dependent emission channels in the metasurface. To achieve both second-harmonic (SH) signal strength and near-field resolution simultaneously, we proposed a bi-layered stack metasurface design that combines a passive linear metasurface supporting an SLR with an upper nonlinear antenna layer supporting localized surface plasmon resonances (LSPRs), enabling enhanced forward SH emission while maintaining improved near-field resolution. In the second part, we investigated higher-order WBGs as wavelength-selective feedback components for distributed feedback (DFB) semiconductor lasers. We implemented a coupled wave analysis for higher-order gratings with arbitrary profiles and accounted for the effect of radiative waves, which enabled longitudinal mode discrimination for single-mode operation. By extending this analysis into a threshold-oriented framework for modeling lasing onset, we optimized and experimentally characterized a compact third-order surface-etched grating DFB laser on the vertical integration platform, and we demonstrated good agreement between the modeling approach and measured device performance. Overall, this thesis provides practical designs and analysis approaches for THz metasurfaces, THz resonant metamaterials, nonlinear SHG metasurface platforms, and higher-order grating DFB lasers as promising building blocks for sensing, emission control, nonlinear microscopy, and telecom photonic integrated circuits (PICs), respectively.