Hybrid Silicon Photonic Devices for Chem-Bio Sensing and Computing

Date of Award

5-9-2026

Degree Name

Ph.D. in Electro-Optics

Department

Department of Electro-Optics and Photonics

Advisor/Chair

Swapnajit Chakravarty

Abstract

Integrated photonics devices exhibit multiple properties in various aspects including high bandwidth, high switching speed, low power consumption, multiplexing function, etc. Based on the distinctive modulation method of the guided light wave through the silicon waveguide, integrated photonics sensors can be divided into resonance-based sensors and interferometry-based sensors. This dissertation investigates both classes with the goal of achieving ultra-low energy operation, enhanced phase sensitivity, and improved spectral resolution. For resonance-based devices, we demonstrate compact one-dimensional photonic crystal (1D PC) nanocavities with large extinction, high-quality factors, and large free spectral range. Through careful cavity geometry optimization and p-n junction engineering, we presented designs wherein attojoule-per-bit switching energies are potentially achieved. A design approach incorporating phase change materials (PCMs) is proposed, enabling large refractive index modulation to compensate fabrication imperfections and align cavity resonance with the laser source without the need for active power-consuming thermal heaters. For interferometry-based devices, we demonstrate slow-wave-enhanced phase and spectral sensitivity in asymmetric loop-terminated Mach-Zehnder interferometers (LT-MZIs) which significantly improve phase and spectral sensitivity compared with conventional MZIs of identical interferometer arm lengths. The two-dimensional photonic crystal waveguide (2D PCW) LT-MZI is experimentally validated with the limit of detection (LOD) of 3.4×10-4 RIU (refractive index unit) using the bioconjugation of streptavidin and biotin. By considering the various sources of loss in our benchtop fiber-to-fiber photonic integrated circuit measurement system, we showed that it will be possible to reach 10-7 LOD with on-chip integrated light sources and detectors. These results establish slow-light-enhanced LT-MZIs as a scalable platform for ultra-high-sensitivity integrated sensing. Beyond biosensing, we also demonstrated a narrowband Fourier transform spectrometer (FTS) based on spatially heterodyned array of LT-MZI structure to establish the reconstruction of the input light wavelength. The proposed architecture doubles optical phase delay and enhances wavelength resolution compared with conventional MZI designs, addressing the bandwidth-resolution-compactness tradeoff inherent in on-chip FTSs. To compensate for phase errors arising from fabrication imperfections within a narrow wavelength bandwidth in the FTS, the use of PCMs is proposed, enabling zero active power consumption for phase trimming. These results highlight the potential of advanced integrated photonic architectures for high-resolution sensing and spectroscopy in compact on-chip systems.

Keywords

Electromagnetics, Engineering, Optics

Comments

OCLC No. 1591829977

Rights Statement

Copyright 2026, author.

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