Abstract

This thesis presents two independent research works in optical in- terconnects and radio-frequency (RF)-based gaze tracking. The first work demonstrates a silicon optical waveguide fabricated from four through-silicon vias (TSVs) produced using two-photon-absorption- assisted photo-electrochemical etching. Unlike conventional TSV fabrica- tion methods, this approach enables highly localized, non-line-of-sight etching in silicon using a focused femtosecond laser. Four approximately 5 μm diameter TSVs were etched through a 200 μm silicon wafer in a 7 μm by 7 μm pattern, leaving a central silicon region that functions as a waveguide. The fabricated structure achieved an aspect ratio of approxi- mately 40:1 with minimal backside over-etching and relatively consistent hole diameter through the wafer. Modal simulations at 1550 nm showed that the geometry supports guided modes, and optical guiding tests confirmed that light was coupled through the TSV-defined silicon core. The second work presents a smart contact lens system that uses a split-ring resonator (SRR) and 60 GHz RF interrogation for low-power gaze tracking. The resonant response of the SRR changes with incident angle, allowing gaze direction to be estimated from peak frequency measurements rather than image processing. This approach reduces computational complexity, improves tolerance to slowly varying RF power fluctuations, and supports rapid response times for extended reality (XR) applications. Simulation results demonstrate the feasibility of using multiple RF measurements to determine eye pointing direction within a 15 mm contact lens form factor.

Degree

College and Department

Ira A. Fulton College of Engineering; Electrical and Computer Engineering

Rights

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