Chip-Scale Spectropolarimetric and Quantum Optical Phase Sensing with Semiconductor Nanostructures

When light interacts with materials, they can selectively absorb, reflect, or transmit specific wavelengths and polarizations, and can even change the phase of the light. These interactions, determined by the material's properties and geometry, reveal its composition, structure, and surface characteristics, offering insights into its optical and further quantum photonic properties. However, measuring these light properties typically requires bulky equipment. This work focuses on integrating these measurement capabilities into a compact, chip-scale device for mobile optical sensing. We achieve this with a spectropolarimetric sensor using GaN elliptical nanopillar photodiodes. Precisely tuning the nanopillars' dimensions allows us to control their UV-visible spectrum and polarization-dependent light absorption, enabling simultaneous reconstruction of spectral and polarization information from minimal measurements. Beyond classical sensing, we address quantum optical needs, which require high-precision phase detection of photon qubits. We present a GaAs-based integrated photonic circuit designed to measure the nonlinear optical phase shifts that can arise when two photons interact with a quantum dot. We also propose an optically controllable two-qubit gate based on enhanced Coulomb interactions between two GaN quantum dots, offering a path toward scalable quantum information hardware. This integrated semiconductor approach offers a practical route to advanced spectropolarimetric and quantum optical sensing, paving the way for next-generation photonic systems.