Halsall is a senior PSI photonics researcher focusing on semiconductor spectroscopy and photonic quantum device characterization. Research directions: (1) Deep-level transient spectroscopy (DLTS) — characterizing defects and impurities in semiconductor quantum device structures (Si, GaN, SiC) that are relevant to qubit coherence; (2) Photoluminescence mapping — spatial mapping of optical quality in quantum well and dot wafers for quantum sensing device development; (3) InGaN/GaN quantum wells — non-destructive optical characterization of LED and sensor structures; (4) THz and infrared spectroscopy — contactless Hall measurements and Drude response for quantum material characterization. Provides photonic metrology tools for characterizing quantum sensing device materials.

Parkinson's group uses ultrafast optical spectroscopy to study carrier dynamics in photonic materials with quantum device applications. Research directions: (1) Time-resolved photoluminescence — TRPL with single-photon counting to map exciton lifetimes, diffusion, and defect trapping in GaN, perovskite, and 2D semiconductor quantum wells; (2) Optical single-particle spectroscopy — isolating single nanowires or nanocrystals for defect-free measurements of intrinsic optical properties; (3) Photon-number statistics — Hanbury Brown–Twiss measurements of single-photon purity from quantum dots and localized excitons; (4) Semiconductor quantum sensing interfaces — studying how carrier dynamics affect the fidelity of semiconductor-based quantum sensors and emitters.