When
July 30, 2026, 11 a.m. – 2 p.m.
Title:
Shared-Gain Multicavity VECSELs: Experiment, Theory, and Modeling Beyond Hartree-Fock
Abstract:
Shared-gain multicavity Vertical External Cavity Surface Emitting Lasers (VECSELs) are developed as compact ultrafast sources and as model systems for nontrivial nonequilibrium semiconductor dynamics. The central goal of this thesis is to generate multiple modelocked pulse trains from a common gain medium while retaining spectral separation, repetition-rate control, and mutual coherence for dual-comb spectroscopy and low-jitter pump-probe measurements.
A dual-V shared-gain VECSEL is demonstrated experimentally. Two independently addressable mode-locked cavities operate from a single resonant periodic-gain chip, with the two arms incident on the gain structure at different angles. This angular separation shifts the preferred operating wavelength of each cavity and reduces direct gain competition. Stable dual-channel operation is obtained with distinct spectra and repetition rates, showing that shared-gain multicavity operation can be used as a practical route toward semiconductor multi-comb sources.
A microscopic model is developed for the shared-gain chip, resolving the carrier populations and polarizations quantum well by quantum well. Gain recovery follows from kinetic hole burning, carrier refilling, and Coulomb-renormalized light-matter coupling rather than from an imposed gain curve. Coupled to nonparaxial beam propagation, the model shows how angular wavelength discrimination, pulse attraction, gain competition, and carrier-mediated coupling control single, dual, and triple V cavity operation.
The carrier dynamics are further extended beyond the Hartree-Fock level through second Born-Markov scattering and polarization-scattering terms. Because the resulting collision integrals are computationally demanding, conservation-law reduction, symbolic factorization, sparse algebraic reorganization, and hardware-oriented execution are used to make the higher-order many-body terms computationally tractable.
Together, the experimental and theoretical results establish a framework for shared-gain multicavity VECSELs and establish a novel path towards VECSEL multi-comb systems and beyond.
Committee:
Dr. Jeromy Moloney (Chair)
Dr. Masud Mansuripur
Dr. Jason Jones
Where
July 30th, 2026, 11:00 AM - 2:00 PM in Meinel Conference Room 821. Please email Simon (tsaoussis@arizona.edu) or graduate student advisor Jini Kandyil (jini@optics.arizona.edu) for the Zoom link.