Advancing Ground-Based Instrumentation with Astrophotonics for Stellar Astrophysics and Time-Domain Spectroscopy

This dissertation presents advancements in Astrophotonics with a focus on PolyOculus technology - a novel, scalable approach to astronomical instrumentation designed to enhance observational capabilities in a cost-effective manner. It details the development of the Original PolyOculus Array (OPA), its integrated light-combining device (the photonic lantern), and its dedicated spectrograph, OPASpec. In parallel, the final commissioning of the MIRADAS Near-Infrared spectrograph is described. These instrumental innovations are applied to key astrophysical investigations, including the search for coronal mass ejections on M-dwarfs and time-resolved spectroscopic monitoring of T Coronae Borealis during its pre-eruption phase. By combining cutting-edge instrument design with cross-institutional collaboration, this work contributes to the evolving landscape of ground-based Astrophotonics in support of stellar astrophysics.