Saeidi, Shayan2025-12-192025-12-192025-12-19http://hdl.handle.net/10393/51196https://doi.org/10.20381/ruor-31632This thesis investigates two building-blocks of integrated photonics, hybrid plasmonic semiconductor lasers and waveguide Bragg gratings (WBGs), with the goal of improving tunability, sensing performance, and grating design. The first part examines plasmonic-III-V integration as a platform for tunable lasers aimed at data-center applications, using loss-based mode control to enable wavelength tuning. I also explore the use of hybrid plasmonic semiconductor laser in biosensing and additionally, design an electrically driven LED refractometer as a compact sensing device. The second part of the thesis focuses on WBGs, reviewing weak and strong grating regimes with established simulation techniques. I introduce a new class of gratings, Dirac gratings, whose spectral response remains unchanged with grating order. Finally, I develop an efficient analysis tool based coupled-mode theory for design and optimization of distributed-feedback lasers and reflectors.enAttribution-NonCommercial 4.0 Internationalhttp://creativecommons.org/licenses/by-nc/4.0/Semiconductor LaserPlasmonicsWaveguide Bragg GratingsThesis