PhD Thesis Defenses

Waveguide structures for efficient nonlinear optical conversion and distributed-feedback laser resonators.

Integrated optical devices enable the development of miniaturized componentswith increased functionality, mechanical stability, robustness and reducedcost. Integrated devices that generate, manipulate and detect light enable opticalsystems that could not be implemented otherwise, at the vanguard ofboth technology and fundamental research. Among a multitude of integratedoptical functionalities, nonlinear optical converters and distributed-feedbackresonators are of special relevance. The former is particularly important becauseit enables the generation of coherent radiation in spectral regions inaccessibleby available lasers, while the latter enables single-frequency lasersources. This thesis concerns both functionalities.

This thesis comprises waveguides on rubidium-doped potassium titanylphosphate and lithium niobate, for second-harmonic generation via quasiphasematching. Simulations and a literature review provide a basis foridentifying gaps where the waveguide performance is below the theoreticalpredictions. The fabricated waveguides presented in this thesis were based onion-exchange and precise diamond-blade dicing resulting in a ridge geometry.Moreover, waveguide grating couplers were developed on the emerging materialplatform lithium niobate on insulator.

This thesis also comprises spectral investigations of distributed-feedbacklaser resonators below lasing threshold. Here, the goal was to optimize the resonatordesign in order to maximize the photon decay time, thus minimizingthe linewidth of the emitted resonance. In particular, two scenarios were investigated,namely, a distributed-feedback resonator with a distributed phaseshift and with a thermally-chirped grating.

The research presented in this thesis adds to a growing corpus of researchtowards the development of novel and improved integrated components.