Developing coupled wave theory for photonic crystal surface emitting lasers

Photonic crystal surface emitting lasers (PCSEL) are an emerging form of semiconductor laser diode which provide simultaneous high power, narrow divergence, narrow line width, immense beam functionality, on-chip testing, and cost-effectiveness, all whilst in a compact form. The vast majority of research in the field is restricted to TE-polarised square lattice PCSELs where a large refractive index contrast is required. In this thesis, three-dimensional coupled-wave theory (3D-CWT) is developed and implemented to investigate alternative PCSEL configurations, including triangular lattice geometries and TM polarisation. These configurations remain relatively underexplored in the literature, yet they exhibit characteristics that may offer advantages over conventional designs. As such, they may provide an additional platform for realising PCSELs tailored to specific applications.