LATERAL-MODE DISCRIMINATION IN RIDGE WAVE-GUIDES BY MISALIGNED TOTAL INTERNAL-REFLECTION MIRRORS

Lateral-mode discrimination by misaligned total internal reflection (T IR) mirrors in multimode ridge waveguide structures is proposed. The e ffects of angular misalignment in TIR mirrors and index steps in ridge waveguides on the modal reflectivity is analyzed by a plane wave expa nsion method, The modal reflectivity of a high-order mode decreases mo re rapidly than that of a fundamental mode as the angular misalignment of Tm mirrors increases. It is found that a fundamental mode can have high modal reflectivity (similar to 0.9) with significant lateral-mod e discrimination over high-order modes if the ridge waveguides have la rge index steps.