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

Lateral-mode discrimination by misaligned total internal reflection (TIR) mirrors in multimode ridge waveguide structures is proposed. The effects of angular misalignment in TIR mirrors and index steps in ridge waveguides on the modal reflectivity is analyzed by a plane wave expansion method, The modal reflectivity of a high-order mode decreases more 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-mode discrimination over high-order modes if the ridge waveguides have large index steps.