First principles analysis of asymmetric reflectivity in an abruptly-stepped dielectric waveguide

With its unique cavity structure, the triangular ring laser has the potential for low threshold and low noise operation. The noise is lowered by achieving unidirectional operation with asymmetric elements which favor one circulating direction over the other. Use of an "optical diode" or tapered waveguides has been shown to enhance the asymmetry in the output beams. To model the electro-magnetic wave propagation inside this structure, a 3-D analysis is essential due to its complex geometry with sharp corners. The Beam Propagation Method and conventional 2-D modeling are limited in this respect.