Microcavity with Output Waveguide by Different Connection Angles

The present paper does a theoretical and numerical investigation of a circular microcavity connected with an output waveguide using different connection angles. The simulation results indicate that, the proportions of the WGM components, which constitute the high-Q lasing mode, change with the different connection angle between the microcavity and the output waveguide. By finely adjusting the connection angle, the field in the cavity can have one dominant propagation direction leading to increment of the output efficiency and improvement of the far-field pattern. The propagation constant of the lasing mode and waveguide fundamental mode can achieve the same direction under certain connection angle resulting in stronger coupling between the lasing mode and the waveguide fundamental mode, so that the circular microcavity can achieve unidirectional output emission with narrow angular divergence.