Mode characteristics of metallically coated square microcavity connected with an output waveguide

Abstract

Mode characteristics of a square microcavity with an output waveguide on the middle of one side, laterally confined by an insulating layer SiO2 and a p-electrode metal Au, are investigated by two-dimensional finite-difference time-domain technique. The mode quality (Q) factors versus the width of the output waveguide are calculated for Fabry–Pérot type and whispering-gallery type modes in the square cavity. Mode coupling between the confined modes in the square cavity and the guided modes in the output waveguide determines the mode Q factors, which is greatly influenced by the symmetry behaviors of the modes. Fabry–Pérot type modes can also have high Q factors due to the high reflectivity of the Au layer for the vertical incident mode light rays. For the square cavity with side length 4 μm and refractive index 3.2, the mode Q factors of the Fabry–Pérot type modes can reach 104 at the mode wavelength of 1.5 μm as the output waveguide width is 0.4 μm.