Characteristics of Whispering Gallery Modes in Single Dielectric Spheroid Excited by Gaussian Beam

We have numerically analyzed a coupling between a Gaussian light and spheroids by using a finite-difference time-domain method. In a configuration where the polarization of light is directed along the short axis of the spheroid and light is incident along the long axis, there exists a complex whispering gallery mode (WGM), which cannot be observed for any spheres. The characteristics of such a complex WGM are similar to those produced from a combination of several WGM's. In a configuration where the polarization of light is directed along the long axis of the spheroid and light is incident along the short axis, the Q -factor of a WGM excited there decreases compared with that of the WGM of a sphere because the curvature around the edges of the long axis is considerably large and thus the confinement of light must be weak.