Modal Interactions in Microstadium Optical Cavities

The morphological dependence of resonance modes in microstadium optical cavities was investigated numerically using the finite element method by changing the length of the straight segments, which connect two half-circles. Two mechanisms resulting in deformation of the mode patterns were confirmed. One is the morphological effect of the cavity and the other is modal interactions such as mode mixing and mode exchange. When the cavity size is much larger than the resonance wavelength, the modal interactions become prominent due to an increase in the mode density, playing a significant role in the formation process of wave chaotic modes that exhibit very complicated mode patterns in microstadium optical cavities.