Far-Field Emission Patterns and the Emission Positions of Individual Cavity Modes in a Highly Deformed Microcavity

The characteristics of quasi-bound states of a highly deformed microcavity were investigated in both theory and experiment. Five distinct mode groups were observed with cavity quality factors different by several orders of magnitude in the range of 10⁴ - 10⁶. Consistently they had quite different intracavity mode distributions. However, their far-field emission patterns were found to be almost identical, contrary to common understanding that the emission direction is usually associated with the internal mode distribution. Both the observed far-field patterns and emission positions support that the output emissions are mostly due to the refractive escape at the common emission points determined by the unstable manifold of ray trajectory crossing the critical line of total internal reflection regardless of mode groups.