We have investigated quasi-eigenmodes of a quadrupolar deformed microcavity
by extensive numerical calculations. The spectral structure is found to be
quite regular, which can be explained on the basis of the fact that the
microcavity is an open system. The far-field emission directions of the modes
show unexpected similarity irrespective of their distinct shapes in phase
space. This universal directionality is ascribed to the influence from the
geometry of the unstable manifolds in the corresponding ray dynamics.Comment: 10 pages 11 figure