The correspondence between ray and wave descriptions for twodimensional
chaotic open billiards describing optical cavities is reviewed.
Focusing on the stadium-shaped cavity, which is well-known
for its fully chaotic ray dynamics, we show how ray chaos is manifested
in emission patterns, or eigenfunctions of resonances (decaying
eigenmodes). The flux phase-space distribution is introduced, which
not only enables one to understand the relation between ray dynamics
and emission directionality, but also provides a suitable stage to study
the ray-wave correspondence. We observe intrinsic localization phenomenon
in each resonance, which causes discrepancies with the ray
description. Nonetheless, we demonstrate that the average of many
low-loss resonances reproduces the ray description very well, where one
can clearly observe that signature of ray chaos (i.e., long-term effects
of stretching and folding) is embedded in resonance eigenfunctions.
