Ray-wave correspondence in the nonlinear description of stadium-cavity   lasers
  We show that the solution of fully nonlinear lasing equations for stadium cavities exhibits a highly directional emission pattern. This directionality can be well explained by a ray-dynamical model, where the dominant ray-escape dynamics is governed by the unstable manifolds of the unstable short periodic orbits for the stadium cavity. Investigating the cold-cavity modes relevant for the lasing, we found that all of the high-Q modes have the emission directionality corresponding to that of the ray-dynamical model. 
Susumu Shinohara, Takahisa Harayama, Hakan E. Tureci, A. Douglas Stone