Directional emission of stadium-shaped micro-lasers
  The far-field emission of two dimensional (2D) stadium-shaped dielectric cavities is investigated. Micro-lasers with such shape present a highly directional emission. We provide experimental evidence of the dependance of the emission directionality on the shape of the stadium, in good agreement with ray numerical simulations. We develop a simple geometrical optics model which permits to explain analytically main observed features. Wave numerical calculations confirm the results. 
M. Lebental, J.-S. Lauret, J. Zyss, C. Schmit, and E. Bogomolny