The emission directionality of the well-studied Robnik billiard conforms well to the classical prediction we made in
Opt. Lett. 19, 1693 (1994).
Shown here is the Robnik billiard at fractional deformation 0.045
and refractive index n=2. The wavenumber on the outside is kR=43.1
(R is the undeformed radius), corresponding to kR=86.2 on the inside.
The resonant state depicted here corresponds to classical rays for which the
angle of incidence χ
with respect to the surface normal roughly satisfies
sin χ=0.7.
Such rays lie in the chaotic region of phase space.
One sees tangential escape from the
high-curvature regions.
The Poincaré section of the Robnik billiard at this deformation shows the
extent of chaos and island structure.
