OPTICAL TUNNELING FROM ONE-DIMENSIONAL SQUARE-WELL POTENTIALS

The authors study a one-dimensional model for optical tunnelling with a refractive index in the shape of a square well. The relevance of the model and its limiting cases are discussed. The main result is the leading behaviour of the exponentially small imaginary part of the eigenvalue which determines the radiation loss. The leading behaviour of the imaginary part is calculated using Berry's formula which controls the asymptotic expansion of the Airy function Bi(z) to better-than-exponential accuracy.