Internal reflection from an exponential amplifying region

Abstract

The reflectance from an amplifying region in which the gain decreases exponentially with distance from the surface is calculated as a function of incident angle. The results are similar in some respects to the reflectance from a uniform amplifying layer reported previously. In particular, a singular point occurs in the reflectance for certain values of the thickness of the amplifying region. However, the results for the exponential case do not explain the previously reported observation of large reflectance from a pumped laser dye. An asymptotic form of the reflectance for a thick amplifying region is presented. The results for asymptotic case are compared with various other theories of reflection from an amplifying region.