Intensity transformation by rectangular tapered reflective coupling.

A complete analysis of light propagation through a hollow coupling with a uniformly varying cross section and specularly reflecting walls is given. This enables one to relate the entrance and exit intensity distributions when the input is incoherent but collimated. Results indicate that the input aperture can be partitioned into sections characterized by the total number of reflections an incoming ray has within the coupling. Input radiation in every section is linearly spread over the entire exit aperture. Hence nonuniformities in the input intensity profile are reduced at the output. This effect can be enhanced by proper design as discussed in the paper.