Time-domain optical wave propagation in disordered and nonuniform guiding structures

We formulate a time-domain numerical approach to optical wave propagation based on a locally one-dimensional implicit finite-difference approximation to the two-dimensional scalar wave equation and show how it can be used to study the nature of wave propagation in optical and optoelectronic devices with spatial nonuniformities and disorder. The technique is particularly well suited for the visualization of complex scattering and diffraction phenomena. We estimate the influence of interface roughness in semiconductor lasers with mirrors defined by etching processes as a function of a feature depth parameter and an in-plane correlation length. The reflectivity falls off exponentially with their product for small disorder yet remains close to its unperturbed value for the disorder scale attainable with the state-of-the-art etching technology. It is also shown how this approach can be applied to the design of an optically controlled heterojunction bipolar transistor, in which the Light enters from a lateral waveguide and must be absorbed in the base-collector depletion region.