TIME-DOMAIN OPTICAL-WAVE PROPAGATION IN DISORDERED AND NONUNIFORM GUIDING STRUCTURES

We formulate a time-domain numerical approach to optical wave propagat ion based on a locally one-dimensional implicit finite-difference appr oximation to the two-dimensional scalar wave equation and show how it can be used to study the nature of wave propagation in optical and opt oelectronic devices with spatial nonuniformities and disorder, The tec hnique is particularly well suited for the visualization of complex sc attering and diffraction phenomena. We estimate the influence of inter face 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 thei r product for small disorder yet remains close to its unperturbed valu e 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 d esign 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.