Diffraction model of a semiconductor amplifier

A three-dimensional diffraction model of a semiconductor heterostructure amplifier is developed. The model describes the field propagation and optical mode establishment taking into account the amplification kinetics within the framework of the diffusion equation for current carriers in a quantum well. The results of application of this model are presented for an amplifier with an asymmetric broad waveguide and an antiwaveguide structure in the lateral direction that does not confine the field. It is shown that the length of establishment of the fundamental mode for such a structure is comparable with the length over which a weak signal is enhanced by two orders of magnitude. The balance between the gain and loss for the steady-state mode as a function of the waveguide insert width is analysed. The effect of this width on the properties of the fundamental optical mode, including the far- field intensity distribution, is studied.