EFFICIENT MATERIAL-GAIN MODELS FOR THE TRANSMISSION-LINE LASER MODEL

Transmission-line laser models (TLLMs) are time-domain models suitable for the simulation of complex phenomena in semiconductor lasers. TLLM s include time-domain filters based on transmission-line stubs to mode l the spectral dependence of the material gain. In this paper, numeric al simulations are presented which show that the accuracy of these gai n models is dependent on the model's iteration timestep. Analytical fo rmulae are derived that relate the accuracy of the filters to the time step, filter centre frequency, and filter bandwidth. A new wideband st ub filter which allows the material gain to be modelled using a larger timestep is presented. This is equivalent to a digital infinite-impul se-response filter, which is more computationally efficient than finit e-impulse-response filters, and is unconditionally stable. The new gai n model can improve the computational speed for simulating for multimo de Fabry-Perot lasers by a factor of 10-100.