Digital filter approach for simulation of a complex integrated laser diode based on the traveling-wave model

The traveling-wave model is commonly used in the simulation of semiconductor laser diodes and photonic integrated circuits. When the laser diode is cascaded with other passive elements of relatively large optical dimension or complicated structure such as a sophisticated distributed Bragg reflector section, the conventional approach by tracing the forward and the backward traveling waveform along the entire passive section in the time domain becomes time consuming or technically impossible. To overcome this difficulty, a split-step approach is proposed in this study. Since the spectral characteristics of the passive sections are known from analytical/numerical calculations or experimental measurement, the effective time-domain digital filters are introduced for the passive components. Therefore, in the simulation, the laser diode part is still modeled by the traveling-wave approach, but the digital filters are used to model the passive components butted at the end of the active part, which interact with the optical field of the laser diode at the interface.