Modelling of semiconductor laser with double external cavities for use in ultrahigh speed photonics

We model and investigate the dynamics and modulation performance of semiconductor laser integrated with two short external cavities facing the front and back facets with the aim to enhance the modulation bandwidth of the laser for use in high-speed photonics. The coupled cavities provide double optical feedback (DOFB) to the laser cavity through the partially reflecting facets of the laser cavity. The study is based on modifying the rate equations of the laser to include multiple reflections of laser radiations in the external cavities. Therefore, it accounts for the regime of strong OFB that causes bandwidth enhancement. We introduce correspondence between the laser stability under DOFB and the modulation response characteristics. Also, we allocate the ranges of the DOFB that induce photon–photon resonance (PPR) effect as the main contributor to the bandwidth enhancement. We show that the intensity modulation (IM) response can be tailored by varying the reflectivity of the external mirrors when the external cavities are too short to stabilise the laser output. Modulation bandwidth better than 55 GHz is predicted under strong double OFB when the external cavities are as short as 2 mm. Stronger DOFB is found to enhance the PPR effect and induce resonant modulation over a narrow frequency range around frequencies reaching 45 GHz.