Design and optimization of distributed feedback lasers with low relative intensity noise

Distributed feedback (DFB) semiconductor lasers with low relative intensity noise (RIN) are in demand for high-power and narrow-linewidth applications. However, there is a lack of research on the compatibility of these features, together with RIN degradation at high temperature. In this paper, the RIN characteristics of InGaAsP multi-quantum-well DFB lasers are studied through theoretical calculation and numerical investigation, the results of which are very close. Based on numerical simulation, the epitaxy layers and optical cavity structures of DFB lasers are optimized to improve the RIN performance. The simulation results show that a high-power laser with an output power up to 400 mW and a narrow-linewidth laser with a linewidth below 300 kHz can obtain a peak RIN below -166 dB/Hz and -160 dB/Hz from 0.1 to 20 GHz, respectively, meeting the requirements of light sources for microwave photonics system and coherent optical transceiver system. In terms of thermal effect, buried heterostructure lasers could effectively mitigate the deterioration of RIN compared to ridge waveguide lasers due to better temperature characteristics.