Purely Gain-Coupled Distributed-Feedback Bragg Semiconductor Laser Diode Emitting at 770 nm

The transition lines of Mg, K, Fe, Ni, and other atoms lie near 770 nm, therefore, this spectral region is important for helioseismology, solar atmospheric studies, the pumping of atomic clocks, and laser gyroscopes. However, there is little research on distributed-feedback (DFB) semiconductor lasing at 770 nm. In addition, the traditional DFB semiconductor laser requires secondary epitaxy or precision grating preparation technologies. In this study, we demonstrate an easily manufactured, gain-coupled DFB semiconductor laser emitting at 770 nm. Only micrometer scale periodic current injection windows were used, instead of nanoscale grating fabrication or secondary epitaxy. The periodically injected current assures the device maintains single longitudinal mode working in the unetched Fabry–Perot cavity under gain coupled mechanism. The maximum continuous-wave output power reached was 116.3 mW at 20 °C, the maximum side-mode-suppression ratio (SMSR) was 33.25 dB, and the 3 dB linewidth was 1.78 pm.