36.5 W high-power 976 nm first-order DFB semiconductor diode

High-power 976 nm semiconductor lasers are the core pump sources for ytterbium-doped fiber lasers (YDFLs). This paper reports a 976 nm distributed feedback (DFB) semiconductor laser that achieves an outstanding high-power continuous-wave (CW) output. Based on an epitaxial structure with extremely low internal loss, we calculated the influence of grating coupling strength on the longitudinal spatial hole burning (LSHB) effect under high-power conditions, and delicately designed the physical parameters of the first-order grating of the device. We fabricated a perfect sinusoidal first-order grating through ultraviolet (UV) nanoimprint lithography and dry etching processes. Testing indicates that at 20 °C, the CW output power of the device reaches up to 36.5 W (@ 35 A), the peak wall-plug efficiency reaches 59.4% (@ 11.9 A), and the spectral width under the operating current is 0.5 nm. Within a wide temperature range of 15 °C to 50 °C, the device achieves wavelength locking, with a temperature drift coefficient of only 0.074 nm/°C. In the operating range of 20 A to 35 A, the device exhibits a mode-hop-free continuous output spectrum, with a current drift coefficient as low as 0.162 nm/A.