High-efficiency gain-coupled distributed feedback semiconductor laser achieved using a metal surface grating

This study demonstrates a pure gain coupling laser achieved through periodic injection using a metal surface grating. To enhance both the gain contrast and the grating coupling factor, the grating coverage width was optimized to 20 µm. Unlike conventional approaches that employ an insulating layer etching for periodic electrode injection, the lift-off method was adopted to fabricate the grating, effectively preventing chip short circuits during grating the width expansion. The device achieves a single-mode continuous-wave (CW) output of 100 mW at an injection current of 200 mA, with the lasing wavelength centered at 1.09 µm and a slope efficiency of 0.58 W/A and a side-mode suppression ratio exceeding 42 dB. Furthermore, it maintains stable single-mode operation with a spectral tuning range exceeding 12.2 nm within a temperature variation of 30 °C. Owing to its simplified fabrication process and reliable performance, this method offers a practical and low-cost solution for manufacturing gain-coupled distributed feedback lasers.