Narrow-linewidth external cavity semiconductor laser based on permanent index modulated grating optical feedback for radiation resistance

We demonstrate a narrow-linewidth external cavity semiconductor laser (ECSL) based on permanent index modulated Bragg grating feedback for radiation resistance. The frequency selection device of the laser is a highly stable fiber Bragg grating (FBG) created with a femtosecond laser. The laser shows excellent radiation resistance after passing through radiation, which is assessed with a γ-ray total ionizing dose (TID) radiation test. The Lorentz linewidth and relative intensity noise (RIN) of the laser show almost no change after irradiation, and are less than 15 kHz and −150 dBc/Hz, respectively. The maximum output power and laser wavelength slightly change after irradiation increasing by 3.79% and redshifting by 9.10 p.m., respectively, compared with those before irradiation. The experimental results show that the compact-structure and low-cost semiconductor laser based on the permanent index modulated Bragg grating has outstanding stability and robustness against harsh-radiation environments, and it can meet the radiation resistance requirements of space laser communication applications for light sources.