Ultra-high-temperature resistant distributed Bragg reflector fiber laser based on type II-IR fiber Bragg gratings.

We demonstrate a distributed Bragg reflector fiber laser that is capable of long-term operation at ultra-high temperatures. To form the laser cavity, a piece of Er-doped fiber is fusion spliced to a pair of type II-IR gratings, which are written using a femtosecond laser with a phase mask. Saturated gratings with different reflectivities are fabricated by varying the position of the grating region relative to the fiber core center. An eccentric grating with a relatively low reflectivity is chosen as the laser output coupler, while a regular grating with a higher reflectivity is used as the laser's high-reflection reflector. After an annealing process, the laser performance is tested at high temperatures. The results show that the laser can operate with a stable output wavelength and no output power degradation at high temperatures up to 1000°C.