Short 17-cm DBR Raman Fiber Laser With a Narrow Spectrum

We present experimental results on the lasing of a short distributed Bragg reflector (DBR) Raman fiber laser (RFL) with short cavity length. The high finesse laser cavity with an effective length of 17 cm was realized by direct inscription of two Bragg gratings into a short piece of highly nonlinear polarization maintaining Raman fiber. It is pumped by an Ytterbium fiber laser at 1100 nm with up to 8 W pump power. The Stokes wave at 1151 nm is generated within the DBR RFL with 700-mW output power and a narrow spectral full-width at half-maximum bandwidth of 60 pm. Due to the short cavity length, the number of oscillating longitudinal modes is strongly reduced to less than 24 modes. The short DBR RFL has a low lasing threshold of 4.1 W. Its spectral properties and temporal stability are investigated. Distinct longitudinal cavity modes could be observed within the radio-frequency intermode-beat spectrum detected with a fast photodiode. The measured mode separation of 607 MHz validates the short effective length of 17 cm.