Single-frequency erbium-doped fibre laser with random distributed feedback based on disordered structures produced by femtosecond laser radiation

Inscription of structures by a femtosecond laser beam allows one to produce disordered structures capable of increasing the Rayleigh backscatter intensity in the fibre at relatively low induced losses, which makes them potential candidates for use as reflectors in fibre lasers. Here we report a narrow-band erbium fibre laser with random distributed feedback produced by femtosecond laser writing in half-open cavity and ring cavity configurations. In the half-open cavity configuration, single-frequency lasing is observed at output powers up to 2.8 W, with a linewidth near 10 kHz. In the ring cavity configuration, single-frequency operation is observed over the entire range of output powers studied. At the highest output power, 7 mW, the linewidth does not exceed 0.7 kHz.