Single-frequency erbium laser with random distributed feedback implemented on phase mask inhomogeneities

We present a ∼1555.8-nm single-frequency erbium laser with random distributed feedback implemented on phase mask inhomogeneities upon writing a single highly reflective fibre Bragg grating. The spectrum of such a grating contains asymmetric side resonances located predominantly in the long-wavelength region of the spectrum. At the wavelength of one of the dips separating these resonances, single-frequency lasing with a linewidth of ∼1 kHz is observed at a maximum output power of 0.74 mW obtained at a pump power of 540 mW. The power and spectral characteristics of the presented laser are comparable with those of a regular laser with distributed feedback.