Distributed Bragg reflector fiber laser directly written in a composite fiber manufactured by melting phosphate glass in a silica tube.

We demonstrate a single-frequency distributed Bragg reflector (DBR) fiber laser based on the novel erbium-doped composite fiber fabricated by melting phosphate glass in a silica tube. The fabricated composite fiber was single-mode at the wavelength of 1.55 μm; the measured cutoff wavelength was 1.4 μm. The composite fiber was photosensitive to irradiation at the wavelength of 193 nm. Using the phase mask method, the DBR fiber laser cavity with the total length of 21 mm was inscribed directly into the erbium-doped composite fiber. A stable single-frequency regime of the fabricated DBR laser at the wavelength of 1565 nm is demonstrated.