Single-frequency fibre laser with a cavity formed by Bragg gratings written in the core of an active composite fibre using KrF laser radiation (248 nm)

The possibility of producing a single-frequency fibre laser using a new type of fibre made by sintering phosphate glass in a silica glass tube (composite fibre) is demonstrated. In a fibre of this type, photosensitivity to laser radiation with a wavelength of 248 nm is detected. A fibre laser cavity is fabricated by writing fibre Bragg gratings directly in the core of the composite optical fibre activated by erbium ions. Stable single-frequency linearly polarised lasing regime is obtained at a wavelength of 1559.5 nm with a maximum output power of ∼3 mW.