Highly-photosensitive Er/Yb-codoped fiber for single-frequency continuous-wave fiber lasers with a short cavity for telecom applications

A new active optical fiber with germano-phosphosilicate core, co-doped with Er and Yb, was developed by means of MCVD technology. This fiber has a high UV photosensitivity to the radiation of the 193 nm excimer laser. This feature allows us to avoid hydrogen loading of this fiber for the inscription of the Bragg gratings forming the cavity of a fiber laser. The parameters of this fiber, such as absorption and gain spectra, as well as photosensitivity, have been studied in detail. It was shown that high-performance single-frequency fiber lasers can be developed based on this fiber. A Fabry-Perot laser cavity with two fiber Bragg gratings was created based on a 30 mm long "pristine" (non-hydrogenated) fiber segment by means of the 193-nm radiation of the excimer laser. The slope efficiency of this laser was found to be 17% and the linewidth of about 88 kHz.