Tunable random laser with a cavity based on an erbium-doped germanophosphosilicate artificial Rayleigh fiber

This study is devoted to the construction and investigation of a tunable random laser with a cavity based on weak fiber Bragg gratings (the so-called artificial Rayleigh fibers) inscribed in a 3-m-long active fiber. An array of weak fiber Bragg gratings (wFBGs) is inscribed using an ultraviolet (UV) excimer laser operating in pulsed mode and a chirped phase mask during the optical fiber drawing process. The inscription of a wFBG array by a UV laser is performed using a specially designed photosensitive germanophosphosilicate preform doped with erbium ions. It is found that, in a semi-open cavity configuration, the narrow-band generation peak can be tuned within the wavelength range of 1546.5–1547.5 nm by stretching the 90 %-reflective FBGs. The resulting random lasing is characterized by a maximum efficiency of 10 % at an output power of 1 mW under backward pumping at a wavelength of 976 nm. It is established that the tunable random laser operates in continuous-wave mode with a linewidth of ∼470 Hz.