Examining the generation modes of an erbium-doped fiber laser with distributed feedback

Subject of study. The subject of this study is the analysis of the parameters and optical characteristics of a distributed feedback (DFB) laser based on a single fiber Bragg grating (FBG) with a constant period inscribed in an erbium-doped optical fiber. Aim of study. The aim was to determine the dependence of the radiation generation mode of a DFB laser, based on a single FBG with a constant period recorded using the phase mask method, on the pump power and resonator length. Method. FBGs were inscribed using the phase mask method via optical beam translation of a KrF excimer laser with a central wavelength of 248 nm. Structures with lengths ranging from 40 mm to 70 mm (in 5 mm steps) and reflection coefficients exceeding 99% were recorded in a FiberCore I-25(980/125) optical fiber under low-temperature hydrogen loading. A pump diode, with a central wavelength and maximum output of 980 nm and 435 mW, respectively, was used. The correlations between the radiation parameters and variations in the FBG length and pump power were measured. Main results. The variations in the generation mode of the DFB laser on pump and resonator parameters were analyzed. The results showed that stable radiation can be generated, at pump powers up to 435 mW, using a single 45-mm-long FBG with a constant period (recorded using the phase mask method in an erbium-doped fiber), without requiring π -phase-shifted structures or longer gratings (recorded using the step-by-step method). Practical significance. The results obtained can be applied to simplify optical schemes and optimize the performance of measurement systems based on DFB fiber lasers.