Numerical investigation on cascaded linear-cavity Raman fiber laser based on tellurite fiber

Abstract

A numerical simulation of the 3rd-order cascaded Raman fiber laser based on tellurite fiber at 2-5 μm waveband is presented. We investigate the variation of output power, threshold and optical conversion efficiency of the 3rd-order Stokes wave with several factors as the fiber length, FBG32 reflectivity, fiber attenuation and pump power. It shows that when the fiber length is shorter than 0.5 m, the threshold decreases and the optical conversion efficiency increases with the fiber length increasing. However, when the fiber length is longer than 0.5 m, the variation of threshold and optical conversion efficiency are contrary. The optical conversion efficiency increases first and then decreases with the reflectivity increasing. When the fiber attenuation increases, the threshold increases and optical conversion deceases. The Raman fiber laser can be optimized with the most suitable tellurite fiber length of 0.5-1.0 m and the most reasonable reflectivity of the 3rd-order Stokes output FBG32 of 10%-20%. We demonstrate numerically that the 3rd- order Stokes wave can reach the maximum average power of 45.2 W and the maximum optical conversion efficiency of 45.2% corresponding to the FBG32 reflectivity of 10% and the tellurite fiber length of 0.3 m with the attenuation of 0.85 dB/m, when pumped by 2 μm light with the average power of 100 W. Our simulated results provide a valuable theoretical guidance for the design and experiment of tellurite Raman fiber laser at mid-infrared waveband.