Design and performance analysis of a tunable and self-pulsation diode pumped double-clad D-shaped Yb3+-doped silica fiber laser

Abstract

Ytterbium doped silica fibers exhibits very broad absorption and emission band, from ~800 nm to ~1064 nm for absorption and ~970 nm to ~1200 nm for emission according to the cavity length. A wide range of applications for tunable ytterbium fiber laser like development of single-frequency sources for spectroscopic applications, pumping source of Pr: ZBLAN amplifier and Tm: ZBLAN up conversion laser, material processing and military applications. In this paper, a 976 nm high power fiber coupled diode laser of up to 5 W end pumped ytterbium doped multimode D-shaped fiber laser using Fabry-Perot cavity with different regime of operation with the output coupler reflectivities of 80%, 60%, and Fresnel reflection of 4%. The output laser wavelength ranges from 1041 nm to 1094 nm for a cavity length from 1 m to 10 m, respectively. The optical to optical slope efficiency of 45% at 1 m and increased to be 60% at 4 m cavity length were measured. The maximum slope efficiency of 82.12% at cavity length of 2m were investigated with Fresnel reflection output coupler, and the measured lowest threshold pump power for this configuration was 130 mW. Also, the self-pulsation phenomena were observed just at higher pumping power of more than 4W and its threshold pumping power were (4.3W, 4.5W and 4.7W) with output coupler reflectivities of (80%, 60%, and Fresnel reflection of 4%), respectively at 10 m fiber length.