Design and Performance Analysis of a Tunable and Self-Pulsation Diode Pumped Double-Clad D-Shaped Yb3+ - Doped Silica Fiber Laser

Ytterbium doped silica fibers exhibits very broad absorption and emission band, from similar to 800 nm to similar to 1064 nm for absorption and similar to 970 nm to similar 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.