Document Type : Original Article
Laser Photonics Research Group, Engineering Physics Dept., MTC, Cairo, Egypt.
Optoelectronic Department, MTC, Cairo, Egypt.
Fiber lasers technology has grown rapidly due to the rapid advances in high power diodes, diode-to-fiber coupling schemes and doped fiber design and fabrication. Erbium-Ytterbium (Er3+/Yb3+) co-doped fiber is an attractive active medium for the fiber lasers in which Ytterbium is co-doped with Erbium to produce a spectrum in third telecoms window around 1550nm which makes them suitable sources for long range applications. In this paper the Er3+/Yb3+ fiber laser pumped by a laser diode at 980 nm is simulated using the Optiwave software. The pump source was swept from 1.25 to 5 w to extract the slope efficiency. The pump radiation was focused into the Er3+/Yb3+ fiber through an input mirror, which was 98% reflecting at 1550 nm and 99% transmitting at 980 nm. A length of 0.1 m of Er3+/Yb3+ fiber was used with an N.A. of 0.22, Er3+ ion density of 25.4 x 1024 m-3, and Yb3+ ion density of 320 x 1024 m-3. The output mirror was 50% reflecting at 1550 nm. Then the length of the fiber was swept from 1m to 5m in order to obtain optimized fiber length. The simulation results demonstrated that a laser output power of 0.8 W was obtained at 1550 nm for a launched power of 2 W with a slope efficiency of 40% and a lasing threshold of 0.4 W of launched pump power. The results also showed that the optimized fiber length was achieved at 2 m which is in a good agreement with the published similar experimental schemes.