Design of erbium doped double clad ZBLAN Fibre laser

A high powered octagonal double clad ZBLAN (33 μm/330 μm, NA=0.13) glass fibre for mid-infrared light generation is studied using a one dimensional rate equation model. The fibre laser design employs the concept of cascade lasing and includes up-conversion phenomena. The results obtained demonstrate that efficient cascade lasing may be achieved in practice without the need for fibre grating fabrication, as a sufficient level of feedback for laser action is provided by Fresnel light reflection at ZBLAN glass fibre air interfaces. Further enhancement of the laser efficiency can be achieved by terminating one of the fibre ends with a mirror. Simulation results show that the laser operation with 20 W of pump power at 0.98 μm wavelength can be achieved at 2.75 μm operating wavelength with Er 3+ ion concentrations of 60,000 ppm.