Fig. 1. Schematics of experimental setup and power and conversion efficiency curves of homemade 1973 nm laser. (a) Experimental setup for bidirectional pumping of 3.5 μm fiber laser; (b) schematic of homemade 1973 nm pump light source; (c) output power and conversion efficiency curves of homemade 1973 nm laser

Fig. 2. Output power curves of 3.5 μm fiber laser by unidirectional pumping. (a) Backward pumping; (b) forward pumping

Fig. 3. Energy levels of 3.5 μm Er∶ZBLAN fiber laser

Fig. 4. Output power curve of 3.5 μm fiber laser by bidirectional pumping

Fig. 5. Output spectra of 3.5 μm fiber laser under different pump powers

Fig. 6. Beam quality and output beam profile of 3.5 μm fiber laser

Fig. 7. Power change of each wavelength laser in 3.5 μm fiber laser cavity and heat distribution under different pumping schemes