Fig. 1. Schematic diagram for GSA and ESA dual-wavelength-pumped 2.3 µm thulium laser. GSA, ground state absorption; ESA, excited state absorption; CR, cross relaxation.

Fig. 2. Experimental arrangement for the GSA and ESA dual-wavelength LD-pumped Tm:YLF laser. IM, input mirror; OC, output coupler; BS, beam splitter.

Fig. 3. Typical laser emission spectra measured at maximum output power. SWP, single-wavelength pumping; DWP, dual-wavelength pumping.

Fig. 4. Output powers of 2.3 µm laser versus the incident 785 nm pump powers.

Fig. 5. Output powers of 2.3 µm laser versus incident 1470 nm pump powers under different given incident 785 nm pump powers. (a) T = 1.5% OC; (b) T = 2.8% OC.

Fig. 6. Output powers of 2.3 µm laser versus incident 785 nm pump power under different given incident 1470 nm pump powers. (a) T = 1.5% OC; (b) T = 2.8% OC.

Fig. 7. Output powers of 2.3 µm laser under GSA and ESA dual-wavelength pumping for different combinations of 785 and 1470 nm pump spots.

Fig. 8. Three-dimensional beam profile and power intensity distribution of 2.3 µm laser beam measured at the 1.84 W output power.