Fig. 1. Experimental setup for 1.5–1.6 µm Er:Yb:YAB tunable laser.

Fig. 2. Transmission curves at 1470–1620 nm of the IM and OMs.

Fig. 3. Room-temperature gain cross section spectra at 1450–1650 nm of a c-cut Er:Yb:YAB crystal for different β.

Fig. 4. Wavelength tunability of the CW laser at an incident pump power of 3.0 W and an OM transmission of 1.2%. (a) Tuning laser spectra and output powers; (b) output powers and room-temperature gain spectrum at β = 0.45.

Fig. 5. Experimental setup for measuring the temperature inside the Er:Yb:YAB crystal during the 1.5–1.6 µm laser operation.

Fig. 6. Temperatures at the waist spot position of the pump beam in the crystal for different pump powers when the 1.5–1.6 µm laser is operating. The insets show the upconversion fluorescence spectra at 510–570 nm recorded at some pump powers.

Fig. 7. Gain cross section spectra at 1510–1630 nm of a c-cut Er:Yb:YAB crystal at different temperatures T for β = 0.5.

Fig. 8. Wavelength tunability of the CW laser at an incident pump power of 5.3 W and an OM transmission of 1.2%. (a) Tuning laser spectra and output powers; (b) output powers and gain spectra of the crystal at 300 and 550 K for β = 0.65.

Fig. 9. Energy level diagram of Er³⁺ in the YAB crystal and ion population ratios of all Stark energy levels at 300 K and 550 K.

Fig. 10. Wavelength tunability of the CW laser at an incident pump power of 7.7 W and an OM transmission of 1.2%. (a) Tuning laser spectra and output powers; (b) output powers and gain spectra of the crystal at 300 K and 700 K for β = 0.75; (c) spectrum as well as images of the transversal profile for the laser beam.

Fig. 11. Wavelength tunability of the CW laser at an incident pump power of 7.7 W for different OM transmissions T. (a) T = 2.6%. (b) T = 4.7%.