Fig. 1. Schematic of the laser polarization-multiplexed by sandwiching a Yb:CALGO crystal with two birefringent crystals. LD: fiber-coupled laser diode; DCM1, DCM2: dichroic mirrors; G: Yb:CALGO cryatal; BC1, BC2: birefringent crystals made of YVO₄; HR: high reflection concave mirror with a curvature radius of 150 mm; OC: output coupler with a curvature radius of 150 mm; L1, L2: lenses; HWP: half-wave plate; PBS: polarization beam splitter

Fig. 2. Measurement results of the output power when the laser was operated in single mode. (a) Output power versus the direction of linearized laser polarization. (b) Output power versus absorbed pump power

Fig. 3. Output power of the laser when the birefringent crystals were inserted into the cavity. (a) Two polarization states exist at the same time; (b) only the ordinary light is pumped; (c) only the extraordinary light is pumped

Fig. 4. Spectra in different conditions. (a)−(c) show the spectra when no etalon was used, and (d)−(f) show the spectra when an etalon was used; (a) and (d) show the spectra when the o- and e-light coexisted, while (b), (c), (e), (f) show the spectra when only one polarization state was excited