Fig. 1. Schematic of orthogonally polarized dual-frequency Er ∶ YAG laser resonantly pumped by a 1532 nm fiber laser

Fig. 2. Calculated beam radius of laser along optical axis in the resonator

Fig. 3. Calculated transmittance curves for FP1 and FP2 and measured fluorescence spectrum of Er∶YAG

Fig. 4. Output power of Er∶YAG laser at 1645 nm and 1617 nm versus incident pump power

Fig. 5. Output longitudinal mode spectra of Er ∶ YAG laser. (a) P-polarization light at 1617 nm; (b) S-polarization light at 1645 nm; (c) orthogonally polarized dual-frequency light at 1617 nm and 1645 nm

Fig. 6. Measured M²-factors of Er∶YAG laser. (a) 1617 nm light; (b) 1645 nm light

Fig. 7. Measured spectrum of Er∶YAG laser

Fig. 8. Measured fluctuations of the wavelength of Er∶‍YAG laser. (a) 1617 nm; (b) 1645 nm