We observe the phenomenon of priority oscillation of the unexpected σ -polarization in high-power Nd:YVO 4 ring laser. The severe thermal lens of the σ -polarized lasing, compared with the π-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd:YVO 4 crystal as the gain medium, the unexpected σ -polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected π-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no σ -polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.
By analyzing the relation between the transmission of the output mirror and the output power in an intracavity frequency doubling laser,we choose an optimal transmission of the output mirror according to the laser application requirements.As a result,a high-power single-frequency laser at 540nm is obtained with a maximum output power of 8 W and a power stability of ±1% for three hours,whose beam quality M2 is better than 1.2.At the same time,a moderate FW power of 1.2 W is coupled out,which is enough to meet the requirements for local oscillation light and injected signal optical beams in quantum optics experiments.
