We observe the phenomenon of priority oscillation of the unexpected a-polarization in high-power Nd：YVO4 ring laser. The severe thermal lens of the a-polarized lasing, compared with the n-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd：YVO4 crystal as the gain medium, the unexpected a-polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected zc-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no a-polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.
We present a continuous-wave squeezed vacuum generation system at a telecommunication wavelength of 1.3 μm. By employing a home-made single-frequency Nd：YVO4 laser with dual wavelength outputs as the pump source, via an optical parameter oscillator based on periodically poled KTR a squeezed vacuum of 6.1 dB＋0.1 dB below the shot noise limit at 1342 nm is experimentally measured. This system could be utilized for demonstrating practical quantum information networks.
