Progress on high power quasi-continuous-wave sodium beacon laser

A 33W 589 nm sodium beacon laser with the linewidth of 0.4 GHz and the beam quality of M² = 1.2 is achieved by sum-frequency mixing 1064 nm and 1319 nm quasi-continuous-wave (QCW) diode-pumped Nd:YAG lasers with a LBO crystal. The repetition rate of the laser is 500 Hz with the pulse width of 120 μs. Compared with the continuous-wave (CW) sodium beacon laser, the QCW microsecond-pulse sodium beacon laser can provide a gatable pulse format to eliminate the interference of atmospheric Rayleigh scattering and reduce stretching phenomenon of the imaging spot for sodium guide star, so the better correction effect can be achieved by using the adaptive optics system with the microsecond-pulse laser. A microsecond-pulse sodium beacon laser prototype is developed to generate a sodium laser guide star which is observed by the 1.8m telescope in Yunnan province.