Intra-cavity Frequency-doubled Green Pulse Laser Based On PPLN Crystal

LD-pumped all-solid-state passive Q-switched green pulse lasers are widely applied to material processing, atmospheric detection, spectral analysis etc., due to the good beam quality and high peak power. A highly efficient 808nm LD pumped 1064nm Q-switched laser has been designed with the Nd:YVO4 crystal as the gain medium and the Cr4+:YAG crystal as the saturable absorber. Further, green pulse laser with high repetition rate and narrow pulse duration is achieved when the periodically poled lithium niobate (PPLN) doubling frequency crystal is inserted in the resonator.Firstly, the main parameters of the Q-switched laser such as the peak power, the pulse energy and the energy efficiency of a single pulse are obtained by numerical solutions based on the rate equation. Then, the physical and optical properties of two kinds of laser crystals (Nd:YVO4 and Nd:GdVO4) are introduced in detail. Through systematic analysis and comparison,at last,the Nd:YV04 is chosen as the laser working material in our experiment. In addition, the optical properties of the PPLN crystal are also discussed and the optimal grating period and its working temperature are obtained by numerical simulations.In the experiment,a linear cavity of 808nm LD pumped 1064nm pulse laser is designed based on the Nd:YVO4/Cr4+:YAG crystals. The experimental results show that, under the absorbed pump power of 4.5W, the output power of 1.04W for the 1064nm pulse laser is achieved with the repetition rate,the pulse duration,and the optical-optical conversion efficiency of 44.32KHz, 78ns, 23.11%, respectively.Furthermore, 532nm green pulse laser is obtained by substituting the 1064nm cavity mirror with the PPLN crystal, whose right facet is high reflection coated for 1064nm.The experimental results indicate that, under the absorbed pump power of 4.5W, the average output power of 452mW for the green pulse laser is achieved and the repetition rate, the pulse duration and the optical-optical conversion efficiency are 38.9KHz, 40ns, 10%, respectively.