Performance of ND:YVO4 diode pumped solid state laser in second harmonic generation and Q-switching

Abstract

Diode pumped solid state laser (DPSS) is one of the most popular types of laser due to its small size and low cost. However, the performance of such DPSS laser remains unstable. This instability depends on many factors including the doping level, crystal lengths and the cooling system. In order to achieve high efficiency and good quality laser, a fundamental diode pumped solid laser was designed, constructed and optimized. In this study, vanadate crystals at different doping levels comprised of 0.5, 1.0 and 1.5 at. % and thickness of 1, 3, and 10 mm were employed as a gain medium. Diode laser centered at 808 nm was used with end pumped technique. The threshold power was optimized using various kind of output coupler including 40, 45, 50, 60, 70 and 75 %. The laser was further modulated by inserting a number of nonlinear materials including KTP to produce second harmonic generation signals. Cr4+:YAG saturable absorber has been used for passive Q-switching technique. Analysis shows that the gain medium with 1.5 at. % is identified as the best doping level with low threshold power and high slope efficiency of 30 %. The best thickness of the crystal bar is identified to be at 3 mm having performance of 55 % slope efficiency with threshold power of 0.6890 W. The output coupler of 75 % reflectivity having slopeefficiency of 54 % with lower threshold power of 0.3974 W, whereas half wave plate is capable to convert almost 95 % to second harmonic generation SHG with threshold power of 0.0063 W. Pulse duration of Q-switched laser is found to be inversely proportional to the input current.