Thermal effect investigation and passively Q-switched laser performance of composite Nd:YVO4 crystals

• The focal lengths of the composite and conventional Nd:YVO4 crystals have been studied.
• The composite crystal could effectively reduce the thermal lens effect.
• The laser performance of the composite crystal is superior to the single crystal.
• The combination of different composite crystals and output coupler can get the needed laser performance.

Diode-pumped continuous-wave (CW) and passively Q-switched composite Nd:YVO4 lasers are presented by using Cr4+:YAG as saturable absorber. The temperature distributions and thermal focal lengths in three Nd:YVO4 crystals are numerically analyzed by a finite element method and the results show that diffusion-bonding composite crystals can effectively reduce the thermal lens effect. CW and passively Q-switched laser performances are experimentally investigated. The maximum CW output power of 3.35 W with an optical slope efficiency of 54.6% was obtained by Nd(0.1 at%):YVO4/Nd(0.5 at%):YVO4/Nd(1.0 at%):YVO4 composite crystal under an incident pump power of 6.52 W. The largest single pulse energy of 4.4 μJ with a pulse duration of 22 ns at a 166 kHz pulse repetition rate was also achieved.