LD-pumped Nd: YAG Electro-optic Q-switched Laser and Its KTP Extra-cavity Frequency-doubling Characteristics

An Nd: YAG electro-optic Q-switched laser side-pumped by a laser diode and its extra-cavity frequency-doubling characteristics are reported in this paper. The laser employs a KD*P crystal as the electro-optic Q-switch and uses a combination of a 1/4 wave plate and a polarizer to achieve precise Q-switch control. Under the operating conditions of the pump power of 80W, the 1064 nm laser output with a pulse width of 10ns and a single-pulse energy of 3µJ was obtained, with a peak power of 300W. By inserting a 15mm long KTP frequency-doubling crystal outside the cavity, a 532nm single-pulse green of 1.75µJ was achieved with a frequency-doubling conversion efficiency of 58.3%. This experiment achieved high peak power pulsed output from an all-solid-state electro-optic Q-switched laser, with excellent pulse stability and energy fluctuations of less than ±1%. The results demonstrate that the KD*P crystal, as an electro-optic Q-switch, enables precise Q-switching control and generates laser output with narrow pulse width. Furthermore, the frequency-doubling crystal KTP is highly suitable for frequency doubling 1064nm laser radiation, achieving high conversion efficiency at moderate power densities. This study also effectively addressed potential thermal effects during laser operation by implementing a water-cooling system and optimized heat sink design, which successfully controlled the temperature of the Nd: YAG crystal, KD*P electro-optic crystal, and KTP frequency-doubling crystal.