Abstract:The threshold formula of a acousto-optically(AO) Q-switched Nd∶YAG intracavity optical parametric oscillator(OPO),side pumped by laser diode arrays,is studied.At the same experimental condition,the optical parametric properties of KTA and KTP crystals are analyzed.At the repetition rate of 4kHz,output mirror transmission of 30%,input current of 14.5A,the KTA OPO generated the highest average output power of 613.4mW at1.57μm with pulse width of 2.5ns and the peak power of 61kW.