Experimental studies on beam quality-improving of 8?m ZGP optical parametric oscillator

We report on experimental studies on the beam quality of the 8μm ZGP optical parametric oscillator(OPO). Through conducting a series of comparative experiments, the effects of resonator length, type of phase matching, resonant wavelength and structure of the resonator on the beam quality of ZGP OPO were studied respectively. By using longer resonator length (120mm), type I phase matching, longer resonant wavelength (8μm) and the ring cavity, the output with the beam quality factor of M²~1.20 and 1.22 in the horizontal and vertical direction were achieved respectively. And this is a rather good beam quality level for 8μm ZGP OPO.