Investigations on beam quality improvement of an NCPM-KTA-based high energy optical parametric oscillator using an unstable resonator with a Gaussian reflectivity mirror [Invited]
Jun Meng, Chen Li, Zhenhua Cong, Zhigang Zhao, Shang Wang, Gaoyou Liu, Zhaojun Liu
Abstract
Beam quality improvements by a large margin for signal and idler beams of a high energy 100 Hz KTiOAsO 4 (KTA) non-critical phase matching (NCPM) optical parametric oscillator (OPO) were demonstrated using an unstable resonator configuration instead of a plane-parallel one. Theoretically, influences of cavity lengths and transmission of an output coupler on the OPO conversion efficiency for both were numerically simulated. For OPO based on an unstable resonator with a Gaussian reflectivity mirror, the maximum pulse energies at the signal (1.53 m) and idler (3.47 m) were about 75 mJ and 26 mJ, respectively. The corresponding beam quality factors of the signal were M x 2 = 9.8 and M y 2 = 9.9, and M x 2 = 11.2 and M y 2 = 11.5 for the idler. As a comparison, 128 mJ of signal and 48 mJ of idler were obtained with the plane-parallel resonator, and the M 2 factors of the signal were M x 2 = 39.8 and M y 2 = 38.4, and M x 2 = 32.1 and M y 2 = 31.4 for the idler. Compared with a plane-parallel cavity, over eight times and three times brightness improvements were realized for the signal and idler light, respectively.