Design and experiment of unstable resonator for high-power TEA CO_2 laser

With the aim to improve the laser beam quality and to keep the high output power for a high-power TEA CO2 laser,three sets of telescopic positive-branch confocal resonators are designed by using a unstable resonator scheme based on a original stable resonator,and the whole design process and theoretical analysis are given.The corresponding comparison experiments are conducted for single-pulse energy,divergence angles and pulse duration time.Experimental results indicate that using unstable resonator not only can largely improve the divergence angle,but also can maintain the high single-pulse energy for the TEA CO2 laser.When the designed unstable resonator is in the best combination state,it can provide the single-pulse energy of 13.7 J,a divergence angle of 1 mrad(stable resonator as 2.4 mrad) and the pulse duration time of 50 ns(stable resonator as 98 ns),which shows this work will contribute to this kind of laser to be widely used in the field of laser manufacture.