高功率棒状固体激光放大器输入激光光束变换研究

Investigations on Transform of Laser Beam Inputting to the Laser Rod of High-Power Solid-State Laser Amplifier

提出了研究入射高斯光束在固体激光放大器激光棒内光斑半径分布及准确计算棒内模体积的新方法。利用该方法研究了热透镜效应、入射高斯光束束腰半径及衍射倍率因子3个因素对入射光束沿放大器激光棒的光斑半径分布及模体积的影响。研究结果表明,对于高功率固体激光放大器,当输入激光棒发散角较小的准直光束时,由于棒内强烈的热透镜效应,光束向激光棒中轴线产生较大的偏折,从而使入射光束在激光棒内模体积减小,入射光束与抽运能量的重叠效率下降。而采用发散角较大的入射光束,由于光束自身的发散可抵消较强的热透镜效应对光束的偏折,从而在激光棒内可获得较大的入射光束模体积及重叠效率。另外对于多模入射激光束,由于其发散角较大,应采用较大束腰半径的光束入射。

A new method for calculating the beam radius volume in the laser rod of a solid-state laser amplifier is thermal lens effects in the rod of amplifier and the waist distribution of the input Gaussian beam and the laser mode reported. By this method, we investigate how the strong radius and mode of the laser beam inputting to the rod of amplifier influence the input laser beam distributions and input beam mode volume in the rod of amplifier. It is shows that the expanded and collimated laser beam inputting to the rod of amplifier will be strongly reflected to the axis of the rod by the strong thermal lens effects in the rod, because the small far-field divergence angle of the collimated input laser beam results in the signigicant decrease of the mode volume of input laser beam and the overlap efficiency of amplifier drops. It can obviously increase the mode volume of input laser beam in the rod of the amplifier to input the laser beam with larger angle, which can counteract the reflecting effects on the input laser beam. Moreover, the beam waist radius of the multi-mode laser beam inputting to the amplifier should be larger than that of the fundamental-mode input laser beam, since its far-field divergence angle is larger than that of the fundamental-mode laser beam with the same beam waist radius.