腔镜倾斜扰动对正支共焦腔输出光束模式的影响

针对激光器出光过程中腔内像差扰动带来的光束质量下降问题,分析了正支共焦腔腔镜倾斜扰动对调腔光模式的影响,采用等效透镜波导法计算了凹、凸腔镜倾斜失调状态下的调腔光模式分布、泽尼克(Zernike)像差系数。同时采用哈特曼-夏克(Hartmann-Shack)波前传感器方法对此进行了实验定量研究,用模式法进行了波前重构。得到了扰动量与泽尼克像差的定量关系。结果表明,凹镜倾斜扰动对腔模的影响大于凸镜,对于大菲涅耳数非稳腔,腔内倾斜扰动量与腔外泽尼克倾斜系数具有良好的线性关系,若对凹、凸腔镜分别施加等量倾斜扰动,带来的腔外泽尼克倾斜系数比率约为光腔放大倍率。且腔模倾斜像差增加的同时还将导致离焦、像散等高阶像差的增大,因此作腔内相位补偿或校正时,应使补偿或校正平面尽可能靠近凹面镜;最后对实际激光束与He-Ne调腔光束的异同作了简要比较。

Influence on Outcoupled Mode by Introducing Intracavity Mirror Tilt Perturbation

The result of influence on outcoupled mode by introducing intracavity mirror tilt-perturbation in positive-branch confocal resonator is analyzed.The intracavity mode distribution and its Zernike-aberration coefficient due to the concave or convex mirror tilt disadjustment are calculated by adopting equivalent lens method.At the same time,the experimental study about the relations of intracavity mirror tilt disadjustment and mode aberration has been performed by using Hartmann-Shack(H-S) wavefront sensor method.Aberrations of outcoupled beam mode are obtained by using mode-reconstitution method.The results show that the intracavity perturbation of concave mirror has a greater effect on outcoupled beam-quality compared with that of convex mirror.For the large Fresnel-number resonator,the tilt angle of intracavity mirror has a close linear relationship with extracavity Zernike tilt aberration coefficient.The ratio of Zernike tilt coefficient approaches to the magnification of unstable resonator if equivalent perturbation is applied to concave mirror and convex mirror respectively.Furthermore,astigmatism and defocus aberration are also increased with the augment of tilt aberration of beam mode.So intracavity phase-corrected elements used in unstable resonator should be close to the concave mirror.The wavefront relationship between the He-Ne laser and the actual laser beam has also been compared.