输出环状光束的新型激光谐振腔

提出一种输出环状光束的新型激光谐振腔，即在稳定激光谐振腔中采用外环耦合方式得到环状光束的输出。利用For-Li数值迭代算法求解此类激光谐振腔的积分方程，通过计算机编程计算了平面一凹球面稳定谐振腔的输出端平面镜在不同半径的情况下，谐振腔镜面上和衍射耦合输出场基模的振幅和相位分布。计算结果预示了当输出端平面镜半径小于通常的稳定腔的基模半径时，衍射耦合输出场有稳定的环状光束输出。实验中TEA CO2激光器采用印刷电路板预电离结构，增益长度90cm，腔长5m，球面全反射镜曲率半径20m，输出端平面镜半径4．5mm，得到了内环半径为4．5mm、外环半径为5．5mm的基模环形光斑输出。从而在理论上和实验上证实了该方案产生环状光束的可行性。

A New Type of Laser Resonator with Annular Output Beam

A new type of laser resonator with annular output beam is presented. Annular output beam is obtained by outer ring coupling in a stable laser resonator. The integral equation of this type of laser resonator is resolved by using Fox-Li numerical iteration method. Amplitude distributions and phase distributions of fundamental mode of the diffraction-coupling output field and the fields on the surfaces of the mirrors are computed by computer programming when the output plane mirror's radius varies in a plane-concave stable resonator. The theoretical results predict that there exists steady diffraction output field with annular beam distribution when the output plane mirror's radius is less than that of the fundamental mode in an usual stable resonator. Experimental TEA CO2 laser with printed circuit board preionization is used. The laser has gain length of 90 cm. The resonator is composed of a total-reflective concave spherical mirror of curvature radius 20 m and a total-reflective plane mirror of mirror radius 4. 5 mm, separated by 5 m distance. The annular output spot of fundamental mode with inner radius 4. 5 mm and outer radius 5.5 mm is obtained by the experiment. Therefore the feasibility of the scheme generating annular beam has been verified theoretically and experimentally.