单涡旋场激光传输特性研究

Research on Laser Transmission Characteristic with Single Vortex

对单涡旋场激光传输特性进行了研究。用积分方程形式将整个流场分解成体元,每个体元中的折射率分布不均匀,用麦克斯韦积分方程替代微分方程求解整个流场的光场分布,给出了气动涡流折射率场的计算模型。当流场只存在一个理想涡流且涡流的折射率场有近似的解析形式时,基于非均匀介质散射理论,用Rytov散射近似,由积分方程计算观测平面上光场所受的流场扰动。讨论了不同激光传输距离下流场扰动时的光场空间强度分布。结果发现:随着激光传输距离的增加,光强急剧下降,中心位置光强与无流场扰动时自由空间高斯光束传输中心位置光强相近,但在两侧会形成一个暗环,使激光光场的空间强度分布发生改变,导致激光脉冲光束出现形变。研究说明了用积分方程描述气动光学效应的可行性,为精确计算复杂涡结构流场提供了一种新思路。

The laser transmission characteristic with single vortex was studied in this paper.The whole flow field was broken down into several individual units and the refractive index of each unit was uneven.The Maxwell integral equation was used to replace differential equation to solve the flow field of the optical field distribution.The computation model of the refractive index of pneumatics vortex was given out.When there was only one ideal vortex flow field and eddy current of refractive index had approximate analytic form,the integral equation was used to calculate the flow filed disturbance by Rytov scatter approximate based on scattering theory of non-uniform medum scattering tueory.The spatial intensity distribution of light field within disturbance under various laser transmission distance was discussed.It was found that the light intensity would decrease greatly as the distance increasing,and the light intensity at centre was similar to the one of free spatial Gauss beam transmission at centre without disturbance but a dark ring would be formed at both sides which could make spatial light distribution of laser field changed and result in deformation of laser pulse beam.The study demonstrated that the integral equation was used to describe pneumatic optical effect was feasible,and it provided a new way for the precise calculation of complex vortex field structure.