脉冲激光透过散射介质再聚焦及其影响因素

Laser Pulse Focusing through Turbid Media Based on Wavefront Shaping Technique

搭建了基于液晶空间光调制器和CCD反馈探测系统的相位补偿聚焦光路。通过双路信号发生器产生两路TTL信号分别触发控制CCD的开启和激光脉冲输出,调节两路信号之间的延时,实现了对目标区域光强信号的同步采集。通过自编的LabVIEW程序控制CCD光强信号读取和空间光调制器的随机相位图加载,组成一套闭环的自适应控制系统,通过遗传算法迭代搜寻最优化的补偿相位分布。利用空间光调制器加载这一最优化的相位分布,补偿散射介质导致的相位畸变,使得散射光束相位一致,在目标区域发生相长干涉,实现了散射光束的再聚焦。实验发现,激光输出模式和相干性对光场相位调控聚焦效果影响显著,利用腔内选模和空间滤波技术提高光源相干性后,聚焦效率显著提高,实现了光强增强因子为120倍的高质量散射光束再聚焦。

Light diffusion effect prevents light concentration and penetration in turbid media.Wavefront shaping technique has been adopted to compensate the wavefront distortion caused by light diffusion,and used to realize the laser pulse refocusing after passing through turbid media.The corresponding influence factors such as synchronization between the laser pulse and the CCD detector and laser source coherence have been studied.In order to optimize the pulse output and improve the laser coherence,we adopted intracavity mode-selection and spatial filtering technique and realized effective wavefront shaping and high efficiency light focusing through turbid media with an intensity enhancement factor of 120.