物理学报2017，Vol.66Issue(11)：85-95,11.DOI:10.7498/aps.66.114202
四元裂解位相调制实现相干光通过散射介质聚焦
Four-element division algorithm for focusing light through scattering medium
摘要
Abstract
Light transport in complex disordered medium,such as white paint,milk,is a fundamental physical phenomenon,and it plays an important role in numerous applications including imaging through turbid layers,and quantum information processes.However,all spatial coherence is lost due to the distorted incident wavefront caused by repeated scattering and interference.Incident coherent light diffuses through the medium and cannot form a geometric focus but a volume speckle field on the imaging plane.In this paper,we propose a four-element division algorithm and experimentally demonstrate that using this algorithm to modulate the incident light,the shaped wavefront can focus through disordered material.At the beginning,we start with four segments on spatial light modulator (SLM),changing the phase of each segment from 0-2π to search for the optimal phase in terms of the maximal output intensity at a certain field.After the optimal phase of these four segments is found,each of all segments is divided further into four subsegments,so 16 subsegments are formed on the SLM.Just like the first step,the optimal phase is found by cycling the phases of these 16 subsegments.Sequentially,this procedure is repeated several times,so more and more subsegments are obtained.As a result,the modulated input light from SLM can be focused after it has passed through the turbid scattering medium.By employing this approach in the forward scattered experiment,the total pixels of spatial light modulator are divided into 4 4096 segments to shape the incident light.After separately searching for all the optimnal phase distributions,we can see that a sharp focusing is gradually achieved.Likewise,in backscattered experiment,4 1024 segments are used to focus the incident light after passing through the diffuse material.In comparison with stepwise sequential algorithm,the main advantage of our method is that the interference effect of all segments on SLM is taken into consideration,which means that the modulated and the modulating segments are connected with each other.In this way,the signal-to-noise ratio is higher and no iteration is needed.All this experiment shows that the four-element division algorithm can be employed to focus the incident light passing through a disorder material efficiently,which maybe provide a new idea and method in the field of biomedical imaging through scattering medium.关键词
散射介质/聚焦/相长干涉/四元裂解Key words
turbid medium/focusing/constructive interference/four-element division algorithm引用本文复制引用
张诚,方龙杰,朱建华,左浩毅,高福华,庞霖..四元裂解位相调制实现相干光通过散射介质聚焦[J].物理学报,2017,66(11):85-95,11.基金项目
Project supported by the National Natural Science Foundation of China (Grant Nos.61377054,61675140).国家自然科学基金(批准号:61377054,61675140)资助的课题. （Grant Nos.61377054,61675140）
