摘要:
抑制散射介质对光的散射,调控光在散射介质中的传输,是光通信、生物光子学、光镊等领域的重要课题.设计并实现了基于宽谱光源和数字相位共轭的可调控光在散射介质中传输的时间反演实验系统.实验获取了不同相干长度下物光和参考光束之间的光程差与干涉图样、相位图及时间反演信号之间的关系,分析了光源相干性对调控光在散射介质中传输的影响.实验结果表明,基于宽谱光源的相干特性和数字相位共轭技术,通过调节光程差能选择性获取同一散射角度及相同传输路径的光束的相对相位,再利用空间光调制器对参考光束进行调控,实现光束的反向传播,从而选择性实现对同一散射角度及相同传输路径的光的时间反演.
Abstract:
The strong light scattering in complex media, due to the highly inhomogeneous distributions of refractive indexes, is regarded as a fundamental impediment in numerous optical applications such as optical communications, biophotonics, and optical tweezer. Recently, many optical techniques based on the coherence of light source with long coherent length have been developed and widely used to suppress and control light scattering and propagation in complex media. Here, we propose and experimentally demonstrate the control and time reversal of only one part instead of all of light passing through complex media and different optical paths by combining digital phase conjugation and coherence gating based on partially coherent light source. Interference of reference and objective beams and corresponding phase maps are measured by the charge coupled device (CCD) and four-step phase-shift measuring technique only when the optical path difference between two beams is less than coherence length. Time reversal is achieved by spatial light modulator (SLM). In the experiment we further analyze the phase map and time reversal with different optical path differences and different coherence lengths of source. The experimental results demonstrate that for each optical path difference, the time reversal of only the part of light coming from the same scattering angle and identical optical path is achieved by digital phase conjugation and coherent gating of broadband light source.
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