Liu Wei, Zhou Zhihao, Chen Lei, Luo Xin, Liu Yuehan, Chen Xianfeng, Wan Wenjie
Opt Express. 2021 Sep 13;29(19):29972-29981. doi: 10.1364/OE.433513.
Imaging through a dynamical opaque scattering medium is an almost impossible task, where strong multiple light scattering from moving scatters dynamically prevents imaging formations even with state-of-art techniques like correlation imaging or adaptive optics. Meanwhile, a small number of ballistic photons can still penetrate through but require demanding detection in terms of a ultrashort time gate and high sensitivity. However, visible light is strongly scattered for most of scattering media. Here we experimentally demonstrate a non-invasive coherent imaging scheme based on two-photon absorption capable of imaging through dynamical scattering media with a length equivalent to 28 times mean free paths for single photon transport, where two-photon absorption in a conventional semiconductor photodetector when phase matching is not required works over a wide bandwidth so it can support a fast time gate down to femtosecond level, short enough to distinguish ballistic photons from scattering background, and allows accessing longer wavelengths for deeper penetration. This technique combined with successful optical coherence tomography may pave a new way for imaging through fog, storm, and rain as well as biomedical imaging applications.
通过动态不透明散射介质进行成像几乎是一项不可能完成的任务，因为运动散射体产生的强烈多重光散射会动态地阻碍成像的形成，即便使用相关成像或自适应光学等先进技术也无济于事。与此同时，仍有少量弹道光子能够穿透介质，但这需要在超短时间门控和高灵敏度方面进行严格检测。然而，对于大多数散射介质而言，可见光会被强烈散射。在此，我们通过实验展示了一种基于双光子吸收的非侵入式相干成像方案，该方案能够透过长度相当于单光子传输平均自由程28倍的动态散射介质进行成像。在不需要相位匹配的情况下，传统半导体光电探测器中的双光子吸收在很宽的带宽范围内都能起作用，因此它可以支持低至飞秒级的快速时间门控，短到足以将弹道光子与散射背景区分开来，并且能够使用更长波长以实现更深的穿透。这项技术与成功的光学相干断层扫描相结合，可能会为透过雾、暴风雨和雨进行成像以及生物医学成像应用开辟一条新途径。
