近日，美国耶鲁大学的Hui Cao及其研究团队取得一项新进展。经过不懈努力，他们实现在扩散介质深处传输宽带光。相关研究成果已于2024年5月23日在国际知名学术期刊《自然—光子学》上发表。

该研究团队引入了一种宽带沉积矩阵，该矩阵可以识别单个输入波前，从而最大限度地提高传输到扩散系统深处扩展目标的宽带能量。实验证实，即便在相干时间远小于光在散射样品中扩散停留时间的情况下，对于包含1,700个散斑颗粒且位于10个传输平均自由程深度的目标，长程空间和光谱相关性依然能带来高达六倍的能量增强。

值得注意的是，在宽带（快速退相干）极限条件下，这种能量传输的增强几乎不受目标深度和耗散的影响。此项研究通过结合数值模拟和理论分析，成功确立了宽带能量传输深入扩散系统的基本极限，这一发现对于实际应用具有重要的指导意义。

据悉，波前整形可以通过散射波的建设性干涉，将相干光定向传输到随机散射介质中，如生物组织。然而，宽带波具有较短的相干时间，削弱了干涉效应。

附：英文原文

Title: Delivering broadband light deep inside diffusive media

Author: McIntosh, Rohin, Goetschy, Arthur, Bender, Nicholas, Yamilov, Alexey, Hsu, Chia Wei, Ylmaz, Hasan, Cao, Hui

Issue&Volume: 2024-05-23

Abstract: Wavefront shaping enables the targeted delivery of coherent light into random-scattering media, such as biological tissue, by the constructive interference of scattered waves. However, broadband waves have short coherence times, weakening the interference effect. Here we introduce a broadband deposition matrix that identifies a single input wavefront that maximizes the broadband energy delivered to an extended target deep inside a diffusive system. We experimentally demonstrate that long-range spatial and spectral correlations result in sixfold energy enhancement for targets containing 1,700 speckle grains and located at a depth of up to ten transport mean free paths, even when the coherence time is an order of magnitude shorter than the diffusion dwell time of light in the scattering sample. In the broadband (fast decoherence) limit, enhancement of energy delivery to extended targets becomes nearly independent of the target depth and dissipation. Our experiments, numerical simulations and analytic theory establish the fundamental limit for broadband energy delivery deep into a diffusive system, which has important consequences for practical applications.

DOI: 10.1038/s41566-024-01446-7

Source: https://www.nature.com/articles/s41566-024-01446-7