Browsing by Author "Cao, Hui"

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    Coherent enhancement of optical remission in diffusive media
    (National Academy of Sciences, 2022-10-03) Bender, Nicholas; Goetschy, Arthur; Hsu, Chia Wei; Yılmaz, Hasan; Palacios, Pablo Jara; Yamilov, Alexey; Cao, Hui
    Remitted waves are used for sensing and imaging in diverse diffusive media from the Earth’s crust to the human brain. Separating the source and detector increases the penetration depth of light, but the signal strength decreases rapidly, leading to a poor signal-to-noise ratio. Here, we show, experimentally and numerically, that wavefront shaping a laser beam incident on a diffusive sample enables an enhancement of remission by an order of magnitude at depths of up to 10 transport mean free paths. We develop a theoretical model which predicts the maximal remission enhancement. Our analysis reveals a significant improvement in the sensitivity of remitted waves to local changes of absorption deep inside diffusive media. This work illustrates the potential of coherent wavefront control for noninvasive diffuse wave imaging applications, such as diffuse optical tomography and functional near-infrared spectroscopy. Copyright © 2022 the Author(s). Published by PNAS.
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    Delivering broadband light deep inside diffusive media
    (NATURE PORTFOLIO, 2024-05-23) McIntosh, Rohin; Goetschy, Arthur; Bender, Nicholas; Yamilov, Alexey; Hsu, Chia Wei; Yılmaz, Hasan; Cao, Hui
    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. Owing to spectral long-range correlation, broadband energy can be delivered to extended targets deep inside a multiple-scattering system, greatly broadening the scope of controlling wave transport in disordered systems.
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    Multiregion light control in diffusive media via wavefront shaping
    (American Physical Society, 2024-10-02) Shaughnessy, Liam; McIntosh, Rohin E.; Goetschy, Arthur; Hsu, Chia Wei; Bender, Nicholas; Yılmaz, Hasan; Yamilov, Alexey; Cao, Hui
    Wavefront shaping allows focusing light through or inside strongly scattering media, but the background intensity also increases which reduces the target's contrast. By combining transmission or deposition matrices for different regions, we construct joint operators to achieve spatially resolved control of light in diffusive systems. The eigenmode of a contrast operator can maximize the power contrast between a target and its surrounding. A difference operator enhances the power delivery to a target while avoiding the background increase. This work opens the door to coherent control of nonlocal effects in wave transport for practical applications.
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    Roadmap on wavefront shaping and deep imaging in complex media
    (Institute of Physics, 2022-10) Gigan, Sylvain; Katz, Ori; De Aguiar, Hilton B.; Andresen, Esben Ravn; Aubry, Alexandre; Bertolotti, Jacopo; Bossy, Emmanuel; Bouchet, Dorian; Brake, Joshua; Brasselet, Sophie; Bromberg, Yaron; Cao, Hui; Chaigne, Thomas; Cheng, Zhongtao; Choi, Wonshik; Čižmár, Tomáš; Cui, Meng; Curtis, Vincent R.; Defienne, Hugo; Hofer, Matthias; Horisaki, Ryoichi; Horstmeyer, Roarke; Ji, Na; LaViolette, Aaron K.; Mertz, Jerome; Moser, Christophe; Mosk, Allard P; Pégard, Nicolas C; Piestun, Rafael; Popoff, Sebastien; Phillips, David B.; Psaltis, Demetri; Rahmani, Babak; Rigneault, Hervé; Rotter, Stefan; Tian, Lei; Vellekoop, Ivo M.; Waller, Laura; Wang, Lihong; Weber, Timothy; Xiao, Sheng; Xu, Chris; Yamilov, Alexey; Yang, Changhuei; Yılmaz, Hasan
    The last decade has seen the development of a wide set of tools, such as wavefront shaping, computational or fundamental methods, that allow us to understand and control light propagation in a complex medium, such as biological tissues or multimode fibers. A vibrant and diverse community is now working in this field, which has revolutionized the prospect of diffraction-limited imaging at depth in tissues. This roadmap highlights several key aspects of this fast developing field, and some of the challenges and opportunities ahead. © 2022 The Author(s). Published by IOP Publishing Ltd.