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Focusing of light energy inside a scattering medium by controlling the time-gated multiple light scattering


The efficient delivery of light energy is a prerequisite for the non-invasive imaging and stimulating of target objects embedded deep within a scattering medium. However, the injected waves experience random diffusion by multiple light scattering, and only a small fraction reaches the target object. Here, we present a method to counteract wave diffusion and to focus multiple-scattered waves at the deeply embedded target. To realize this, we experimentally inject light into the reflection eigenchannels of a specific flight time to preferably enhance the intensity of those multiple-scattered waves that have interacted with the target object. For targets that are too deep to be visible by optical imaging, we demonstrate a more than tenfold enhancement in light energy delivery in comparison with ordinary wave diffusion cases. This work will lay a foundation to enhance the working depth of imaging, sensing and light stimulation.

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Fig. 1: Wave propagation within scattering media.
Fig. 2: Analyses of coupling light to the time-gated eigenchannels.
Fig. 3: Experimental coupling of light to time-gated reflection eigenchannels.
Fig. 4: Reflection and transmission images of time-gated reflection eigenchannels.
Fig. 5: Demonstration of enhanced light energy delivery through a rat skull.


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This research was supported by IBS-R023-D1 and the Global Frontier Program (2014M3A6B3063710) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning. It was also supported by the Korea Health Technology R&D Project (HI14C0748) funded by the Ministry of Health & Welfare, Republic of Korea. H.-G.P. acknowledges support from an NRF grant funded by the Korean government (MSIT) (no. 2009-0081565).

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Authors and Affiliations



Wonshik C., S.J., S.K. and Y.-R.L. conceived the experiment, and S.J. carried out the measurements. Experimental data were analysed by S.J., Y.-R.L. and Wonshik C. Y.-R.L. developed the theoretical framework and analysed FDTD simulation results with Wonshik C. Wonjun C. constructed the FDTD platform for computing the time-resolved reflection matrix and its eigenchannels, and ran the FDTD simulations. Y.-S.L. assisted in the design of the optical set-up. J.H.H. prepared biological tissues. J.-S.P. and H.-G.P. provided silver disks. S.J., Y.-R.L. and Wonshik C. prepared the manuscript. All authors contributed to finalizing the manuscript.

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Correspondence to Wonshik Choi.

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Supplementary Information

Numerical and theoretical analyses, additional experimental data analysis, comparison of experimental data with the theoretical results, and further discussion on the proposed method.

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Jeong, S., Lee, YR., Choi, W. et al. Focusing of light energy inside a scattering medium by controlling the time-gated multiple light scattering. Nature Photon 12, 277–283 (2018).

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