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Detecting hidden objects through disorder

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By probing complex scattering systems with shaped light fields, it is now possible to detect hidden objects with exceptionally low photon fluxes.

In free space, it is easy to determine whether an object is present or not by measuring the light it scatters. However, whenever this object is surrounded by a complex scattering environment, this task becomes extremely challenging due to the absorption and multiple scattering processes that occur within the system. In a collaboration with Utrecht University (the Netherlands) and TU Wien (Austria), we have demonstrated theoretically and experimentally how to detect an object hidden inside a disordered complex system with an exceptionally low photon flux. This was achieved by successively identifying and generating probe fields that are specifically optimized for this purpose. Light is guided through the disorder in an optimal way, not only to strongly interact with the object, but also to be efficiently detected by the observer (see the attached figure).

These results show how to perform minimally-destructive measurements even in complex scattering systems, such as nano-structured processors or biological tissue. From a fundamental point of view, this work belongs to a line of research that aims at better understanding information transport in complex scattering media (on this subject, see also Nat. Phys. 17, 564-568, 2021, in which we demonstrated how to precisely estimate the value of a parameter despite the complexity of such media).

View online : D. Bouchet, L. M. Rachbauer, S. Rotter, A. P. Mosk, and E. Bossy, "Optimal control of coherent light scattering for binary decision problems", Physical Review Letters 127, 253902 (2021)