Seeing details of an object that are much smaller than the wavelength of illumination is commonly achieved via measurements of evanescent waves. Evanescent waves cannot propagate far and thus only exist very close to the object, such that these techniques are inevitably very invasive.
In a paper recently accepted for publication in Physical Review Letters, Philipp del Hougne (tenured CNRS researcher at IETR, Univ Rennes) and co-workers from Würzburg, Germany, and Paris, France, now unveil a mechanism to measure sub-wavelength information that operates without any manipulation in the object’s proximity. Instead, the researchers rely on ricocheting waves inside an irregular room. The longer the waves bounce around, the more often they encounter the object and the more sensitive they become to its sub-wavelength details. Because the ricocheting waves completely scramble the sought-after sub-wavelength information, the researchers trained an artificial-intelligence algorithm to decode their measurements.
The proposed approach to non-invasive sub-wavelength sensing meets the high-precision needs of emerging techniques for human-machine interactions which naturally deal with reverberating waves of different types. The reported microwave experiments achieve a resolution of 1/76th of the wavelength in a setting relevant to 6G communication that involves a reconfigurable intelligent surface and a software-defined radio. Further applications, including photo-acoustic imaging, are also envisioned.
Contact: Philipp del Hougne (philipp [dot] del-hougneuniv-rennes1 [dot] fr ; Website)
Reference: del Hougne, M., Gigan, S. and del Hougne, P. (2021). Deeply Sub-Wavelength Localization with Reverberation-Coded-Aperture. Physical Review Letters, in press.