Optimal blind focusing on perturbation-inducing targets in sub-unitary complex media

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Hauptverfasser: Sol, Jérôme, Magoarou, Luc Le, del Hougne, Philipp
Format: Preprint
Veröffentlicht: 2024
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author Sol, Jérôme
Magoarou, Luc Le
del Hougne, Philipp
author_facet Sol, Jérôme
Magoarou, Luc Le
del Hougne, Philipp
contents The scattering of waves in a complex medium is perturbed by polarizability changes or motion of embedded targets. These perturbations could serve as perfectly non-invasive guidestars for focusing on the targets. In this Letter, we theoretically derive a fundamental difference between these two perturbation types (the change of the scattering matrix is of rank one [two] for target polarizability changes [motion]) and identify accordingly optimal strategies to perfectly focus on the target in both cases. For target motion, at least two displacements are necessary. Furthermore, for the case of dynamic complex media additionally featuring parasitic perturbers, we establish a non-invasive scheme to achieve optimal time-averaged power delivery to a perturbation-inducing target. In all cases, no assumptions about the unitarity of the system's scattering matrix or the size of the perturbation are necessary. We experimentally demonstrate all results in the microwave regime using a strongly sub-unitary lossy chaotic cavity as complex medium. Our experiments highlight that the target's "structural scattering" is irrelevant [must be negligible] in the case of target polarizability changes [motion]. We expect our results to find applications in communications, cybersecurity, bioelectronics, flow-cytometry and self-propelled nano-swimmers.
format Preprint
id arxiv_https___arxiv_org_abs_2401_15415
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Optimal blind focusing on perturbation-inducing targets in sub-unitary complex media
Sol, Jérôme
Magoarou, Luc Le
del Hougne, Philipp
Optics
Signal Processing
Applied Physics
The scattering of waves in a complex medium is perturbed by polarizability changes or motion of embedded targets. These perturbations could serve as perfectly non-invasive guidestars for focusing on the targets. In this Letter, we theoretically derive a fundamental difference between these two perturbation types (the change of the scattering matrix is of rank one [two] for target polarizability changes [motion]) and identify accordingly optimal strategies to perfectly focus on the target in both cases. For target motion, at least two displacements are necessary. Furthermore, for the case of dynamic complex media additionally featuring parasitic perturbers, we establish a non-invasive scheme to achieve optimal time-averaged power delivery to a perturbation-inducing target. In all cases, no assumptions about the unitarity of the system's scattering matrix or the size of the perturbation are necessary. We experimentally demonstrate all results in the microwave regime using a strongly sub-unitary lossy chaotic cavity as complex medium. Our experiments highlight that the target's "structural scattering" is irrelevant [must be negligible] in the case of target polarizability changes [motion]. We expect our results to find applications in communications, cybersecurity, bioelectronics, flow-cytometry and self-propelled nano-swimmers.
title Optimal blind focusing on perturbation-inducing targets in sub-unitary complex media
topic Optics
Signal Processing
Applied Physics
url https://arxiv.org/abs/2401.15415