New technique could revolutionize invisibility cloaks

Researchers from the Universitat Politècnica de València (UPV), in collaboration with the Nanophotonics Technology Center (NTC) and the company DAS Photonics, have introduced a groundbreaking approach to the design of invisibility cloaks. Rather than focusing on maximizing invisibility, their study proposes the use of diffraction tomography techniques to detect these cloaking devices. Published in the journal Laser & Photonics Reviews, their work aims to revolutionize the field.

Traditionally, efforts in invisibility science have concentrated on creating practical cloak designs and enhancing their efficiency. However, the Valencian researchers believe that detecting these cloaks deserves equal attention. By employing diffraction tomography, they aim to redesign invisibility cloaks to make their detection significantly easier.

Carlos García Meca, Research Director at DAS Photonics, explains the implications of their study. The proposed technique not only promises to improve the detection of invisibility devices but also offers various applications across different fields. For instance, it could ensure the effective use of the electromagnetic spectrum to identify the presence of hostile agents, even when they employ countermeasures to avoid detection. As an example, García Meca mentions a soldier using an invisibility cloak to hide a small observation post and evade standard detection methods. The developed technique would enable the identification of such individuals.

Much more information thanks to tomography

The current evaluation of invisibility cloaks relies solely on measuring the total energy re-emitted by the cloak when illuminated. Fran Díaz, a researcher at the UPV’s Nanophotonic Technology Centre, explains that the performance of a cloak is determined by estimating the re-emitted energy in all possible directions. If the energy re-emitted is low, the cloak is considered effective; if it is high, the object being hidden is not rendered invisible.

In contrast, the proposal put forward by the NTC-DAS team offers a more comprehensive analysis of cloak layers. By employing tomography and utilizing different illumination angles, this technique extracts valuable information such as phase and scattered field distribution. Consequently, a map of the object’s refractive index is obtained, significantly enhancing detection sensitivity and enabling imaging of the invisibility cloaks themselves, including their size and shape. As a result, the cloaks become more easily detectable, eroding their true invisibility.

The Valencian researchers suggest that this method could also be extended to the detection of acoustic invisibility cloaks. Their work conducted at the Nanophotonics Technology Centre of the Universitat Politècnica de València, in collaboration with DAS Photonics, has been featured on the inside cover of Laser & Photonics Reviews.

In summary, the proposed technique revolutionizes the evaluation of invisibility cloaks by utilizing tomography to extract detailed information about their layers. This approach not only improves detection sensitivity but also enables the imaging of cloaks, making them less invisible. The method shows promise for detecting acoustic invisibility cloaks as well.

More applications in electronic warfare and biomedical imaging

The introduction of diffraction tomography as a means to evaluate invisibility cloaks signifies a significant advancement, establishing a novel design and characterization standard for these devices. This new detection technique is more rigorous, placing higher demands on cloak performance assessment.

The implications of this breakthrough extend across various domains, ranging from fundamental progress in the field of invisibility science to practical applications in signal intelligence, electronic warfare, and even biomedical imaging. The collaborative study by DAS Photonics and UPV researchers suggests that invisibility layers utilizing “scatter cancellation” could be employed to enhance the resolution of tomographic techniques when imaging clusters of small particles.

By expanding the possibilities for cloak design and incorporating advanced characterization methods, this research sets the stage for future advancements in the field. The newfound understanding of cloak performance and the potential application of scatter cancellation layers hold promise for a wide range of applications, making significant contributions to fields such as telecommunications, defense, and medical imaging.

Source: Universitat Politècnica de València

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