Physicists at ITMO University have developed an optical tractor beam model to capture particles from new artificial materials. Such a beam is capable of moving particles or cells towards the radiation source. The study showed that hyperbolic metasurfaces are promising for experiments on the creation of tractor beam, as well as for its practical applications. The results are published in Photonics ACS.
Tractor bundles are familiar to many, thanks to the Star wars, Star Trek and countless representations of UFO abductions. However, scientists are trying to make such beams in reality and there are already many ways to move objects to a light source. Until now, however, these objects are represented by small particles and atoms instead of whole cows.
Researchers at the ITMO University have recently suggested using metamaterials to create such tractor spokes. Metamaterials are artificial periodic structures with unusual optical properties and repetitive features. For example, metamaterials can support hyperbolic modes: special states of the electromagnetic field appearing when the metamaterial interacts with light. Such states help control the optical forces that influence objects on the surface of the material and, ultimately, can help move particles to the light source.
"Our work is entirely devoted to the creation of tractors beams based on meta-surfaces as well as to the study of the physics that underlies them." We discovered that this effect appears because of the These modes act as an additional diffusion according to the law of conservation of the impulse, the particles can be moved in the direction of the light source. At the same time, the metamaterials present many other advantages over alternative methods of obtaining the tractor beam – more practical for practical use ", explains Alexander Shalin, head of the nano-optomechanics laboratory of the ITMO University.
In 2016, scientists from the ITMO University proposed another tractor beam model based on plasmonic resonance and the propagation of surface plasmon waves, oscillations of electron gas near the metal surface. The flat substrate allowed the researchers to work with the entire surface of the material instead of small areas, as in conventional plasmon tweezers. However, new work has shown that metamaterials based on flat structures that support the hyperbolic and plasmonic modes can become an even better base for tractor beams. Metasurfaces and metamaterials work with light throughout the range of visible wavelengths and help to better deal with energy losses. All this makes them promising for the experimental implementation of tractor beams.
"In future work, we plan to carry out experiments to get the tractor bundles, which is a necessary step towards the practical application of this phenomenon.In the near future, this technology will not help us to attract spaceships. and to remove cows, but can be used, for example, to create special traps for particles and cells or to perform chemical reactions selectively, "says Alexandra Ivinskaya, the first author of the article.
Trapping atoms, not spaceships, with bundles of tractors
Aliaksandra Ivinskaya et al. Optomechanical manipulation with hyperbolic metasurfaces, Photonics ACS (2018). DOI: 10.1021 / acsphotonics.8b00775