Light eddies with charges changing every 1/5 of a nanosecond are a phenomenon that has not been observed before. They can be useful in optical microscopy and quantum cryptography.
Scientists from the University of Iceland, the University of Southampton and the Skolkovo Institute of Science and Technology (Skoltech) have demonstrated the formation of a strange quantum phenomenon – a group of light vortices with periodic changes in charges. Details are described in the magazine physical review messages.
What are optical vortices?
Optical vortices are streams of light that are twisted like a vortex around the axis of their propagation. Swirls have the so-called topological charge, which can be understood as a number denoting the speed of its rotation and in what direction.
Scientists caused four vortices like the cluster and found that its charges change regularly with a period of 1/5 of a nanosecond. Such rapid oscillation of the charge has never been seen before.
There are high hopes for optical vortices because they offer the potential to overcome limitations in optical fiber throughput. They could also be useful in building optical tweezers – specially prepared lasers that are used to manipulate objects on a microscopic scale, for example atoms, nanoparticles, and even cells.
Standard optical vortices were produced in the Hybrid Photonics Laboratory at Skoltech, headed by Prof. Pavlos Lagodakis. The scientists used a semiconductor microcavity structure – two highly reflective mirrors with quantum wells in between. This allows the formation of quasiparticles called polaritons.
The goal was that we had to ensure that the charge of each vortex was initially random and that it would evolve freely according to the rules of intense quantum dynamics. This means that the system will automatically self-regulate its vortices, indicating an emerging behavior. So we couldn’t print the vortex lattice in our system with a laser, because that would create vortices with known charges and remove all spontaneity.Kirill Sitnik, PhD student at Skoltech, lead author of the work
We excited the polariton with a laser beam in the shape of a ring. At the critical excitation strength, some polaritons are localized within the optically induced efficient trap, occupying a superposition of the macroscopic quantum states with periodically oscillating self-assembled vortices.a. Pavlos Lagodakis
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