Publication in Nature Communications

18.1. 2019 09:09 What is going on

Publication of Transverse spin forces and non-equilibrium particle dynamics in a circularly polarized vacuum optical trap in Nature Communications.

** Spinning Light **

Anyone who has ever played tennis or football soon found out that the rotating ball (s) is flying over completely unexpected tracks. This rotation of the object around its own axis can occur in the wild and in the laboratory in an unexpected way, from the rotation of the Earth by the riverbed to the possibility of detecting tumors in the brain by means of magnetic resonance based on the rotation of the atomic nuclei. Similarly, light particles – photons can behave. For many years, it has been known that light can act with noticeable force on very small objects (with a diameter from tens of nanometers to a tenth of a millimeter) and trap them in a light trap. Last year, half of the Nobel Prize for Physics was awarded to 96-year-old Arthur Ashkin, who demonstrated this principle of so-called optical tweezers and successfully exploited them, especially in biology. Recent advanced experiments conducted at the Institute of Instrumentation of the Academy of Sciences of the Czech Republic in Brno have shown that the use of photons with their own rotation (the so-called circularly polarized light) results in dramatically different behavior of the particles captured in the optical tweezers.

In their experiments, scientists have created a light trap in a vacuum where there is much less resistance to the environment, and objects can move much faster. Since Arthur Ashkin's first experiments, it is known that when photons are captured using photons without their own rotation, particles in the trap will be held more strongly in the vicinity of the light trap if we increase the number of photons. But scientists from Brno used photons with their own rotation and found the opposite behavior. The particle does not remain in the light trap, but tends to circle around it in orbit, the radius of which increases with the increasing number of photons. The difficult-to-use self-rotation of photons is thus transformed into cyclic mechanical motion of the particle. This work was recently published in the prestigious Nature Communications magazine and responds to deep questions about light diffusion and opens up new experimental paths to light-powered micromotors or new, more sensitive sensors.

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