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Federal Research Center 
"Krasnoyarsk Science Center of the Siberian
Branch of the Russian Academy of Sciences"

 Федеральный исследовательский центр «Красноярский научный центр Сибирского отделения Российской академии наук»

Federal Research Center 
"Krasnoyarsk Science Center of the Siberian
Branch of the Russian Academy of Sciences"

Krasnoyarsk scientists have discovered the first evidence for the Talbot effect on fork-shaped gratings

6 March 2023 г. FRC KSC SB RAS

Красноярские ученые обнаружили первое свидетельство эффекта Тальбота на вилочковых решетках
Krasnoyarsk scientists have studied the behavior of light on fork-shaped gratings and for the first time observed there the manifestation of the Talbot effect. It is noteworthy that the effect manifests itself together with optical singularities. The obtained data aids in unraveling the wonderful world of near-field singular optics. The results of the study are published in the journal Annalen der Physik.

The optical Talbot effect is well known and it is observed in gratings with a strictly periodic structure. Its consists in the fact that when passing through a periodic grating, the light field is redistributed in space in such a way that in some places the light waves add up in phase and give the maximum light intensity, while in others, on the contrary, one observes the minima. The resulting spatial periodic structures are Talbot carpets. As a result, at certain distances behind the grating, images of the original periodic grating are formed, which are repeated many times at regular intervals.

Scientists of the Krasnoyarsk Science Center of SB RAS experimentally studied the diffraction of light on the fork-shaped gratings and for the first time discovered an optical phenomenon similar to the Talbot effect, which coexists in these structures with optical singularities.

Fork-shaped gratings are a special case of periodic gratings with a local violation of the periodicity. Their main feature is the possibility of obtaining arrays of optical vortices. Physicists considered the near-field diffraction by the fork-shaped grating by scanning the light field in the region behind the grating. As a result of light diffraction at this grating, there arises an ordered array of vortex optical beams at some distance from it, which is an analogue of the Talbot effect, that exists "in harmony" with optical singularities.

“Optical vortices are a unique physical object. They have special points - optical singularities, in which the phase has no definite value, and the intensity vanishes. Optical vortices have already found applications in high-resolution microscopy and optical tweezer devices. It was surprising to find that the optical singularities which appear behind a periodic grating do not destroy the regular field distributions, namely, the Talbot carpets, but only introduce distortions into them at the initial stages of propagation, that is, they "reshape" them, and then "hide" in the intensity minima in the Talbot planes. This indicates a symbiosis of optical singularities with the effect of self-healing of optical fields as a result of the Talbot effect,” said one of the authors of the research, Deputy Director for Science at the L.V. Kirensky Institute of Physics FRC KSC SB RAS, Andrey Vyunyshev.

The researchers note that the knowledge gained is of interest to fundamental science and provides better understanding of near-field singular optics.

“The study of the fundamental principle of the formation and propagation of optical vortices provides a deeper understanding of the physical nature behind the phenomena under consideration, which is of interest for the development of photonics,” emphasized the Head of the Laboratory of coherent optics at the L.V. Kirensky Institute of Physics SB RAS, Vasily Arkhipkin.

The research was carried out with the financial support of the Russian Science Foundation (No. 19-12-00203).


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