Topological Charge of Multi-Color Optical Vortices
The topological charge of an optical vortex is a quantity rather stable against phase distortions, for example, turbulence. This makes the topological charge attractive for optical communications, but for many structured beams it is unknown. Here, we derive the topological charge (TC) of a coaxial s...
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-02-01
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| Series: | Photonics |
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| Online Access: | https://www.mdpi.com/2304-6732/9/3/145 |
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| author | Victor Victorovich Kotlyar Alexey Andreevich Kovalev Anton Gennadyevich Nalimov Sergey Sergeevich Stafeev |
| author_facet | Victor Victorovich Kotlyar Alexey Andreevich Kovalev Anton Gennadyevich Nalimov Sergey Sergeevich Stafeev |
| author_sort | Victor Victorovich Kotlyar |
| collection | DOAJ |
| description | The topological charge of an optical vortex is a quantity rather stable against phase distortions, for example, turbulence. This makes the topological charge attractive for optical communications, but for many structured beams it is unknown. Here, we derive the topological charge (TC) of a coaxial superposition of spatially coherent Laguerre–Gaussian beams with different colors, each beam with its own wavelength and its own TC. It turns out that the TC of such a superposition equals the TC of the LG beam with a longer wavelength, regardless of the weight coefficient of this beam in the superposition and regardless of its TC. It is interesting that the instantaneous TC of such a superposition is conserved on propagation, whereas the time-averaged intensity distribution of the colored optical vortex changes its gamut; if, in the near field, the colors of the light rings arrange along the radius according to their TCs in the superposition from lower to greater, then, on space propagation, the colors of the light rings in the cross-section are arranged in reverse order from the greater TC to the lower TC. We also demonstrate that, by choosing appropriate wavelengths (blue, green, and red) in a three-color superposition of single-ringed LG beams, it is possible to generate, at some propagation distance, a time-averaged light ring of the white color. If all the beams in a three-color superposition of single-ringed LG beams have the same TC, then there is a single ring of nearly white light in the initial plane. Then, on propagation in space, light rings of different colors acquire different radii: a smaller ring radius for a shorter wavelength. |
| first_indexed | 2024-03-09T12:56:53Z |
| format | Article |
| id | doaj.art-6324c45d9eff4e72a2b81f870ad2a66e |
| institution | Directory Open Access Journal |
| issn | 2304-6732 |
| language | English |
| last_indexed | 2024-03-09T12:56:53Z |
| publishDate | 2022-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Photonics |
| spelling | doaj.art-6324c45d9eff4e72a2b81f870ad2a66e2023-11-30T21:58:50ZengMDPI AGPhotonics2304-67322022-02-019314510.3390/photonics9030145Topological Charge of Multi-Color Optical VorticesVictor Victorovich Kotlyar0Alexey Andreevich Kovalev1Anton Gennadyevich Nalimov2Sergey Sergeevich Stafeev3Laser Measurements Laboratory, IPSI RAS—Branch of the FSRC “Crystallography and Photonics” RAS, Molodogvardeyskaya 151, 443001 Samara, RussiaLaser Measurements Laboratory, IPSI RAS—Branch of the FSRC “Crystallography and Photonics” RAS, Molodogvardeyskaya 151, 443001 Samara, RussiaLaser Measurements Laboratory, IPSI RAS—Branch of the FSRC “Crystallography and Photonics” RAS, Molodogvardeyskaya 151, 443001 Samara, RussiaLaser Measurements Laboratory, IPSI RAS—Branch of the FSRC “Crystallography and Photonics” RAS, Molodogvardeyskaya 151, 443001 Samara, RussiaThe topological charge of an optical vortex is a quantity rather stable against phase distortions, for example, turbulence. This makes the topological charge attractive for optical communications, but for many structured beams it is unknown. Here, we derive the topological charge (TC) of a coaxial superposition of spatially coherent Laguerre–Gaussian beams with different colors, each beam with its own wavelength and its own TC. It turns out that the TC of such a superposition equals the TC of the LG beam with a longer wavelength, regardless of the weight coefficient of this beam in the superposition and regardless of its TC. It is interesting that the instantaneous TC of such a superposition is conserved on propagation, whereas the time-averaged intensity distribution of the colored optical vortex changes its gamut; if, in the near field, the colors of the light rings arrange along the radius according to their TCs in the superposition from lower to greater, then, on space propagation, the colors of the light rings in the cross-section are arranged in reverse order from the greater TC to the lower TC. We also demonstrate that, by choosing appropriate wavelengths (blue, green, and red) in a three-color superposition of single-ringed LG beams, it is possible to generate, at some propagation distance, a time-averaged light ring of the white color. If all the beams in a three-color superposition of single-ringed LG beams have the same TC, then there is a single ring of nearly white light in the initial plane. Then, on propagation in space, light rings of different colors acquire different radii: a smaller ring radius for a shorter wavelength.https://www.mdpi.com/2304-6732/9/3/145coherent multi-color beamcolored beamwhite beamLaguerre–Gaussian beamoptical vortexphase singularity |
| spellingShingle | Victor Victorovich Kotlyar Alexey Andreevich Kovalev Anton Gennadyevich Nalimov Sergey Sergeevich Stafeev Topological Charge of Multi-Color Optical Vortices Photonics coherent multi-color beam colored beam white beam Laguerre–Gaussian beam optical vortex phase singularity |
| title | Topological Charge of Multi-Color Optical Vortices |
| title_full | Topological Charge of Multi-Color Optical Vortices |
| title_fullStr | Topological Charge of Multi-Color Optical Vortices |
| title_full_unstemmed | Topological Charge of Multi-Color Optical Vortices |
| title_short | Topological Charge of Multi-Color Optical Vortices |
| title_sort | topological charge of multi color optical vortices |
| topic | coherent multi-color beam colored beam white beam Laguerre–Gaussian beam optical vortex phase singularity |
| url | https://www.mdpi.com/2304-6732/9/3/145 |
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