Time-varying optical vortices enabled by time-modulated metasurfaces
In this paper, generation of optical vortices with time-varying orbital angular momentum (OAM) and topological charge is theoretically demonstrated based on time-modulated metasurfaces with a linearly azimuthal frequency gradient. The topological charge of such dynamic structured light beams is show...
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2020-07-01
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Online Access: | https://doi.org/10.1515/nanoph-2020-0202 |
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doaj-27e83682396f4cb9928988b5320a170c2021-09-06T19:20:35ZengDe GruyterNanophotonics2192-86062192-86142020-07-01992957297610.1515/nanoph-2020-0202Time-varying optical vortices enabled by time-modulated metasurfacesBarati Sedeh Hooman0Salary Mohammad Mahdi1Mosallaei Hossein2Metamaterials Lab, Electrical and Computer Engineering Department, Northeastern University, Boston, MA, 02115, USAMetamaterials Lab, Electrical and Computer Engineering Department, Northeastern University, Boston, MA, 02115, USAMetamaterials Lab, Electrical and Computer Engineering Department, Northeastern University, Boston, MA, 02115, USAIn this paper, generation of optical vortices with time-varying orbital angular momentum (OAM) and topological charge is theoretically demonstrated based on time-modulated metasurfaces with a linearly azimuthal frequency gradient. The topological charge of such dynamic structured light beams is shown to continuously and periodically change with time evolution while possessing a linear dependence on time and azimuthal frequency offset. The temporal variation of OAM yields a self-torqued beam exhibiting a continuous angular acceleration of light. The phenomenon is attributed to the azimuthal phase gradient in space-time generated by virtue of the spatiotemporal coherent path in the interference between different frequencies. In order to numerically authenticate this newly introduced concept, a reflective dielectric metasurface is modelled consisting of silicon nanodisk heterostructures integrated with indium-tin-oxide and gate dielectric layers on top of a mirror-backed silicon slab which renders an electrically tunable guided mode resonance mirror in near-infrared regime. The metasurface is divided into several azimuthal sections wherein nanodisk heterostructures are interconnected via nanobars serving as biasing lines. Addressing azimuthal sections with radio-frequency biasing signals of different frequencies, the direct dynamic photonic transitions of leaky-guided modes are leveraged for realization of an azimuthal frequency gradient in the optical field. Generation of dynamic twisted light beams with time-varying OAM by the metasurface is verified via performing several numerical simulations. Moreover, the role of modulation waveform and frequency gradient on the temporal evolution and diversity of generated optical vortices is investigated which offer a robust electrical control over the number of dynamic beams and their degree of self-torque. Our results point toward a new class of structured light for time-division multiple access in optical and quantum communication systems as well as unprecedented optomechanical manipulation of objects.https://doi.org/10.1515/nanoph-2020-0202orbital angular momentumoptical vortex beamtime-modulated metasurface |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Barati Sedeh Hooman Salary Mohammad Mahdi Mosallaei Hossein |
spellingShingle |
Barati Sedeh Hooman Salary Mohammad Mahdi Mosallaei Hossein Time-varying optical vortices enabled by time-modulated metasurfaces Nanophotonics orbital angular momentum optical vortex beam time-modulated metasurface |
author_facet |
Barati Sedeh Hooman Salary Mohammad Mahdi Mosallaei Hossein |
author_sort |
Barati Sedeh Hooman |
title |
Time-varying optical vortices enabled by time-modulated metasurfaces |
title_short |
Time-varying optical vortices enabled by time-modulated metasurfaces |
title_full |
Time-varying optical vortices enabled by time-modulated metasurfaces |
title_fullStr |
Time-varying optical vortices enabled by time-modulated metasurfaces |
title_full_unstemmed |
Time-varying optical vortices enabled by time-modulated metasurfaces |
title_sort |
time-varying optical vortices enabled by time-modulated metasurfaces |
publisher |
De Gruyter |
series |
Nanophotonics |
issn |
2192-8606 2192-8614 |
publishDate |
2020-07-01 |
description |
In this paper, generation of optical vortices with time-varying orbital angular momentum (OAM) and topological charge is theoretically demonstrated based on time-modulated metasurfaces with a linearly azimuthal frequency gradient. The topological charge of such dynamic structured light beams is shown to continuously and periodically change with time evolution while possessing a linear dependence on time and azimuthal frequency offset. The temporal variation of OAM yields a self-torqued beam exhibiting a continuous angular acceleration of light. The phenomenon is attributed to the azimuthal phase gradient in space-time generated by virtue of the spatiotemporal coherent path in the interference between different frequencies. In order to numerically authenticate this newly introduced concept, a reflective dielectric metasurface is modelled consisting of silicon nanodisk heterostructures integrated with indium-tin-oxide and gate dielectric layers on top of a mirror-backed silicon slab which renders an electrically tunable guided mode resonance mirror in near-infrared regime. The metasurface is divided into several azimuthal sections wherein nanodisk heterostructures are interconnected via nanobars serving as biasing lines. Addressing azimuthal sections with radio-frequency biasing signals of different frequencies, the direct dynamic photonic transitions of leaky-guided modes are leveraged for realization of an azimuthal frequency gradient in the optical field. Generation of dynamic twisted light beams with time-varying OAM by the metasurface is verified via performing several numerical simulations. Moreover, the role of modulation waveform and frequency gradient on the temporal evolution and diversity of generated optical vortices is investigated which offer a robust electrical control over the number of dynamic beams and their degree of self-torque. Our results point toward a new class of structured light for time-division multiple access in optical and quantum communication systems as well as unprecedented optomechanical manipulation of objects. |
topic |
orbital angular momentum optical vortex beam time-modulated metasurface |
url |
https://doi.org/10.1515/nanoph-2020-0202 |
work_keys_str_mv |
AT baratisedehhooman timevaryingopticalvorticesenabledbytimemodulatedmetasurfaces AT salarymohammadmahdi timevaryingopticalvorticesenabledbytimemodulatedmetasurfaces AT mosallaeihossein timevaryingopticalvorticesenabledbytimemodulatedmetasurfaces |
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