Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization
Plasmonic metasurfaces have been quite a fascinating framework to invoke transformation of incident electromagnetic waves for a while now. Oftentimes, the building block of these metasurfaces or the unit cells consists of two or more meta-resonators. As a consequence, near-field coupling amongst the...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | New Journal of Physics |
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| Online Access: | https://doi.org/10.1088/1367-2630/acd3a2 |
| _version_ | 1797748640752599040 |
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| author | Soumyajyoti Mallick Shreeya Rane Nityananda Acharyya Dibakar Roy Chowdhury |
| author_facet | Soumyajyoti Mallick Shreeya Rane Nityananda Acharyya Dibakar Roy Chowdhury |
| author_sort | Soumyajyoti Mallick |
| collection | DOAJ |
| description | Plasmonic metasurfaces have been quite a fascinating framework to invoke transformation of incident electromagnetic waves for a while now. Oftentimes, the building block of these metasurfaces or the unit cells consists of two or more meta-resonators. As a consequence, near-field coupling amongst these constituents may occur depending upon the spatial and spectral separation of the individual elements (meta-resonators). In such coupled structures resonance mode-hybridization can help in explaining the formation and energy re-distribution among the resonance modes. However, the coupling of these plasmonic modes is extremely sensitive to the polarization of the incident probe beam and offers ample amount of scope to harness newer physics. A qualitative understanding of the same can be attained through mode-hybridization phenomena. In this context, here, we have proposed a multi-element metastructure unit cell consisting of split ring and dipole resonators aiming to explore the intricate effects of the polarization dependency of these hybridized modes. Multi-resonator systems with varied inter-resonator spacing ( sp = 3.0, 5.0, and 7.0 μ m) are fabricated and characterized in the terahertz domain, showing a decrement in the frequency detuning ( δ ) by 30% (approx.) for a particular polarization orientation of THz probe beam. However, no such detuning is observed for the other orthogonal polarization configuration. Therefore, modulation of the resonance-hybridization is strongly dependent on the terahertz beam polarization. Further, as an outcome of the strong near-field coupling, the emergence of dual toroidal modes is observed. Excitation of toroidal modes demands thoughtful mode engineering to amplify the response of these otherwise feeble modes. Such modes are capable of strongly confining electromagnetic fields due to higher Quality (Q-) factor. Our experimental studies have shown significant signature of the presence of these modes in the Terahertz (THz) domain, backed up by rigorous numerical investigations along with multipole analysis. The calculated multipole decomposition demonstrates stronger scattering amplitude enhancements (∼7 times) at both the toroidal modes compared to off-resonant values. Such dual toroidal resonances are capable of superior field confinements as compared to single toroidal mode, and therefore, can potentially serve as an ideal testbed in developing next-generation multi-mode bio-sensors as well as realization of high Q-factor lasing cavities, electromagnetically induced transparency, non-radiating anapole modes, novel ultrafast switching, and several other applications. |
| first_indexed | 2024-03-12T16:08:38Z |
| format | Article |
| id | doaj.art-917c8bfa3f8e4338ac7f458ecaf73f75 |
| institution | Directory Open Access Journal |
| issn | 1367-2630 |
| language | English |
| last_indexed | 2024-03-12T16:08:38Z |
| publishDate | 2023-01-01 |
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| series | New Journal of Physics |
| spelling | doaj.art-917c8bfa3f8e4338ac7f458ecaf73f752023-08-09T14:15:38ZengIOP PublishingNew Journal of Physics1367-26302023-01-0125505301610.1088/1367-2630/acd3a2Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridizationSoumyajyoti Mallick0Shreeya Rane1https://orcid.org/0000-0002-6640-1929Nityananda Acharyya2Dibakar Roy Chowdhury3https://orcid.org/0000-0002-2129-0807Department of Physics, Mahindra University, Ecole Centrale School of Engineering , Hyderabad, IndiaDepartment of Physics, Mahindra University, Ecole Centrale School of Engineering , Hyderabad, IndiaDepartment of Physics, Mahindra University, Ecole Centrale School of Engineering , Hyderabad, IndiaDepartment of Physics, Mahindra University, Ecole Centrale School of Engineering , Hyderabad, IndiaPlasmonic metasurfaces have been quite a fascinating framework to invoke transformation of incident electromagnetic waves for a while now. Oftentimes, the building block of these metasurfaces or the unit cells consists of two or more meta-resonators. As a consequence, near-field coupling amongst these constituents may occur depending upon the spatial and spectral separation of the individual elements (meta-resonators). In such coupled structures resonance mode-hybridization can help in explaining the formation and energy re-distribution among the resonance modes. However, the coupling of these plasmonic modes is extremely sensitive to the polarization of the incident probe beam and offers ample amount of scope to harness newer physics. A qualitative understanding of the same can be attained through mode-hybridization phenomena. In this context, here, we have proposed a multi-element metastructure unit cell consisting of split ring and dipole resonators aiming to explore the intricate effects of the polarization dependency of these hybridized modes. Multi-resonator systems with varied inter-resonator spacing ( sp = 3.0, 5.0, and 7.0 μ m) are fabricated and characterized in the terahertz domain, showing a decrement in the frequency detuning ( δ ) by 30% (approx.) for a particular polarization orientation of THz probe beam. However, no such detuning is observed for the other orthogonal polarization configuration. Therefore, modulation of the resonance-hybridization is strongly dependent on the terahertz beam polarization. Further, as an outcome of the strong near-field coupling, the emergence of dual toroidal modes is observed. Excitation of toroidal modes demands thoughtful mode engineering to amplify the response of these otherwise feeble modes. Such modes are capable of strongly confining electromagnetic fields due to higher Quality (Q-) factor. Our experimental studies have shown significant signature of the presence of these modes in the Terahertz (THz) domain, backed up by rigorous numerical investigations along with multipole analysis. The calculated multipole decomposition demonstrates stronger scattering amplitude enhancements (∼7 times) at both the toroidal modes compared to off-resonant values. Such dual toroidal resonances are capable of superior field confinements as compared to single toroidal mode, and therefore, can potentially serve as an ideal testbed in developing next-generation multi-mode bio-sensors as well as realization of high Q-factor lasing cavities, electromagnetically induced transparency, non-radiating anapole modes, novel ultrafast switching, and several other applications.https://doi.org/10.1088/1367-2630/acd3a2terahertzplasmonicsmetasurfacestoroidal moments |
| spellingShingle | Soumyajyoti Mallick Shreeya Rane Nityananda Acharyya Dibakar Roy Chowdhury Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization New Journal of Physics terahertz plasmonics metasurfaces toroidal moments |
| title | Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization |
| title_full | Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization |
| title_fullStr | Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization |
| title_full_unstemmed | Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization |
| title_short | Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization |
| title_sort | accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization sensitive resonance hybridization |
| topic | terahertz plasmonics metasurfaces toroidal moments |
| url | https://doi.org/10.1088/1367-2630/acd3a2 |
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