Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering
Modulation of metasurfaces in time gives rise to several exotic space–time scattering phenomena by breaking the reciprocity constraint and generation of higher-order frequency harmonics. We introduce a new design paradigm for time-modulated metasurfaces, enabling tunable engineering of the generated...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2018-01-01
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| Series: | New Journal of Physics |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1367-2630/aaf47a |
| _version_ | 1797750208042369024 |
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| author | Mohammad Mahdi Salary Samad Jafar-Zanjani Hossein Mosallaei |
| author_facet | Mohammad Mahdi Salary Samad Jafar-Zanjani Hossein Mosallaei |
| author_sort | Mohammad Mahdi Salary |
| collection | DOAJ |
| description | Modulation of metasurfaces in time gives rise to several exotic space–time scattering phenomena by breaking the reciprocity constraint and generation of higher-order frequency harmonics. We introduce a new design paradigm for time-modulated metasurfaces, enabling tunable engineering of the generated frequency harmonics and their emerging wavefronts by electrically controlling the phase delay in modulation. It is demonstrated that the light acquires a dispersionless phase shift regardless of incident angle and polarization, upon undergoing frequency conversion in a time-modulated metasurface which is linearly proportional to the modulation phase delay and the order of generated frequency harmonic. The conversion efficiency to the frequency harmonics is independent of modulation phase delay and only depends on the modulation depth and resonant characteristics of the metasurface, with the highest efficiency occurring in the vicinity of resonance, and decreasing away from the resonant regime. The modulation-induced phase shift allows for creating tunable spatially varying phase discontinuities with 2 π span in the wavefronts of generated frequency harmonics for a wide range of frequencies and incident angles. Specifically, we apply this approach to a time-modulated metasurface in the Teraherz regime consisted of graphene-wrapped silicon microwires. For this purpose, we use an accurate and efficient semi-analytical framework based on multipole scattering. We demonstrate the utility of the design rule for tunable beam steering and focusing of generated frequency harmonics giving rise to several intriguing effects such as spatial decomposition of harmonics, anomalous bending with full coverage of angles and dual-polarity lensing. Furthermore, we investigate the angular and spectral performance of the time-modulated metasurface in manipulation of generated frequency harmonics to verify its constant phase response versus incident wavelength and angle. The nonreciprocal response of the metasurface in wavefront engineering is also studied by establishing nonreciprocal links with large isolations via modulation-induced phase shift. The proposed design approach enables a new class of high-efficiency tunable metasurfaces with wide angular and frequency bandwidth, wavefront engineering capabilities, nonreciprocal response and multi-functionality. |
| first_indexed | 2024-03-12T16:30:25Z |
| format | Article |
| id | doaj.art-4feadfb5ecf14054a806a22ed93a0136 |
| institution | Directory Open Access Journal |
| issn | 1367-2630 |
| language | English |
| last_indexed | 2024-03-12T16:30:25Z |
| publishDate | 2018-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | New Journal of Physics |
| spelling | doaj.art-4feadfb5ecf14054a806a22ed93a01362023-08-08T15:31:35ZengIOP PublishingNew Journal of Physics1367-26302018-01-01201212302310.1088/1367-2630/aaf47aElectrically tunable harmonics in time-modulated metasurfaces for wavefront engineeringMohammad Mahdi Salary0https://orcid.org/0000-0003-2056-3348Samad Jafar-Zanjani1Hossein Mosallaei2Metamaterial Laboratory, Electrical and Computer Engineering Department, Northeastern University , Boston, MA 02115, United States of AmericaMetamaterial Laboratory, Electrical and Computer Engineering Department, Northeastern University , Boston, MA 02115, United States of AmericaMetamaterial Laboratory, Electrical and Computer Engineering Department, Northeastern University , Boston, MA 02115, United States of AmericaModulation of metasurfaces in time gives rise to several exotic space–time scattering phenomena by breaking the reciprocity constraint and generation of higher-order frequency harmonics. We introduce a new design paradigm for time-modulated metasurfaces, enabling tunable engineering of the generated frequency harmonics and their emerging wavefronts by electrically controlling the phase delay in modulation. It is demonstrated that the light acquires a dispersionless phase shift regardless of incident angle and polarization, upon undergoing frequency conversion in a time-modulated metasurface which is linearly proportional to the modulation phase delay and the order of generated frequency harmonic. The conversion efficiency to the frequency harmonics is independent of modulation phase delay and only depends on the modulation depth and resonant characteristics of the metasurface, with the highest efficiency occurring in the vicinity of resonance, and decreasing away from the resonant regime. The modulation-induced phase shift allows for creating tunable spatially varying phase discontinuities with 2 π span in the wavefronts of generated frequency harmonics for a wide range of frequencies and incident angles. Specifically, we apply this approach to a time-modulated metasurface in the Teraherz regime consisted of graphene-wrapped silicon microwires. For this purpose, we use an accurate and efficient semi-analytical framework based on multipole scattering. We demonstrate the utility of the design rule for tunable beam steering and focusing of generated frequency harmonics giving rise to several intriguing effects such as spatial decomposition of harmonics, anomalous bending with full coverage of angles and dual-polarity lensing. Furthermore, we investigate the angular and spectral performance of the time-modulated metasurface in manipulation of generated frequency harmonics to verify its constant phase response versus incident wavelength and angle. The nonreciprocal response of the metasurface in wavefront engineering is also studied by establishing nonreciprocal links with large isolations via modulation-induced phase shift. The proposed design approach enables a new class of high-efficiency tunable metasurfaces with wide angular and frequency bandwidth, wavefront engineering capabilities, nonreciprocal response and multi-functionality.https://doi.org/10.1088/1367-2630/aaf47ametasurfacestime-modulationharmonic generationlight manipulationphase shiftnonreciprocity |
| spellingShingle | Mohammad Mahdi Salary Samad Jafar-Zanjani Hossein Mosallaei Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering New Journal of Physics metasurfaces time-modulation harmonic generation light manipulation phase shift nonreciprocity |
| title | Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering |
| title_full | Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering |
| title_fullStr | Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering |
| title_full_unstemmed | Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering |
| title_short | Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering |
| title_sort | electrically tunable harmonics in time modulated metasurfaces for wavefront engineering |
| topic | metasurfaces time-modulation harmonic generation light manipulation phase shift nonreciprocity |
| url | https://doi.org/10.1088/1367-2630/aaf47a |
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