Optical torque from enhanced scattering by multipolar plasmonic resonance
We present a theoretical study of the optical angular momentum transfer from a circularly polarized plane wave to thin metal nanoparticles of different rotational symmetries. While absorption has been regarded as the predominant mechanism of torque generation on the nanoscale, we demonstrate numeric...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | en_US |
| Published: |
Walter de Gruyter
2015
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| Online Access: | http://hdl.handle.net/1721.1/97432 https://orcid.org/0000-0003-0501-8843 https://orcid.org/0000-0002-9813-2401 https://orcid.org/0000-0001-6386-5878 https://orcid.org/0000-0001-5713-629X |
| Summary: | We present a theoretical study of the optical angular momentum transfer from a circularly polarized plane wave to thin metal nanoparticles of different rotational symmetries. While absorption has been regarded as the predominant mechanism of torque generation on the nanoscale, we demonstrate numerically how the contribution from scattering can be enhanced by using multipolar plasmon resonance. The multipolar modes in non-circular particles can convert the angular momentum carried by the scattered field and thereby produce scattering-dominant optical torque, while a circularly symmetric particle cannot. Our results show that the optical torque induced by resonant scattering can contribute to 80% of the total optical torque in gold particles. This scattering-dominant torque generation is extremely mode-specific, and deserves to be distinguished from the absorption-dominant mechanism. Our findings might have applications in optical manipulation on the nanoscale as well as new designs in plasmonics and metamaterials. |
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