2020 Fiscal Year Annual Research Report
Near-field polarization analysis for an optical nanofiber
| Project/Area Number |
18F18367
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| Research Institution | Okinawa Institute of Science and Technology Graduate University |
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Principal Investigator |
NICCHORMAIC SILE 沖縄科学技術大学院大学, 量子技術のための光・物質相互作用ユニット, 教授 (10715288)
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| Co-Investigator(Kenkyū-buntansha) |
TKACHENKO GEORGIY 沖縄科学技術大学院大学, 量子技術のための光・物質相互作用ユニット, 外国人特別研究員
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| Project Period (FY) |
2018-11-09 – 2021-03-31
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| Keywords | nanofiber / polarization / spin-orbit coupling / chiral |
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| Outline of Annual Research Achievements |
During the year, the polarization control in optical nanofibres has been further improved enabling studies on spin-orbit coupling for optically trapped chiral particles adjacent to an optical nanofibre. Spin angular momentum in electromagnetic waves is caused not only by field rotations associated with elliptical polarization, but also by spatial modulations of the field. Consequently, the spin carried by light does not have to be parallel to the energy transfer. Transverse components can be significant in strongly confined light, such as evanescent fields. Here, the transverse spin was revealed through its direct action on a probe particle held and spun by optical tweezers in the evanescent field at the surface of a nanofiber. The work has benefitted from a theoretical model developed by colleagues in ITMO, Russia. This work has been presented at several conferences (including OPIC 2021) and is being prepared for publication.
A second work has also been conducted building on the polarization control. Composite material objects such as Janus particles can exhibit interesting dynamics, such as propulsion in response to an external gradient field or collective assembly due to a generated localized thermal gradient around each particle. In this study, we demonstrated light-induced dynamics of metallo-dielectric Janus microspheres with a thin layer of gold that are trapped and propelled in the evanescent field of a nanofiber. We found that Janus particles with a 10 nm or 20 nm gold coating exhibit propulsion speed enhancements compared with uncoated silica microspheres.
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| Research Progress Status |
令和2年度が最終年度であるため、記入しない。
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| Strategy for Future Research Activity |
令和2年度が最終年度であるため、記入しない。
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