Transverse optical torque observed at the nanoscale

Nature Physics (2026)Cite this article Optical forces and torques acting on resonant nanostructures smaller than the wavelength of light have attracted interest in nanoscience and nanotechnology. However, experimental characterization at the nanoscale remains challenging due to the diffraction limit of light. Here we present an approach for the three-dimensional measurement of nanoscale optical forces and torques. This is achieved through the optical trapping and precision spatial tracking of a designed microscale structure that contains embedded target nanostructures. Our method enables the confinement and measurement of nanostructure positions and orientations across three translational and three rotational degrees of freedom, independent of the size, shape and material of the nanostructure. Using this method, we observe transverse optical torque on plasmon-resonant nanostructures and reveal that this behaviour is governed by the optical helicity rather than the angular momentum of incident light. This versatile platform advances our fundamental understanding of nano-optomechanical interactions and opens up possibilities for precise optical manipulation and nanoactuator design.This is a preview of subscription content, access via your institution Access Nature and 54 other Nature Portfolio journals Get Nature+, our best-value online-access subscription $32.99 / 30 days cancel any timeSubscribe to this journal Receive 12 print issues and online access $259.00 per yearonly $21.58 per issueBuy this articleUSD 39.95Prices may be subject to local taxes which are calculated during checkoutSource data are provided with the paper. 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Phys. 101, 023106 (2007).Article ADS Google Scholar Download referencesThis work was supported by Grants-in-Aid for Scientific Research (KAKENHI) (number JP22H05132 in Transformative Research Areas (A) ‘Chiral materials science pioneered by the helicity of light’ and number JP21K14594 to Y.Y.T.) and program for Forming Japan’s Peak Research Universities (J-PEAKS) (number JPJS00420230001 to Y.Y.T.) from the Japan Society for the Promotion of Science (JSPS), and JST FOREST Program (number JPMJFR213O to Y.Y.T.).Institute of Industrial Science, University of Tokyo, Tokyo, JapanRyoma Fukuhara, Tsutomu Shimura & Yoshito Y. TanakaLaboratory of Nanosystem Optical Manipulation, Department of Photonics and Optical Science, Research Institute for Electronic Science, Hokkaido University, Sapporo, JapanYoshito Y. TanakaSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarY.Y.T. conceived and designed the research project. R.F. and Y.Y.T. performed the sample fabrication. R.F. and Y.Y.T. performed the calculations and established the experimental setup. R.F. and Y.Y.T. analysed the data, with T.S. contributing to the discussions and analysis. R.F. and Y.Y.T. wrote the manuscript with input from all authors.Correspondence to Yoshito Y. Tanaka.The authors declare no competing interests.Nature Physics thanks the anonymous reviewers for their contribution to the peer review of this work. Peer reviewer reports are available.Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Supplementary Notes 1–4 and Figs. 1–12.Optical trapping of a micro-platform in water under bright-field illumination. The micro-platform consists of a central body with an embedded target nanostructure and four arms with embedded nanodiscs (Supplementary Fig. 1). The contours of the micro-platform are clearly visible due to the refractive index difference between the micro-platform and water.Optical trapping of a solvent- and index-matched micro-platform under dark-field illumination. The bright spots at the four corners represent optically trapped nanodiscs, whose 3D positions were measured using an astigmatic particle-tracking method. The weak bright spot in the centre indicates a single V-shaped nanostructure. Another bright spot near the spot in the top-left corner was used to roughly identify the orientation of the V structure. The refractive index of the solvent was matched to that of the micro-platform to prevent optical force and torque generation from light reflection and refraction at the micro-platform surface, which would otherwise drastically reduce the signal-to-noise ratio in the measurement of optical force and torque acting on the target nanostructure.Statistical source data.Statistical source data.Statistical source data.Statistical source data.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.Reprints and permissionsFukuhara, R., Shimura, T. & Tanaka, Y.Y. Transverse optical torque observed at the nanoscale. Nat. Phys. (2026). https://doi.org/10.1038/s41567-026-03268-6Download citationReceived: 02 May 2025Accepted: 25 March 2026Published: 20 April 2026Version of record: 20 April 2026DOI: https://doi.org/10.1038/s41567-026-03268-6Anyone you share the following link with will be able to read this content:Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative