Appl. Phys. Lett. 109, 191107 (2016); https://doi.org/10.1063/1.4967745
Conventional optical spanners based on free-space focused vortex beams are very difficult to manipulate subwavelength objects due to the diffraction limit, while optical subwavelength spanners are not explored. Evanescent wave is one potential tool to realize subwavelength trapping. By combining vortex with evanescent field, we find that the evanescent vortex can function as an optical subwavelength spanner. We investigate the factors that will affect the generation/function of this subwavelength spanner, including numerical aperture and topological charge. Further, by calculating the optical force and potential on the illuminated objects, we have demonstrated that the evanescent optical vortex field is able to trap 200 nm polystyrene spherical particles and to rotate them around the ring-shaped field at the same time, making it a subwavelength optical spanner. This mechanism can be used as a tool to study the behaviour of very small objects in physics and biology.
This research was supported by the National Research Foundation, Prime Minister's Office, Singapore under its Competitive Research Programme (CRP Award No. NRF-CRP10-2012-04). The work was also partially supported by Agency for Science, Technology and Research (A*STAR) under Grant Nos. 152-148-0031 and 152-700-0014.
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 109, 191107 (2016); and may be found at https://doi.org/10.1063/1.4967745