Optical manipulation of small particles has long been challenging mainly due to reduced gradient force. Rotation of particles by light is even more difficult since that requires the particle to be absorbing or to exhibit large polarizability and optical anisotropy. Otherwise, the optical field has to carry orbital angular momentum. Recently surface-plasmonenhanced optical near field has been used to effectively trap small particles. However, rotation and spinning of isotropic dielectric particles by light has not been demonstrated, not to mention a single device capable of multiple functions. Here, we report the first demonstration of selective trapping or rotation of isotropic dielectric micro-particles using one single plasmonic device, a plasmonic Archimedes spiral. Such functionality is of great interest and may find applications in various fields, such as protein folding analysis and local mixing in microfluidic channels.

Date Published: 16 September 2014
PDF: 6 pages
Proc. SPIE 9164, Optical Trapping and Optical Micromanipulation XI, 91643B (16 September 2014);

Published in SPIE Proceedings Vol. 9164:
Optical Trapping and Optical Micromanipulation XI
Kishan Dholakia; Gabriel C. Spalding, Editor(s)