Paper published in Nano Letters

Our paper on the dynamics of silison nanowires in optical tweezers has been published as A. Irrera et al, 'Photonic torque microscopy of the non-conservative force field for optically trapped silicon nanowires', Nano Letters 16, 4181-4188 (2016).

From the abstract: We measure, by photonic torque microscopy, the nonconservative rotational motion arising from the transverse components of the radiation pressure on optically trapped, ultrathin silicon nanowires. Unlike spherical particles, we find that nonconservative effects have a significant influence on the nanowire dynamics in the trap. We show that the extreme shape of the trapped nanowires yields a transverse component of the radiation pressure that results in an orbital rotation of the nanowire about the trap axis. We study the resulting motion as a function of optical power and nanowire length, discussing its size-scaling behavior. These shape-dependent nonconservative effects have implications for optical force calibration and optomechanics with levitated nonspherical particles.

New Group Members

This year we welcome two final year undergraduate students into the Optical Tweezers Group for their MSci projects.  Chris Richards will be working on light scattering calculations relevant to our optical trapping and optical binding experiments.  Zhi Wong will be investigating the optical and light scattering properties of metallic nanoparticles in his project on Plasmonics.

Optical trapping of porous silicon nanoparticles

Our paper Optical trapping of proous silicon nanoparticles has now been published as M. G. Donato et al, Nanotechnology 22 505704 (2011).

Abstract: Silicon nanoparticles obtained by ball-milling of a 50% porosity silicon layer have been optically trapped when dispersed in a water–surfactant environment. We measured the optical force constants using linearly and radially polarized trapping beams finding a reshaping of the optical potential and an enhanced axial spring constant for the latter. These measurements open perspectives for the control and handling of silicon nanoparticles as labeling agents in biological analysis and fluorescence imaging techniques.