"Shape Matters: Optical Forces on Nanostructures"

Shape Matters: Optical Forces on Nanostructures

Dr. Onofrio M. Maragò

CNR-IPCF, Istituto per i Processi Chimico-Fisici,
F. Stagno D'Alcontres 37, 98158 Messina, Italy

Optical trapping (OT) of nanostructures has raised much interest in the last
few years. Manipulating nanoparticles with OT is generally difficult because
radiation forces scale approximately with particle volume and thermal
fluctuations can easily overwhelm trapping forces at the nanoscale. However,
carbon nanotubes, graphene, polymer nanofibers, plasmonic nanoparticles, and
semiconductor nanowires have now been stably trapped thanks either to their
highly anisotropic geometry or to their intrinsic resonant behavior. In
particular, OT has been used to build nano-assemblies, for ultra-sensitive
chemical-physical analysis of trapped nanostructures, as well as to
accurately measure forces with femtonewton resolution combining the
outstanding force-sensing capabilities of OT with increased nanometric
precision. In this context the role of shape is crucial for understanding
the interplay between optical forces and hydrodynamic interactions that
change dramatically with size, hence much affecting both force-sensing and
spatial resolution in precision applications.

In this seminar, after a general introduction on OT of nanostructures, I
show some results on optical force measurements and spectroscopy of linear
nanostructures (carbon nanotubes, silicon nanowires) and graphene. Thus, I
conclude with two novel concepts: i) intra-cavity optical trapping based on
optical feedback-locking, where the optical feedback on a diode laser source
is controlled by the light scattering from a trapped particle, and ii) laser
cooling of hybrid nanostructures that exhibit Fano resonances.

Date: April 15, 2013 (Monday)
Time: 15:40
Place: Physics Department Seminar Room (SA 240)