Gain-Assisted Optomechanical Position Locking of Metal/Dielectric Nanoshells in Optical Potentials

We
investigate gain-assisted optical forces on dye-enriched silver
nanoshell in the quasi-static limit by means of a theoretical/numerical
approach. We demonstrate the onset of nonlinear optical trapping of
these resonant nanostructures in a counter-propagating Gaussian beam
configuration. We study the optical forces and trapping behavior as
a function of wavelength, particle gain level, and laser power. We
support the theoretical analysis with Brownian dynamics simulations
that show how particle position locking is achieved at high gains
in extended optical trapping potentials. Finally, for wavelengths
blue-detuned with respect to the plasmon-enhanced resonance, we observe
particle channeling by the standing wave antinodes due to gradient
force reversal. This work opens perspectives for gain-assisted optomechanics
where nonlinear optical forces are finely tuned to efficiently trap,
manipulate, channel, and deliver an externally controlled nanophotonic
system.