We study theoretically the opto-mechanics of a metallic nano-shell with a gain-enriched dielectric core in stationary Optical Tweezers. In order to avoid the counterproductive effects of scattering forces we choose a two counter-propagating beams configuration. The application of an external pump enhances the plasmonic resonance of the nano-shell thus affecting the optical forces acting on the particle even at pump powers below the emission threshold. We show that the trapping strength can be largely improved without the necessity to increase the trapping beam power. We support the theoretical analysis with Brownian dynamics simulations that show how particle position locking is achieved at high gains in exended 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.
We report on photo-thermal effects observed in gold nanoparticles (GNPs) dispersed in Nematic Liquid Crystals (NLCs). Under a suitable optical radiation, GNPs exhibit a strong light absorption/scattering; the effect depends on the refractive index of the medium surrounding the nanoparticles, which can be electrically or optically tuned. In this way, the system represents an ideal nano-source of heat, remotely controllable by light to adjust the temperature at the nanoscale. Photo-induced temperature variations in GNPs dispersed in NLCs have been investigated by implementing a theoretical model based on the thermal heating equation applied to an anisotropic medium; theoretical predictions have been compared with results of experiments carried out in a NLC medium hosting GNPs. Both theory and experiments represent a step forward to understand the physics of heat production at the nanoscale, with applications that range from photonics to nanomedicine.
The study of optical solitons and light filaments steering in liquid crystals requires utilization of particular
cells designed for top view investigation and realized with an input interface which enables both to control the
molecular director configuration and to prevent light scattering. Up to now, the director orientation imposed by
this additional interface has been only estimated by experimental observations. In this paper, we report on the
design and characterization of liquid crystal cells for investigation of optical spatial solitons as well as on a simple
model describing the configuration of the molecular director orientation under the anchoring action of multiple
interfaces. The model is based on the elastic continuum theory and only strong anchoring is considered for
boundary conditions. Controlling of the director orientation at the input interface, as well as in the bulk, allows
to obtain configurations that can produce distinct optical phenomena in a light beam propagating inside the cell.
For a particular director configuration, it is possible to produce two waves: the extraordinary and the ordinary
one. With a different director configuration, the extraordinary wave only is obtained, which propagates inside
the cell at an angle of more than 7° with respect to the impinging wave vector direction. Under this peculiar
configuration and by applying an external voltage, it is possible to have a good control of the propagation
direction of the optical spatial soliton.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.