We propose the use of plasmonic nanorings
and nanotori for enhanced
colloidal photothermal energy conversion in the visible (vis) to near-infrared
(NIR) spectrum. We use full-wave field analysis to demonstrate for
the first time that the plasmon resonant absorption of these structures
remains high over a broad range of orientations relative to the polarization
of the incident field. The finding of strong orientation-independent
plasmon absorption is a key result as it indicates that the structures
can provide enhanced photothermal heating for colloidal applications.
We use computational fluid dynamic analysis to investigate pulsed-laser
plasmon-enhanced heating of the nanostructures in a fluid. We quantify
the laser intensity and pulse duration needed to superheat the nanostructures
to initiate bubble nucleation, and we simulate the dynamics of generated
nanobubbles. The modeling provides insight into the plasmonic and
thermofluidic behavior of colloidal nanostructures, thereby enabling
rational design of novel plasmon-enhanced photothermal processes.
A method is proposed for controlling optical polarization using metasurfaces formed from arrays of planar chiral-patterned dielectric metamolecules with embedded achiral plasmonic nanostructures. At plasmon resonance, the subwavelength plasmonic nanoinclusions induce enhanced polarization of the surrounding dielectric, which gives rise to rotation of the polarization azimuth in the transmitted field. Full-wave electromagnetic analysis is used to investigate the optical response of various proposed media as a function of the symmetry and spacing of the metamolecules. The analysis shows that the metamolecules can be tailored to control the polarization state of light and produce frequency selective giant rotation of the polarization azimuth exceeding 10 5 deg/mm in the visible to near-infrared spectrum with relatively low loss. The proposed method opens up opportunities for the development of versatile ultrathin media that can manipulate optical polarization for novel micro-optical applications.
We
study the photothermal behavior of laser-pulsed colloidal metallic
nanoframe structures using three-dimensional (3D) photonic and thermofluidic
computational models. The models predict the optical response of the
nanoframe, photothermal transduction at plasmon resonance, heat transfer
to the surrounding fluid, and the dynamics of nanobubble generation
under conditions of superheating. We quantify for the first time the
photothermal transduction of Au nanoframes as a function of their
orientation with respect to the polarization of the incident field
and, also, cooperative heating effects as a function of nanoframe
spacing. We further demonstrate that laser illumination parameters
and nanoframe properties can be tuned to control spatiotemporal heating
and nanobubble dynamics.
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