49,511 research outputs found
Thermal bistability through coupled photonic resonances
We present a scheme for achieving thermal bistability based on the selective
coupling of three optical resonances. This approach requires one of the
resonant frequencies to be temperature dependent, which can occur in materials
exhibiting strong thermo-optic effects. For illustration, we explore thermal
bistability in two different passive systems, involving either a periodic array
of Si ring resonators or parallel GaAs thin films separated by vacuum and
exchanging heat in the near field. Such a scheme could prove useful for thermal
memory devices operating with transition times hundreds of
milliseconds
Near-field thermal upconversion and energy transfer through a Kerr medium : Theory
We present an approach for achieving large Kerr --mediated
thermal energy transfer at the nanoscale that exploits a general coupled-mode
description of triply resonant, four-wave mixing processes. We analyze the
efficiency of thermal upconversion and energy transfer from mid- to
near-infrared wavelengths in planar geometries involving two slabs supporting
far-apart surface plasmon polaritons and separated by a nonlinear
medium that is irradiated by externally incident light. We study multiple
geometric and material configurations and different classes of interveening
mediums---either bulk or nanostructured lattices of nanoparticles embedded in
nonlinear materials---designed to resonantly enhance the interaction of the
incident light with thermal slab resonances. We find that even when the entire
system is in thermodynamic equilibrium (at room temperature) and under typical
drive intensities , the resulting upconversion
rates can approach and even exceed thermal flux rates achieved in typical
symmetric and non-equilibrium configurations of vacuum-separated slabs. The
proposed nonlinear scheme could potentially be exploited to achieve thermal
cooling and refrigeration at the nanoscale, and to actively control heat
transfer between materials with dramatically different resonant responses
Thermal radiation from optically driven Kerr () photonic cavities
We study thermal radiation from nonlinear () photonic cavities
coupled to external channels and subject to incident monochromatic light. Our
work extends related work on nonlinear mechanical oscillators [Phys. Rev. Lett.
97, 110602 (2006)] to the problem of thermal radiation, demonstrating that
bistability can enhance thermal radiation by orders of magnitude and result in
strong lineshape alternations, including "super-narrow spectral peaks"
occurring at the onset of kinetic phase transitions. We show that when the
cavities are designed so as to have perfect linear absorptivity (rate
matching), such thermally activated transitions can be exploited to
dramatically tune the output power and radiative properties of the cavity,
leading to a kind of Kerr-mediated thermo-optic effect. Finally, we demonstrate
that in certain parameter regimes, the output radiation exhibits Stokes and
anti-Stokes side peaks whose relative magnitudes can be altered by tuning the
internal temperature of the cavity relative to its surroundings, a consequence
of strong correlations and interference between the emitted and reflected
radiation
Near-field refrigeration and tunable heat exchange through four-wave mixing
We modify and extend a recently proposed four-wave mixing scheme [Opt.
Express 25 (19),23164 (2017)] for achieving near-field thermal upconversion and
energy transfer, to demonstrate efficient thermal refrigeration at low
intensities W/m over a wide range of gap sizes (from tens to
hundreds of nanometers) and operational temperatures (from tens to hundreds of
Kelvins). We further exploit the scheme to achieve magnitude and directional
tunability of near-field heat exchange between bodies held at different
temperatures
Temperature control of thermal radiation from heterogeneous bodies
We demonstrate that recent advances in nanoscale thermal transport and
temperature manipulation can be brought to bear on the problem of tailoring
thermal radiation from compact emitters. We show that wavelength-scale
composite bodies involving complicated arrangements of phase-change
chalcogenide (GST) glasses and metals or semiconductors can exhibit large
emissivities and partial directivities at mid-infrared wavelengths, a
consequence of temperature localization within the GST. We consider multiple
object topologies, including spherical, cylindrical, and mushroom-like
composites, and show that partial directivity follows from a complicated
interplay between particle shape, material dispersion, and temperature
localization. Our calculations exploit a recently developed fluctuating-volume
current formulation of electromagnetic fluctuations that rigorously captures
radiation phenomena in structures with both temperature and dielectric
inhomogeneities.Comment: 17 pages, 7 figuer
- …