148 research outputs found
Modulation of near-field heat transfer between two gratings
We present a theoretical study of near-field heat transfer between two
uniaxial anisotropic planar structures. We investigate how the distance and
relative orientation (with respect to their optical axes) between the objects
affect the heat flux. In particular, we show that by changing the angle between
the optical axes it is possible in certain cases to modulate the net heat flux
up to 90% at room temperature, and discuss possible applications of such a
strong effect
Breakdown of detailed balance for thermal radiation by synthetic fields
In recent times the possibility of non-reciprocity in heat transfer between
two bodies has been extensively studied. In particular the role of strong
magnetic fields has been investigated. A much simpler approach with
considerable flexibility would be to consider heat transfer in synthetic
electric and magnetic fields which are easily applied. We demonstrate the
breakdown of detailed balance for the heat transfer function , i.e. the spectrum of heat transfer between two objects due to the
presence of synthetic electric and magnetic fields. The spectral measurements
carry lot more physical information and were the reason for the quantum theory
of radiation. We demonstrate explicitly the synthetic field induced
non-reciprocity in the heat transfer transmission function between two graphene
flakes and for the Casimir coupling between two objects. Unlike many other
cases of heat transfer, the latter case has interesting features of the strong
coupling. Further the presence of synthetic fields affects the mean occupation
numbers of two membranes and propose this system for the experimental
verification of the breakdown of detailed balance
Enhancement of synthetic magnetic field induced nonreciprocity via bound states in continuum in dissipatively coupled systems
The nonreciprocal propagation of light typically requires use of materials
like ferrites or magneto-optical media with a strong magnetic bias or methods
based on material nonlinearities which require use of strong electromagnetic
fields. A simpler possibility to produce nonreciprocity is to use
spatio-temporal modulations to produce magnetic fields in synthetic dimensions.
In this paper we show that dissipatively coupled systems can lead to
considerable enhancement of nonreciprocity in synthetic fields. The enhancement
comes about from the existence of nearly nondecaying mode -bound state in
continuum (BIC) in dissipatively coupled systems. The dissipative coupling
occurs in a wide class of systems coupled via transmission lines, waveguides,
or nano fibers. The systems could be optical resonators or microscopic qubits.
Remarkably we find that for specific choice of the modulation amplitudes, the
transmission say in forward direction is completely extinguished whereas in the
backward direction it becomes maximum. The synthetic fields produce
transmission resonances which show significant line narrowing which owe their
origin to existence of BIC's in dissipative systems
The plasmonic eigenvalue problem
A plasmon of a bounded domain is a non-trivial
bounded harmonic function on which is
continuous at and whose exterior and interior normal
derivatives at have a constant ratio. We call this ratio a
plasmonic eigenvalue of . Plasmons arise in the description of
electromagnetic waves hitting a metallic particle . We investigate
these eigenvalues and prove that they form a sequence of numbers converging to
one. Also, we prove regularity of plasmons, derive a variational
characterization, and prove a second order perturbation formula. The problem
can be reformulated in terms of Dirichlet-Neumann operators, and as a side
result we derive a formula for the shape derivative of these operators.Comment: 22 pages; replacement 8-March-14: minor corrections; to appear in
Review in Mathematical Physic
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