383 research outputs found
A modal model for diffraction gratings
A description of an algorithm for a rather general modal grating calculation
is presented. Arbitrary profiles, depth, and permittivity are allowed. Gratings
built up from sub-gratings are allowed, as are coatings on the sidewalls of
lines, and arbitrary complex structure. Conical angles and good conductors are
supported
Symmetry for the duration of entropy-consuming intervals
We introduce the violation fraction as the cumulative fraction of
time that a mesoscopic system spends consuming entropy at a single trajectory
in phase space. We show that the fluctuations of this quantity are described in
terms of a symmetry relation reminiscent of fluctuation theorems, which involve
a function, , which can be interpreted as an entropy associated to the
fluctuations of the violation fraction.
The function , when evaluated for arbitrary stochastic realizations of
the violation fraction, is odd upon the symmetry transformations which are
relevant for the associated stochastic entropy production. This fact leads to a
detailed fluctuation theorem for the probability density function of .
We study the steady-state limit of this symmetry in the paradigmatic case of
a colloidal particle dragged by optical tweezers through an aqueous solution.
Finally, we briefly discuss on possible applications of our results for the
estimation of free-energy differences from single molecule experiments.Comment: 11 pages, 4 figures. Last revised. Version accepted for publication
in Phys. Rev.
Engineering of intelligent reflecting surfaces: Reflection locality and angular stability
Reconfigurable intelligent surfaces (RISs) are electromagnetically passive
controllable structures, deflecting the incident wave beam in directions
predefined by the control signal. A usual way to design RIS based on
metasurfaces (MSs) is based on the application of the approximation in which
the reflective properties of a uniform MS are attributed to a unit cell of the
non-uniform one. We call this approximation the reflection locality. In the
present paper, we show that this approximation may result in heavy errors. We
also find a condition under which this approximation is applicable for a wide
range of incidence and deflection angles. This condition is the angular
stability of the reflection phase of a uniform MS based on which the
non-uniform one is generated. We present an approximate analytical proof of the
equivalence of the reflection locality and angular stability. As an example, we
report theoretical and experimental results we obtained for a binary RIS whose
generic uniform analogue has the angular stability. Meanwhile, for its
counterpart without angular stability (the so-called mushroom MS) the same
model fails
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