477 research outputs found
Phase retrieval of reflection and transmission coefficients from Kramers-Kronig relations
Analytic and passivity properties of reflection and transmission coefficients
of thin-film multilayered stacks are investigated. Using a rigorous formalism
based on the inverse Helmholtz operator, properties associated to causality
principle and passivity are established when both temporal frequency and
spatial wavevector are continued in the complex plane. This result extends the
range of situations where the Kramers-Kronig relations can be used to deduce
the phase from the intensity. In particular, it is rigorously shown that
Kramers-Kronig relations for reflection and transmission coefficients remain
valid at a fixed angle of incidence. Possibilities to exploit the new
relationships are discussed.Comment: submitted for publicatio
Spectral efficiency of engineered thermal cloaks in the frequency regime
We analyse basic thermal cloaks designed via different geometric transforms
applied to thermal cloaking. We evaluate quantitatively the efficiency of these
heterogeneous anisotropic thermal cloaks through the calculation of the
standard deviation of the isotherms. The study addresses the frequency regime
and we point out the cloak's spectral efficiencies. We find that all these
cloaks have comparable efficiency irrespective of whether or not they have
singular conductivity at their inner boundary. However, approximate cloaking
with multi-layered cloak critically depends upon the homogenization algorithm
and a large number of thin layers (at least fifty) is required to reduce
substantially the standard deviation of the isotherms.Comment: 13 pages, 7 figures. The results from this article will be presented
on a poster at the Metamaterials 2014 Copenhague conferenc
Réponse au comment de Hal intitulé " Commentaire de " Transformation thermodynamics : cloaking and concentrating heat flux ", hal-00741585, version 1 - 14 octobre 2012 "
Reply to comment on " Transformation thermodynamics : cloaking and concentrating heat flux ", hal-00741585, version 1 - 14 octobre 2012
Optical scatter of quantum noise filter cavity optics
Optical cavities to filter squeezed light for quantum noise reduction require
optics with very low scattering losses. We report on measured light scattering
from two super-polished fused silica optics before and after applying
highly-reflective ion-beam sputtered dielectric coatings. We used an imaging
scatterometer that illuminates the sample with a linearly polarized 1064 nm
wavelength laser at a fixed angle of incidence and records images of back
scatter for azimuthal angles in the plane of the laser beam. We extract from
these images the bidirectional reflectance distribution function (BRDF) of the
optics with and without coating and estimate their integrated scatter. We find
that application of these coatings led to a more than 50% increase of the
integrated wide-angle scatter, to 5.00+/-0.30 and 3.38+/-0.20 ppm for the two
coated samples. In addition, the BRDF function of the coated optics takes on a
pattern of maxima versus azimuthal angle. We compare with a scattering model to
show that this is qualitatively consistent with roughness scattering from the
coating layer interfaces. These results are part of a broader study to
understand and minimize optical loss in quantum noise filter cavities for
interferometric gravitational-wave detectors. The scattering measured for these
samples is acceptable for the 16 m long filter cavities envisioned for the
Laser Interferometer Gravitational-wave Observatory (LIGO), though reducing the
loss further would improve LIGO's quantum-noise limited performance.Comment: 10 pages, 3 figure
Spatial depolarization of light from the bulks: electromagnetic prediction
International audienceThe spatial depolarization of light emitted by heterogeneous bulks is predicted with exact electromagnetic theories. The sample microstructure and geometry is connected with partial polarization
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