114 research outputs found
Differential description and irreversibility of depolarizing light-matter interactions
The widely-used Jones and Mueller differential polarization calculi allow
non-depolarizing deterministic polarization interactions, known to be elements
of the Lorentz group, to be described in an efficient way. In this
Letter, a stochastic differential Jones formalism is shown to provide a clear
physical insight on light depolarization, which arises from the interaction of
polarized light with a random medium showing fluctuating anisotropic
properties. Based on this formalism, several "intrinsic" depolarization metrics
naturally arise to efficiently characterize light depolarization in a medium,
and an irreversibility property of depolarizing transformations is finally
established
Adaptive polarimetric image representation for contrast optimization of a polarized beacon through fog
We present a contrast-maximizing optimal linear representation of
polarimetric images obtained from a snapshot polarimetric camera for enhanced
vision of a polarized light source in obscured weather conditions (fog, haze,
cloud) over long distances (above 1 km). We quantitatively compare the gain in
contrast obtained by different linear representations of the experimental
polarimetric images taken during rapidly varying foggy conditions. It is shown
that the adaptive image representation that depends on the correlation in
background noise fluctuations in the two polarimetric images provides an
optimal contrast enhancement over all weather conditions as opposed to a simple
difference image which underperforms during low visibility conditions. Finally,
we derive the analytic expression of the gain in contrast obtained with this
optimal representation and show that the experimental results are in agreement
with the assumed correlated Gaussian noise model
Depolarization remote sensing by orthogonality breaking
A new concept devoted to sensing the depolarization strength of materials
from a single measurement is proposed and successfully validated on a variety
of samples. It relies on the measurement of the orthogonality breaking between
two orthogonal states of polarization after interaction with the material to be
characterized. The two fields orthogonality being preserved after propagation
in birefringent media, this concept is shown to be perfectly suited to
depolarization remote sensing through fibers, opening the way to real time
depolarization endoscopy.Comment: 5 pages, 4 figure
Theoretical optimal modulation frequencies for scattering parameter estimation and ballistic photon filtering in diffusive media
The efficiency of using intensity modulated light for estimation of
scattering properties of a turbid medium and for ballistic photon
discrimination is theoretically quantified in this article. Using the diffusion
model for modulated photon transport and considering a noisy quadrature
demodulation scheme, the minimum-variance bounds on estimation of parameters of
interest are analytically derived and analyzed. The existence of a
variance-minimizing optimal modulation frequency is shown and its evolution
with the properties of the intervening medium is derived and studied.
Furthermore, a metric is defined to quantify the efficiency of ballistic photon
filtering which may be sought when imaging through turbid media. The analytical
derivation of this metric shows that the minimum modulation frequency required
to attain significant ballistic discrimination depends only on the reduced
scattering coefficient of the medium in a linear fashion for a highly
scattering medium
General Cram\'er-Rao bound for parameter estimation using Gaussian multimode quantum resources
Multimode Gaussian quantum light, including multimode squeezed and/or
multipartite quadrature entangled light, is a very general and powerful quantum
resource with promising applications to quantum information processing and
metrology involving continuous variables. In this paper, we determine the
ultimate sensitivity in the estimation of any parameter when the information
about this parameter is encoded in such Gaussian light, irrespective of the
exact information extraction protocol used in the estimation. We then show
that, for a given set of available quantum resources, the most economical way
to maximize the sensitivity is to put the most squeezed state available in a
well-defined light mode. This implies that it is not possible to take advantage
of the existence of squeezed fluctuations in other modes, nor of quantum
correlations and entanglement between different modes. We show that an
appropriate homodyne detection scheme allows us to reach this Cramr-Rao bound.
We apply finally these considerations to the problem of optimal phase
estimation using interferometric techniques
Contrast enhancement in polarimetric imaging with correlated noise fluctuations
International audienceWe compare the measurement precision of a polarimetric camera to that of a simple intensity camera when imaging a partially polarized light-mark embedded in an intense and partially polarized background. We show that the gain in measurement precision while using a polarimetric camera is maximized when the noise fluctuations on the two polarimetric channels are significantly correlated. Further, we implement a snapshot polarimetric camera for long distance imaging of a highly polarized light source through fog and compare the contrast obtained using various representations of the polarimetric images. We show that the representation that provides the best contrast depends on the visibility conditions and matches well with theoretical predictions
Depolarization Sensing by Orthogonality Breaking: a microwave-photonics approach for snapshot polarimetric imaging
International audienceWe report a new depolarization sensing modality (DSOB), based on the concept of polarization orthogonality breaking, enabling direct measurement of a polarimetric contrast from a single measurement. The principle of this technique is described, as well as its benefits (compatibility with remote sensing through fibers, spectral agility…). Experimental validation of this technique on a fibred setup is extensively described and confirms its appropriateness for remote sensing through optical fibers. We eventually present the first DSOB images obtained in the visible range on a confocal microscope setup. The acquisition times reported are encouraging for future implementation in real-time
Optimal estimation in polarimetric imaging in the presence of correlated noise fluctuations
International audienceWe quantitatively analyze how a polarization-sensitive imager can overcome the precision of a standard intensity camera when estimating a parameter on a polarized source over an intense background. We show that the gain is maximized when the two polarimetric channels are perturbed with significantly correlated noise fluctuations. An optimal estimator is derived and compared to standard intensity and polarimetric estimators
Generalized Jones matrix method for homogeneous biaxial samples
International audienceThe generalized Jones matrix (GJM) is a recently introduced tool to describe linear transformations of three-dimensional light fields. Based on this framework, a specific method for obtaining the GJM of uniaxial anisotropic media was recently presented. However, the GJM of biaxial media had not been tackled so far, as the previous method made use of a simplified rotation matrix that lacks a degree of freedom in the three-dimensional rotation, thus being not suitable for calculating the GJM of biaxial media. In this work we propose a general method to derive the GJM of arbitrarily-oriented homogeneous biaxial media. It is based on the differential generalized Jones matrix (dGJM), which is the three-dimensional counterpart of the conventional differential Jones matrix. We show that the dGJM provides a simple and elegant way to describe uniaxial and biaxial media, with the capacity to model multiple simultaneous optical effects. The practical usefulness of this method is illustrated by the GJM modeling of the polarimetric properties of a negative uniaxial KDP crystal and a biaxial KTP crystal for any three-dimensional sample orientation. The results show that this method constitutes an advantageous and straightforward way to model biaxial media, which show a growing relevance for many interesting applications
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