Research Interests:
Research Interests:
... This restoration has been experimentally obtained by placing a mirror after the crystal to obtain a back-propagating wave that ... [21]GJ Whitman and DB Kopans, Mammography, in Advances ... [26] MI Kolobov and LA Lugiato, ... more
... This restoration has been experimentally obtained by placing a mirror after the crystal to obtain a back-propagating wave that ... [21]GJ Whitman and DB Kopans, Mammography, in Advances ... [26] MI Kolobov and LA Lugiato, Noiseless amplification of optical images, Phys. Rev. ...
Research Interests:
Spontaneous down conversion (SPDC) occurs in a nonlinear crystal when a pump photon splits in a pair of signal and idler photons. This paper demonstrates detection of single photons in low light level images with an electron multiplying... more
Spontaneous down conversion (SPDC) occurs in a nonlinear crystal when a pump photon splits in a pair of signal and idler photons. This paper demonstrates detection of single photons in low light level images with an electron multiplying CCD camera (EMCCD). The opposite spatial fluctuations of SPDC radiation are correlated in the quantum regime. Here, correlations between pixels are presented for collinear phase matching. The far field image of the parametric fluorescence is formed in the focal plane of a lens on a back-illuminated EMCCD. A thresholding procedure is applied on each image, in order to decide whether there is one or zero photo-electron on each pixel. We have experimentally demonstrated that spatial SPDC fluctuations between opposite pixels are quantum correlated in the far field.
Research Interests:
Ultrafast turbidity compensation in the optical therapeutic window by three-wave mixing phase conjugation
We present an experiment of temporal ghost imaging based on the spatial properties of twin photons. The retrieval of a binary time signal of 8 bits is performed with an error rate of 0.70%.
Research Interests:
At first sight, the use of an everywhere positive Wigner function as a probability density to perform stochastic simulations in quantum optics seems equivalent to the introduction of local hidden variables, thus preventing any violation... more
At first sight, the use of an everywhere positive Wigner function as a probability density to perform stochastic simulations in quantum optics seems equivalent to the introduction of local hidden variables, thus preventing any violation of Bell inequalities. However, because of the difference between symmetrically and normally ordered operators, some trajectories in stochastic simulations can imply negative intensities, despite a positive mean. Hence, Bell inequalities do not apply. Here, we retrieve for a weakly squeezed Gaussian state the maximum violation on polarization states allowed by quantum mechanics, for the Clauser-Horn-Shimony-Holt (CHSH), as well as for the Clauser-Horn Bell inequalities. For the case of the Clauser-Horn Bell inequality, the influence of the quantum efficiency of the detectors is studied, and for both inequalities, the influence of the degree of squeezing is assessed, as well as the uncertainty range versus the number of trajectories used in the simulat...
Research Interests:
Research Interests:
Research Interests:
The dynamical Casimir effect is the generation of pairs of real particles or photons from the vacuum as a result of a non-adiabatic change of a system parameter or boundary condition. As opposed to standard parametric amplification where... more
The dynamical Casimir effect is the generation of pairs of real particles or photons from the vacuum as a result of a non-adiabatic change of a system parameter or boundary condition. As opposed to standard parametric amplification where the modulation occurs both in space and in time, this fundamental process requires a pure modulation in time, which makes its detection particularly challenging at optical frequencies. In this paper we experimentally demonstrate a realization of the analogue dynamical Casimir effect in the near-infrared optical regime in a dispersion-oscillating photonic crystal fibre. The experiments are based on the equivalence of the spatial modulation of the fibre core diameter to a pure temporal modulation when this is considered in the co-moving frame of the travelling pump pulse. We provide evidence of optical dynamical Casimir effect by measuring quantum correlations between the spectrally resolved photon pairs and prove their non-classical nature with photo...
Research Interests:
Research Interests:
Image parametric amplification and its applications are summarized. The link between resolution and phase matching is presented. Then applications to ultrafast imaging and imaging through diffusing media are given. Last, degenerate... more
Image parametric amplification and its applications are summarized. The link between resolution and phase matching is presented. Then applications to ultrafast imaging and imaging through diffusing media are given. Last, degenerate schemes are proved to permit polychromatic amplification as well as phase-sensitive amplification.
Research Interests:
Research Interests:
Research Interests:
Open any physics textbook and you'll soon come across what English-speaking physicists refer to as "Snell's law". The principle of refraction – familiar to anyone who has dabbled in optics – is named after the Dutch... more
Open any physics textbook and you'll soon come across what English-speaking physicists refer to as "Snell's law". The principle of refraction – familiar to anyone who has dabbled in optics – is named after the Dutch scientist Willebrord Snell (1591–1626), who first stated the law in a manuscript in 1621. In French, however, the same law is often called "la loi de Descartes" because it was Rene Descartes (1596–1650) who first put the law into widespread circulation in his Discourse on Method, published in 1637.
Research Interests:
ABSTRACT Summary form only given. Ultrafast all-optical wavelength conversion between widely-spaced channels is a significant function in optical telecommunications. Several techniques have been demonstrated for wavelength conversion from... more
ABSTRACT Summary form only given. Ultrafast all-optical wavelength conversion between widely-spaced channels is a significant function in optical telecommunications. Several techniques have been demonstrated for wavelength conversion from 1.3 μm to 1.5 μm, using nonlinear optical loop mirrors, semiconductor optical amplifiers, Raman resonant four-wave mixing process in birefringent optical fibers, or difference frequency generation in quadratic periodically poled waveguides. However, the maximum conversion efficiency was about -9 dB for all techniques, essentially limited by phase-matching constraints. We address a new technique based on Raman-assisted three-wave mixing (RATWM) process in optical fibers. This simple wide-range wavelength conversion technique does not require the fulfilment of stringent phase-matching, which permits flexible operating conditions. We present coupled mode calculations and numerical simulations of the nonlinear Schrodinger equation (NLSE) showing, in a simplified architecture involving purposely designed nonlinear dispersion-shifted fibers (DSFs), efficient wavelength conversion of a 1.31 μm input signal to an output signal in the 1.5 μm spectral region
Research Interests:
Research Interests:
ABSTRACT In this paper we present results of real-time imaging through biological tissues by means of nonlinear three-wave mixing phase conjugation process. Biological tissues with thicknesses up to 5 mm are used and the imaging process... more
ABSTRACT In this paper we present results of real-time imaging through biological tissues by means of nonlinear three-wave mixing phase conjugation process. Biological tissues with thicknesses up to 5 mm are used and the imaging process is performed at a near infrared wavelength included in the therapeutic window. Furthermore we show that real-time compensation of turbidity of biological tissues allowed with this method can be applied to scattering media in motion, with a significant improvement of the signal to noise ratio and resolution of the restored images.
Research Interests:
We report semi-classical numeric simulations of the quantum spatial fluctuations in parametric amplification of images limited by the shot noise. Noiseless amplification of images is demonstrated by the use of a degenerate type 2 phase... more
We report semi-classical numeric simulations of the quantum spatial fluctuations in parametric amplification of images limited by the shot noise. Noiseless amplification of images is demonstrated by the use of a degenerate type 2 phase sensitive amplifier.
Research Interests:
The linewidth measurement on wafers depends on the small local irregularities in the region being tested. Such defects must be first of all detected and then canceled in order to give an estimation of the average linewidth. Image... more
The linewidth measurement on wafers depends on the small local irregularities in the region being tested. Such defects must be first of all detected and then canceled in order to give an estimation of the average linewidth. Image processing based on the Karhunen-Loeve transform of multiple acquisitions in different experimental conditions is proposed. Using statistical information compression, irregularities are easily detected and efficient noise filtering is performed.
Research Interests:
Research Interests:
Abstract Summary form only given. A lot of theoretical and experimental work has been done this last decade an single spatial soliton propagation and twin-soliton interactions in planar Kerr waveguides, as it is well known that Kerr... more
Abstract Summary form only given. A lot of theoretical and experimental work has been done this last decade an single spatial soliton propagation and twin-soliton interactions in planar Kerr waveguides, as it is well known that Kerr solitons can only be stable in a (1+ 1) D geometry. The (1+ 1) D nonlinear Schrodinger equation that governs soliton propagation also governs modulational instability, a parametric wave mixing process which amplifies, spatially speaking, weak transverse perturbations or periodic modulations of an intense ...
Research Interests:
ABSTRACT This study shows that the spatial jitter of the soliton arrays depends on the shot-to-shot degree of correlation of the spatial noise. This correlation degree is strongly dependent on the spatio-temporal coherence of the injected... more
ABSTRACT This study shows that the spatial jitter of the soliton arrays depends on the shot-to-shot degree of correlation of the spatial noise. This correlation degree is strongly dependent on the spatio-temporal coherence of the injected beam.
Research Interests: Physics, Optics, Optical Waveguides, Solitons, Frequency, and 4 moreShot Noise, Coherence, Jitter, and Soliton
Research Interests:
Research Interests:
Parametric wave-mixing in dielectric media have been intensively investigated for both its fundamental and applied interests [1].
Research Interests:
Research Interests:
We present experiments and related numerical simulations on spatial induced modulational instability, which is used to study periodic arrays of bright soliton-like beams in a planar CS 2 waveguide. In the picosecond regime the finite... more
We present experiments and related numerical simulations on spatial induced modulational instability, which is used to study periodic arrays of bright soliton-like beams in a planar CS 2 waveguide. In the picosecond regime the finite molecular relaxation time of the nonlinear refraction contributes to inhibiting the periodic recurrence, thus stabilizing the propagation of the soliton-like array.
Research Interests:
Research Interests:
Research Interests:
It is demonstrated that the least square method is unable to separate a linear drift and a low-frequency noise. Moreover, the use of a single variance cannot distinguish a linear frequency drift from a f/sup 2/ frequency noise if it is... more
It is demonstrated that the least square method is unable to separate a linear drift and a low-frequency noise. Moreover, the use of a single variance cannot distinguish a linear frequency drift from a f/sup 2/ frequency noise if it is calculated in the frequency domain, or a linear frequency drift from a f/sup 3/ frequency noise if it is calculated in the time domain. Since f/sup 3/ frequency noise may be encountered in pulsar timing data, this latter solution cannot be used. Hence, the multivariance method using variances calculated in both time and frequency domains seems to be the best solution in this case. Moreover, the great separability of a multivariance system using two types of variances increases the interest of this method.<<ETX>>
Research Interests:
Assuming a power law noise model of the power spectral density, the time stability of oscillators may be characterized by several noise levels. In the case of levels of the same order of magnitude, the multivariance method yields a... more
Assuming a power law noise model of the power spectral density, the time stability of oscillators may be characterized by several noise levels. In the case of levels of the same order of magnitude, the multivariance method yields a measurement of the levels and an assessment of the measurement precision. On the other hand, in the case of a noise
Research Interests:
Since the noise altering the output signal of oscillators may be modeled as power laws in the spectral density of frequency deviation, the oscillator noise analysis is the measurement of the level of each power law noise. The principle of... more
Since the noise altering the output signal of oscillators may be modeled as power laws in the spectral density of frequency deviation, the oscillator noise analysis is the measurement of the level of each power law noise. The principle of this new multivariance method consists in obtaining the noise type contributions with different variances and different integration time values. The
Research Interests:
Research Interests:
In some applications of time metrology, the measurement cannot be regularly spaced in time. This problem occurs for instance in the case of time transfer using GPS satellites in common view, since it is necessary to wait to see the same... more
In some applications of time metrology, the measurement cannot be regularly spaced in time. This problem occurs for instance in the case of time transfer using GPS satellites in common view, since it is necessary to wait to see the same satellite from the two clocks being compared. This problem may also be observed in millisecond pulsar timing measurements since pulsars cannot be observed at regularly spaced dates. However, it is important to measure the time stability in these cases. We developed several methods of spectral analysis of irregularly spaced data based upon the multi-variance method. The first class of methods involves different types of interpolation of the missing data, as described in Vernotte et al. (1993). The second class is an adaptation, in the multi-variance framework, of the lowest mode estimator introduced by Deeter and Boynton (1982). The details of these methods are described. In order to compare their efficiency, we applied all of these methods over different types of simulated signals discussed the results.
Research Interests:
Research Interests:
The multi-variance analysis yields a better sensitivity for the measurement of the frequency noise altering the oscillators as well as an estimation of the measurement uncertainties. This method has been improved in order to measure... more
The multi-variance analysis yields a better sensitivity for the measurement of the frequency noise altering the oscillators as well as an estimation of the measurement uncertainties. This method has been improved in order to measure simultaneously drift and noise coefficients and non-equally spaced timing sequences. We defined a new standard of time stability measurement which is used for classical clocks as well as millisecond pulsars.<<ETX>>
Research Interests:
A simple model describing the field reflected on a trapezoidal shape highly reflecting object is proposed. This model is based on the assumption of non interference between the bottom and the top of the line under test. Some results of... more
A simple model describing the field reflected on a trapezoidal shape highly reflecting object is proposed. This model is based on the assumption of non interference between the bottom and the top of the line under test. Some results of simulation are presented and discussed.
Research Interests:
A tridimensional pseudo-spectral time domain (3D-PSTD) algorithm, that solves the full-wave Maxwell's equations by using Fourier transforms to calculate the spatial derivatives, has been applied to determine the time characteristics... more
A tridimensional pseudo-spectral time domain (3D-PSTD) algorithm, that solves the full-wave Maxwell's equations by using Fourier transforms to calculate the spatial derivatives, has been applied to determine the time characteristics of the propagation of electromagnetic waves in inhomogeneous media. Since the 3D simulation gives access to the full-vector components of the electromagnetic fields, it allowed us to analyse the polarization state of the scattered light with respect to the characteristics of the scattering medium and the polarization state of the incident light. We show that, while the incident light is strongly depolarized on the whole, the light that reaches the output face of the scattering medium is much less depolarized. This fact is consistent with our recently reported experimental results, where a rotation of the polarization does not preclude the restoration of an image by phase conjugation.
Research Interests:
ABSTRACT We demonstrate EPR entanglement by detecting with an electron-multiplying CCD (EMCCD) camera purely spatial 2-D quantum correlations in the near and far-field of spontaneous parametric down conversion generated in a type II BBO... more
ABSTRACT We demonstrate EPR entanglement by detecting with an electron-multiplying CCD (EMCCD) camera purely spatial 2-D quantum correlations in the near and far-field of spontaneous parametric down conversion generated in a type II BBO crystal.
Research Interests:
We describe a new method to measure numerically the in-plane displacement of a speckle image. Our application is the tensile test of thin films. We want to calculate the strain of the specimen for the tensile direction y and for the... more
We describe a new method to measure numerically the in-plane displacement of a speckle image. Our application is the tensile test of thin films. We want to calculate the strain of the specimen for the tensile direction y and for the transverse direction x. We need therefore to measure the in-plane displacements field of the surface of the specimen. This application has governed the choice of the method: the Spectral Phase Algorithm. This method has been compared to the technique of Intercorrelation. It is faster and more accurate in the case of small displacements.
Research Interests:
Abstract Summary form only given. In optical WDM communication systems, the 35 nm gain bandwidth available with conventional EDFAs sets a limit to the increase of transmission rates. It is important to develop new optical amplifiers in... more
Abstract Summary form only given. In optical WDM communication systems, the 35 nm gain bandwidth available with conventional EDFAs sets a limit to the increase of transmission rates. It is important to develop new optical amplifiers in several spectral ranges between 1.3 μm and 1.6 μm, with broad bandwidths and flat spectral gain profiles, another restrictive factor in long-haul systems involving repeated steps of amplification. Multi-pumped fiber Raman amplifiers and dual-band doped-host EDFAs are some of the presently developed ...
Research Interests:
Research Interests:
ABSTRACT In this paper we present a three dimensional numerical model, based on a Pseudo-Spectral Time Domain algo-rithm (PSTD), that simulates the propagation of light carrying an image through a scattering medium and the back... more
ABSTRACT In this paper we present a three dimensional numerical model, based on a Pseudo-Spectral Time Domain algo-rithm (PSTD), that simulates the propagation of light carrying an image through a scattering medium and the back propagation of the scattered light which is reflected back by a phase conjugate mirror, modelled thanks to the nonlinear optical process of three-wave-mixing. We show how the phase conjugate wave retraces the scattering path and retrieves the spatial information of the input image with a signal to noise ratio that depends on the lateral dimensions of the phase conjugate mirror and of the number of realizations cumulated. Moreover, we show that the image restoration is not precluded by the polarization change between the phase conjugate wave and the scattered light exiting the complex medium.
Research Interests:
ABSTRACT
Research Interests:
Abstract: We ,study experimentally the detrimental impact of the longitudinal variations of the chromatic dispersion on the,gain of a broadband,fiber optical parametric amplifier. Thanks to the optimization of the pump wavelength, a... more
Abstract: We ,study experimentally the detrimental impact of the longitudinal variations of the chromatic dispersion on the,gain of a broadband,fiber optical parametric amplifier. Thanks to the optimization of the pump wavelength, a 3dB-gain bandwidth of 25nm is demonstrated using only 740mW pump,power. ©2003 Optical Society of America OCIS codes:060.4370, 060.2320
Research Interests:
We have theoretically investigated a new fibre optical parametric amplifier (OPA) architecture that provides a nearly flat gain over a 100 nm bandwidth without any gain-equalization filter. It consists in a multi-section in-line... more
We have theoretically investigated a new fibre optical parametric amplifier (OPA) architecture that provides a nearly flat gain over a 100 nm bandwidth without any gain-equalization filter. It consists in a multi-section in-line dispersion-tailored NLF arrangement and a single low-power pump which meets the current telecommunications requirements. Recent experiments haw shown that this kind of OPA's would be potentially useful for telecommunications applications and the results presented here predict interesting enhanced performances.
Research Interests:
Electrical measurements of the noise figure of a fiber optical parametric amplifier are presented and compared with optical measurements. The transfer of pump noise by four-wave mixing was clearly demonstrated.