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ABSTRACT: We experimentally show that the self-phase modulation of picosecond pump pulses, induced by both the optical Kerr effect and free-carrier refraction, has a detrimental effect on the maximum on-off Raman gain achievable in silicon on insulator nanowaveguides, causing it to saturate. A simple calculation of the Raman gain coefficient from the measured broadened output pump spectra perfectly matches the saturated behavior of the amplified Raman signal observed experimentally at different input pump powers.
Applied Physics Letters 07/2010; · 3.84 Impact Factor
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ABSTRACT: Nonlinear propagation experiments in GaAs photonic crystal waveguides (PCW) were performed, which exhibit a large enhancement of third order nonlinearities, due to light propagation in a slow mode regime, such as two-photon absorption (TPA), optical Kerr effect and refractive index changes due to free-carriers generated by TPA. A theoretical model has been established that shows a very good quantitative agreement with experimental data and demonstrates the important role that the group velocity plays. These observations give a strong insight into the use of PCWs for optical switching devices.
Optics Express 02/2009; 17(2):552-7. · 3.59 Impact Factor
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ABSTRACT: Kerr and four-wave mixing spectroscopy is shown to be a powerful technique to quantify the strong enhancement of the third-order optical nonlinear susceptibilities at the band edge of photonic crystals. Local field factors of about 5 are demonstrated for crossed Kerr effect and a narrow resonance peak observed for the conjugate reflectivity. Moreover, a reduction of the effective nonlinear susceptibility of the four-wave mixing process with increasing pump intensities is measured, which is due to different Kerr-induced blueshifts of the band edge for forward and backward pump beams and signal and conjugate beams. This observation definitely demonstrates the need for considering all the nonlinear processes for the optimization of nonlinear photonic crystals for a given application in optical signal processing.
Applied Physics Letters 07/2005; · 3.84 Impact Factor
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ABSTRACT: The non-infinite contrast of the spatial light modulators used to modulate the recording and readout beams in dynamic holographic interconnects induces noise. We show that this noise can be easily computed. It increases with the system capacity. If nothing is done to prevent it, then most of the holographic neural networks previously proposed in the literature are limited to uninteresting capacities. Based on the deterministic nature of this noise source, we propose various techniques to reduce it. These techniques can be easily implemented on any setup. We believe that the resulting gain in capacity considerably renews the interest for these holographic neural networks.
07/2003;
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ABSTRACT: We present a demonstration of the influence of the indirect electro-optic effect on the photorefractive performance of Ba <sub>0.77</sub> Ca <sub>0.23</sub> TiO <sub>3</sub> (BCT). The comparison of the orientation dependence of the two-beam coupling energy transfer gain with theoretical model allows us to obtain information on the electro-optic coefficients, but also an evaluation of the unknown elasto-optic, piezoelectric, and elastic stiffness coefficients of BCT. We found r<sub>13</sub><sup>T</sup>=33 pm V <sup>-1</sup> and r<sub>33</sub><sup>T</sup>=170 pm V <sup>-1</sup>. These values are in good agreement with other published values. For the interesting coefficient r<sub>42</sub><sup>T</sup>, we find a higher value r<sub>42</sub><sup>T</sup>=465 pm V <sup>-1</sup> than the one previously published. From this study we also determine that as in the case of BaTiO <sub>3</sub>, the optimal orientation is given by a 45°-cut BCT. © 2002 American Institute of Physics.
Journal of Applied Physics 12/2002; · 2.17 Impact Factor
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ABSTRACT: In this paper we describe the realization and the operation of a high capacity optoelectronic neural network implementing a classification of vectors through a Kohonen topological map. The setup uses volume holographic interconnects inside a photorefractive crystal to implement the neurons. We show that the system work and is able to classify several tens of vectors.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
05/2000;
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Alexandre Baron,
Aleksandr Ryasnyanskiy,
Nicolas Dubreuil,
Philippe Delaye,
Quynh Vy Tran,
Sylvain Combrié,
Alfredo De Rossi,
Robert Frey, Gerald Roosen,
N G R Broderick,
P Millar,
D J Richardson,
J S Aitchson,
R De La,
E Ralph,
R P Kenan,
C M Verber,
A J Springthorpe
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ABSTRACT: Nonlinear propagation experiments in GaAs photonic crystal waveguides (PCW) were performed, which exhibit a large enhancement of third order nonlinearities, due to light propagation in a slow mode regime, such as two-photon absorption (TPA), optical Kerr effect and refractive index changes due to free-carriers generated by TPA. A theoretical model has been established that shows a very good quantitative agreement with experimental data and demonstrates the important role that the group velocity plays. These observations give a strong insight into the use of PCWs for optical switching devices.
Optics Express 01/2000; 25(53):740-742. · 3.59 Impact Factor
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ABSTRACT: We demonstrate that a parametrically pumped picosecond laser has enough coherence and energy to write transient phase gratings at nonresonant interaction, thus allowing a study of time-resolved carrier transport in CdTe crystals to be made. Autocorrelation trace of light diffraction efficiency on transient grating allowed us to measure a coherence length of the parametric generator. Carrier diffusion, recombination, and drift in light-created internal space-charge (SC) electric fields have been studied in vanadium or germanium doped semi-insulating CdTe crystals by nonresonant four-wave mixing technique at 940 nm wavelength. It was found that modification of the deep level charge state in CdTe:V by As codoping has changed the sign of majority carriers, responsible for the creation of SC field. Dynamics of free carrier grating decay in CdTe:Ge revealed an electron-governed very fast initial grating decay which develops with time into the double-exponential hole-governed grating decay. Time-resolved transient grating technique described in this article provides a powerful tool for investigation of the role of deep traps in photorefractive semiconductors and optimization of their photoelectric properties in a required temporal and spectral range. © 1998 American Institute of Physics.
Review of Scientific Instruments 10/1998; 69(11):3776-3779. · 1.37 Impact Factor
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Proc SPIE 07/1994; 2097:474-482.
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Ferroelectrics. 09/1987; 75(1):281-294.
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ABSTRACT: A very simple model has been developed to describe the diffractive properties of a crossed grating structure of the refractive index formed by a thin transmission grating recorded in a Bragg reflector. When the Bragg con-dition of the transmission grating coincides with the band edge of the reflection grating seen as a one-dimensional photonic crystal, the diffraction efficiency and wavelength selectivity of the transmission grating are highly enhanced and a Bragg diffraction regime can be obtained, even in very thin samples. The model can be used to design micrometric very efficient new diffracting devices for optical signal processing.
01/1950; 230.
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Harold MH Chong,
Richard M. De La Rue,
Liam O'Faolain,
Thomas F Krauss,
Nadia Belabas,
Arial Levenson,
Fabrice Raineri,
Rama Raj,
Isabelle Sagnes,
Dominique Coquillat,
Magali Astic,
Philippe Delaye,
Philippe Lalanne,
Robert Frey, Gerald Roosen
