The Experts below are selected from a list of 3141 Experts worldwide ranked by ideXlab platform

Gérald Roosen - One of the best experts on this subject based on the ideXlab platform.

  • Single-mode output power enhancement of an extended cavity broad-area laser diode by an intracavity Photorefractive Crystal
    Applied Physics B - Laser and Optics, 2007
    Co-Authors: Vincent Reboud, Nicolas Dubreuil, Gilles Pauliat, Gérald Roosen, Pierre Fournet, Daniel Rytz
    Abstract:

    Brightness improvement of high-power semiconductor lasers can be achieved by placing a broad-area laser diode, used as a pure optical amplifier, in an extended cavity. We report the modal behavior of an extended cavity which contains a Photorefractive Crystal. The dynamic holographic medium that plays the role of a spatial and spectral filter acts on the transverse and axial structure of the extended cavity modes and improves the single-mode operating range of the laser. An enhancement of the brightness in single-mode operation by a factor of seven has been experimentally observed thanks to the intracavity Photorefractive Crystal.

  • Self-induced transverse mode selection in a Photorefractive extended cavity laser diode
    Optics Express, 2006
    Co-Authors: Vincent Reboud, Nicolas Dubreuil, Gilles Pauliat, Gérald Roosen, Pierre Fournet, Daniel Rytz
    Abstract:

    Previous works on Photorefractive self-organizing laser cavities were about lasers that oscillate, prior the self-organization process occurs, on a set of axial modes sharing the same transverse structure. In a welldesigned broad-area laser diode extended cavity, we theoretically and experimentally demonstrate that the insertion of a Photorefractive Crystal can also affect the transverse modal structure to force the laser, initially oscillating on several transverse modes, to oscillate on a single transverse and axial mode. This spatial self-organization process leads to an enhancement of the single mode operating range of the laser.

  • Passive introduction of carrier fringes in real time Photorefractive interferometers for single interferogram analysis
    Journal of the European Optical Society : Rapid publications, 2006
    Co-Authors: Gilles Pauliat, Gérald Roosen, Marc P. Georges, Giancarlo Pedrini
    Abstract:

    We propose a new technique to introduce carrier fringes in an holographic interferometric set-up for deformation or vibration analyses. This technique makes use of the anisotropic diffraction processes of Photorefractive Crystals. The main advantage of the proposed technique is that it just involves static components, no moving parts or active components are required. This technique is demonstrated in a real-time interferometric set-up operating at the wavelength of 1.06 µm and with a GaAs Photorefractive Crystal as the holographic medium.

  • Diffraction limited polarized emission from a multimode Yb fiber amplifier after nonlinear beam converter
    Optics Letters, 2004
    Co-Authors: Laurent Lombard, Eric Lallier, Gilles Pauliat, Arnaud Brignon, Gaëlle Lucas-leclin, Jean-pierre Huignard, Patrick Georges, Gérald Roosen
    Abstract:

    The multimode and depolarized output beam of a highly multimode diode-pumped Yb-doped fiber amplifier is converted to a diffraction-limited, linearly polarized beam by a self-referencing two-wave-mixing process in an infrared-sensitive Photorefractive Crystal (Rh:BaTiO3 ). As much as 11.6 W of single-mode output is achieved with a 78% multimode-to-single-mode Photorefractive conversion efficiency

  • Photorefractive detection of tagged photons in ultrasound modulated optical tomography of thick biological tissues
    Optics Express, 2004
    Co-Authors: François Ramaz, B.c. Forget, Michael Atlan, Albert-claude Boccara, Michel Gross, Philippe Delaye, Gérald Roosen
    Abstract:

    We present a new and simple method to obtain ultrasound modulated optical tomography images in thick biological tissues with the use of a Photorefractive Crystal. The technique offers the advantage of spatially adapting the output speckle wavefront by analysing the signal diffracted by the interference pattern between this output field and a reference beam, recorded inside the Photorefractive Crystal. Averaging out due to random phases of the speckle grains vanishes, and we can use a fast single photodetector to measure the ultrasound modulated optical contrast. This technique offers a promising way to make direct measurements within the decorrelation time scale of living tissues

Marc Sciamanna - One of the best experts on this subject based on the ideXlab platform.

  • Wideband chaos from a laser diode with phase-conjugate feedback
    Optics Letters, 2019
    Co-Authors: Guillaume Bouchez, Delphine Wolfersberger, Brice Macias, Marc Sciamanna
    Abstract:

    We analyze experimentally and theoretically the chaotic dynamics generated by a laser diode subjected to phase-conjugate feedback. Phase-conjugation is obtained from four-wave mixing in a BaT i0 3 Photorefractive Crystal. We demonstrate that the chaos bandwidth first increases linearly with the feedback ratio but then saturates to relatively high values. A chaos bandwidth up to about 18 GHz is achieved, which is more than five times larger than the free-running laser diode relaxation oscillation frequency. Numerical simulations confirm our experimental observations and unveil that the finite depth penetration into the Crystal is responsible for the observed saturation.

  • Ultraslow Light Pulse in a SPS Photorefractive Crystal at Room Temperature
    2018
    Co-Authors: Nacera Bouldja, Delphine Wolfersberger, Marc Sciamanna
    Abstract:

    We experimentally demonstrate that light can be decelerated in SPS Photorefractive Crystal. Indeed, by using a two-wave mixing process in this material, it is possible to slow-down a light pulse and simultaneously to improve the delay-bandwidth product.

  • Spatio-temporal dynamics of nonlinear Airy beam interactions
    2016
    Co-Authors: Marc Sciamanna, Noémie Wiersma, Nicolas Marsal, Delphine Wolfersberger
    Abstract:

    We review the time-dependent self-focusing of an Airy beam in a Photorefractive Crystal. The interaction between two counter-propagating Airy beams yields additional dynamics, e.g. static waveguiding, time-periodic and chaotic light trajectories.

  • Bistability of optical patterns in convective regime
    2016
    Co-Authors: Nicolas Marsal, Delphine Wolfersberger, L. Weicker, Elodie Mirisola, Marc Sciamanna
    Abstract:

    We analyze numerically and experimentally the pattern formation process in an optical system composed of a bulk Photorefractive Crystal subjected to a single optical feedback. In this configuration, the system admits an homogeneous solution for low coupling strength. Increasing the coupling strength leads to a sub-critical bifurcation which leads to a pattern state. Such a bifurcation gives access to a well-defined hysteresis. In this paper we demonstrate that the size of the bistable area can be adjusted by different system parameters such as the intensity of the input beam, the power of an external background illumination and more interestingly by the feedback mirror tilt angle.

  • Counter-propagating Airy beams in nonlinear media
    2014
    Co-Authors: Noémie Wiersma, Marc Sciamanna, Nicolas Marsal, Delphine Wolfersberger
    Abstract:

    We numerically study the interactions of two counter-propagating Airy beams in a Photorefractive Crystal. By varying the Airy beams' properties and the Photorefractive coupling strength, soliton-like interactions create new waveguide structures.

J P Monchalin - One of the best experts on this subject based on the ideXlab platform.

  • compact and fast response ultrasonic detection device based on two wave mixing in a gallium arsenide Photorefractive Crystal
    Review of Scientific Instruments, 2001
    Co-Authors: Benjamin Campagne, Alain Blouin, Lionel Pujol, J P Monchalin
    Abstract:

    An improved phase demodulator for the detection of ultrasound based on two-wave mixing (TWM) in the diffusion regime in a semi-insulating Photorefractive GaAs Crystal is presented. A new optical layout is proposed in which the total laser power is injected into the Crystal to reduce the grating buildup time. The device is then less sensitive to ambient vibrations or motion of the inspected part. Another new feature of the device is a balanced receiver based on large area InGaAs detectors. The measured rejection ratio of this balanced receiver is 50 dB. However, in this new optical configuration the signal and pump beam paths cannot be made equal which results in some sensitivity to high frequency laser phase noise. The performance of the device operated with a cw and a pulsed laser source is described. A comparison with the conventional confocal Fabry–Perot in the transmission mode is also presented. As expected, the GaAs-based TWM Photorefractive system is less sensitive than the Fabry–Perot at high frequencies but becomes more sensitive below some frequency value. For the 30 W pumping level used into the Crystal and a 1 m long Fabry–Perot with 85% reflectivity mirrors, this value was found to be about 1.5 MHz. This feature is known to be useful in the cases where low frequencies have to be detected, higher frequencies being attenuated by the material. This is the case of coarse microstructure materials or viscous or mushy materials. This Photorefractive configuration is also attractive like all Photorefractive systems for compactness and the absence of any need for active stabilization. To obtain a sensitivity equal or better than that of the confocal Fabry–Perot in the transmission mode, this new setup can be used with an InP:Fe or a CdTe:V Photorefractive Crystal under an applied field.

  • Polarization independent phase demodulation using Photorefractive two-wave mixing
    Applied Physics Letters, 1999
    Co-Authors: Philippe Delaye, J P Monchalin, Alain Blouin, Denis Drolet, Louis-anne De Montmorillon, Gérald Roosen
    Abstract:

    We describe both theoretically and experimentally a polarization independent interferometric adaptive photodetector based on Photorefractive two-wave mixing. The configuration is based on the simultaneous recording of two independent gratings in a single Photorefractive Crystal. Applied to the detection of ultrasonic signals, this interferometric photodetector operates with depolarized beams issued from multimode fibers and gives a detection limit close to the ultimate.

  • detection of ultrasonic motion of a scattering surface by two wave mixing in a Photorefractive gaas Crystal
    Applied Physics Letters, 1994
    Co-Authors: Alain Blouin, J P Monchalin
    Abstract:

    The performance of an interferometric system based on two‐wave mixing at 1.06 μm in undoped GaAs Crystal, for the remote detection of transient motion of a scattering surface, is described. In this system, the wave scattered by the surface is mixed inside the Photorefractive Crystal with a pump wave directly derived from the laser to provide the reference wave of the interferometer. The system shows several features appropriate to industrial applications, although its sensitivity is less than passive interferometric systems of the confocal Fabry–Perot type presently in use, except in the low frequency range (below 1 MHz).

  • broadband optical detection of ultrasound by two wave mixing in a Photorefractive Crystal
    Applied Physics Letters, 1991
    Co-Authors: R K Ing, J P Monchalin
    Abstract:

    A method which allows broadband (from typically 1 KHz) optical detection of ultrasound with large light gathering from a scattering surface is presented. The wave scattered by the surface is mixed inside a BaTiO3 Photorefractive Crystal with a pump wave directly derived from the laser to provide a sideband‐free reference wave. A polarization configuration which provides sensitive and linear ultrasonic displacement detection is described. This method is demonstrated by detecting laser generated ultrasound.

Gilles Pauliat - One of the best experts on this subject based on the ideXlab platform.

  • Numerical modeling of Photorefractive Crystals for self-adapting external cavity laser mirrors
    Optical and Quantum Electronics, 2009
    Co-Authors: Zhaohui Zhang, Eric C. Larkins, J.j. Lim, Nicolas Dubreuil, Gilles Pauliat, A. J. Kent, Slawomir Sujecki
    Abstract:

    The process of refractive index grating formation in a Photorefractive Crystal, used as the self-adapting spectral filter in an external cavity of a semiconductor laser, is studied using a self-consistent model. The model is based on the Finite Difference solution of the Kukhtarev equations. The results obtained are compared with the ones provided by approximate analytical models.

  • Single-mode output power enhancement of an extended cavity broad-area laser diode by an intracavity Photorefractive Crystal
    Applied Physics B - Laser and Optics, 2007
    Co-Authors: Vincent Reboud, Nicolas Dubreuil, Gilles Pauliat, Gérald Roosen, Pierre Fournet, Daniel Rytz
    Abstract:

    Brightness improvement of high-power semiconductor lasers can be achieved by placing a broad-area laser diode, used as a pure optical amplifier, in an extended cavity. We report the modal behavior of an extended cavity which contains a Photorefractive Crystal. The dynamic holographic medium that plays the role of a spatial and spectral filter acts on the transverse and axial structure of the extended cavity modes and improves the single-mode operating range of the laser. An enhancement of the brightness in single-mode operation by a factor of seven has been experimentally observed thanks to the intracavity Photorefractive Crystal.

  • Self-induced transverse mode selection in a Photorefractive extended cavity laser diode
    Optics Express, 2006
    Co-Authors: Vincent Reboud, Nicolas Dubreuil, Gilles Pauliat, Gérald Roosen, Pierre Fournet, Daniel Rytz
    Abstract:

    Previous works on Photorefractive self-organizing laser cavities were about lasers that oscillate, prior the self-organization process occurs, on a set of axial modes sharing the same transverse structure. In a welldesigned broad-area laser diode extended cavity, we theoretically and experimentally demonstrate that the insertion of a Photorefractive Crystal can also affect the transverse modal structure to force the laser, initially oscillating on several transverse modes, to oscillate on a single transverse and axial mode. This spatial self-organization process leads to an enhancement of the single mode operating range of the laser.

  • Passive introduction of carrier fringes in real time Photorefractive interferometers for single interferogram analysis
    Journal of the European Optical Society : Rapid publications, 2006
    Co-Authors: Gilles Pauliat, Gérald Roosen, Marc P. Georges, Giancarlo Pedrini
    Abstract:

    We propose a new technique to introduce carrier fringes in an holographic interferometric set-up for deformation or vibration analyses. This technique makes use of the anisotropic diffraction processes of Photorefractive Crystals. The main advantage of the proposed technique is that it just involves static components, no moving parts or active components are required. This technique is demonstrated in a real-time interferometric set-up operating at the wavelength of 1.06 µm and with a GaAs Photorefractive Crystal as the holographic medium.

  • Diffraction limited polarized emission from a multimode Yb fiber amplifier after nonlinear beam converter
    Optics Letters, 2004
    Co-Authors: Laurent Lombard, Eric Lallier, Gilles Pauliat, Arnaud Brignon, Gaëlle Lucas-leclin, Jean-pierre Huignard, Patrick Georges, Gérald Roosen
    Abstract:

    The multimode and depolarized output beam of a highly multimode diode-pumped Yb-doped fiber amplifier is converted to a diffraction-limited, linearly polarized beam by a self-referencing two-wave-mixing process in an infrared-sensitive Photorefractive Crystal (Rh:BaTiO3 ). As much as 11.6 W of single-mode output is achieved with a 78% multimode-to-single-mode Photorefractive conversion efficiency

Delphine Wolfersberger - One of the best experts on this subject based on the ideXlab platform.

  • Wideband chaos from a laser diode with phase-conjugate feedback
    Optics Letters, 2019
    Co-Authors: Guillaume Bouchez, Delphine Wolfersberger, Brice Macias, Marc Sciamanna
    Abstract:

    We analyze experimentally and theoretically the chaotic dynamics generated by a laser diode subjected to phase-conjugate feedback. Phase-conjugation is obtained from four-wave mixing in a BaT i0 3 Photorefractive Crystal. We demonstrate that the chaos bandwidth first increases linearly with the feedback ratio but then saturates to relatively high values. A chaos bandwidth up to about 18 GHz is achieved, which is more than five times larger than the free-running laser diode relaxation oscillation frequency. Numerical simulations confirm our experimental observations and unveil that the finite depth penetration into the Crystal is responsible for the observed saturation.

  • Ultraslow Light Pulse in a SPS Photorefractive Crystal at Room Temperature
    2018
    Co-Authors: Nacera Bouldja, Delphine Wolfersberger, Marc Sciamanna
    Abstract:

    We experimentally demonstrate that light can be decelerated in SPS Photorefractive Crystal. Indeed, by using a two-wave mixing process in this material, it is possible to slow-down a light pulse and simultaneously to improve the delay-bandwidth product.

  • Spatio-temporal dynamics of nonlinear Airy beam interactions
    2016
    Co-Authors: Marc Sciamanna, Noémie Wiersma, Nicolas Marsal, Delphine Wolfersberger
    Abstract:

    We review the time-dependent self-focusing of an Airy beam in a Photorefractive Crystal. The interaction between two counter-propagating Airy beams yields additional dynamics, e.g. static waveguiding, time-periodic and chaotic light trajectories.

  • Bistability of optical patterns in convective regime
    2016
    Co-Authors: Nicolas Marsal, Delphine Wolfersberger, L. Weicker, Elodie Mirisola, Marc Sciamanna
    Abstract:

    We analyze numerically and experimentally the pattern formation process in an optical system composed of a bulk Photorefractive Crystal subjected to a single optical feedback. In this configuration, the system admits an homogeneous solution for low coupling strength. Increasing the coupling strength leads to a sub-critical bifurcation which leads to a pattern state. Such a bifurcation gives access to a well-defined hysteresis. In this paper we demonstrate that the size of the bistable area can be adjusted by different system parameters such as the intensity of the input beam, the power of an external background illumination and more interestingly by the feedback mirror tilt angle.

  • Counter-propagating Airy beams in nonlinear media
    2014
    Co-Authors: Noémie Wiersma, Marc Sciamanna, Nicolas Marsal, Delphine Wolfersberger
    Abstract:

    We numerically study the interactions of two counter-propagating Airy beams in a Photorefractive Crystal. By varying the Airy beams' properties and the Photorefractive coupling strength, soliton-like interactions create new waveguide structures.