Frequency-dissymmetric parametric sideband generation in a microstructured fiber

International audienceWe experimentally demonstrate the nonlinear generation of frequency-dissymmetric sidebands by injecting picosecond pump pulses inside the fundamental mode of a silica-core photonic crystal fiber in its normal dispersion regime. A systematic analysis highlights the fact that this phenomenon is based on the combination of the two major nonlinear effects occurring inside the fiber: self-phase modulation and degenerate four-wave mixing

Bulk Photorefractive Semiconductors

International audienceInconn

Saturation of the Raman amplification by self-phase modulation in silicon nanowaveguides

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.Comment: Accepted for publications in Applied Physics Letter

Efficient Raman converter in the yellow range with high spatial and spectral brightness

International audienceWe present a Raman converter emitting at 583 nm on the second Stokes order of a line of propan-2-ol pumped by a microlaser at 532 nm in the sub-nanosecond regime. We used a mixture of liquids to adapt the transmission band of a photonic bandgap fiber. The internal conversion efficiency is 67% in photon numbers, and the output power is 1.06 mW, corresponding to a maximum peak power of 338 W. The beam delivered by the converter presents a Gaussian spatial structure and a high spectral brightness, typically more than five times higher than supercontinuum sources in this spectral range

Light localization induced enhancement of third order nonlinearities in a GaAs photonic crystal waveguide

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 TPA generated free-carriers. A theoretical model has been established that shows very good quantitative agreement with experimental data and demonstrates the important role that group velocity plays. These observations give a strong insight into the use of PCWs for optical switching devices.Comment: 6 page

Stimulated Raman scattering with large Raman shifts with liquid core Kagome fibers (Orale)

International audienceStimulated Raman scattering in photonic band gap liquid filled fibers is known to be an attractive technique for manufacturing efficient wavelength converters. However the possible frequency shifts are limited by the spectral bandwidth of these fibers. We experimentally demonstrate that Kagome fibers allow to greatly enlarge these shifts

BAUTISTA, ANA E HIJO [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Heterodyne Detection of Ultrasound from Rough Surfaces Using a Double Phase Conjugate Mirror

Ultrasonic excitation of a solid sample (optically opaque) can be detected by directing a laser beam at one of its surfaces. Surface motion causes a transient phase shift upon the scattered light, which has to be demodulated into an intensity variation prior to its detection by a photodetector. Classical reference beam interferometry (homodyne or heterodyne) is a well-known technique for performing this demodulation. It is characterized by a broad detection bandwidth, but is, following the antenna theorem [1], essentially limited to the detection of one speckle, when used on rough surfaces. In order to circumvent this limitation (i.e., in order to increase the étendue of the interferometer), two different approaches for adapting the signal and reference wavefronts have been considered. The first approach proceeds by creating a reference beam that matched the wavefront of the signal beam. This can be done by using a Fabry-Pérot (FP) [2] which is a self-reference interferometer and means that the reference beam is generated by the signal beam. It can also be done by using two-wave mixing (TWM) in a photorefractive crystal [3,4]. In this case, the reference beam is created by the diffraction of a plane wave pump beam by the hologram written by both pump and signal beams. Alternatively the signal beam wavefront can be adapted to the reference wavefront, which requires, since the reference beam can usually be approximated by a plane wave, the transformation of the speckled beam to a beam with a plane wavefront. Devices using externally pumped [5] or self-pumped phase conjugate mirrors (SPCM) [6] have been reported