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

Optical Coherence Spectro-Tomography by all-Optical Depth-Wavelength analysis

Current spectroscopic optical coherence tomography (OCT) methods rely on a posteriori numerical calculation. We present an alternative for accessing optically the spectroscopic information in OCT, i.e. without any post-processing, by using a grating based correlation and a wavelength demultiplexing system. Conventional A-scan and spectrally resolved A-scan are directly recorded on the image sensor. Furthermore, due to the grating based system, no correlation scan is necessary. In the frame of this paper we present the principle of the system as well as first experimental results

Stable mode-locked operation of a low repetition rate diode-pumped Nd : GdVO4 laser by combining quadratic polarisation switching and a semiconductor saturable absorber mirror

International audienceIn this paper, we present the mode-locked operation of an ultrarobustly stabilised Nd:GdVO4 laser with low repetition rate by combining quadratic polarisation switching and a semiconductor saturable absorber mirror (SESAM). In addition, similar experiment was also done with Nd:YVO4. For Nd:GdVO4, 16-ps pulses at 1063nm with a repetition rate of 3.95MHz have been obtained for a laser average output power of 1.4W. For Nd:YVO4, the performance was 2.5W of average power for15-ps pulses at 1064nm. Moreover, we demonstrate experimentally the advantage of combining these two passive mode locking techniques in terms of stability ranges. We show how the dual mode-locking technique is crucial to obtain a stable and long-term mode-locked regime in our case of a diode-pumped Nd:GdVO4 laser operating at low repetition rate and more generally how this dual mode-locking technique improves the stability range of the modelocked operation giving more flexibility on different parameter

REFROIDISSEMENT MOLECULAIRE INDUIT PAR CHAMP ELECTRIQUE ; MISE EN EVIDENCE PAR SPECTROSCOPIE NON LINEAIRE CARS

National audienceNous avons montré qu'un refroidissement moléculaire pouvait être induit par un champ électrique statique appliqué à des molécules non polaires d'huile de paraffine. Cet effet a été mis en évidence grâce à une mesure de spectroscopie CARS (Coherent Anti-Stokes Raman Scattering). De manière complémentaire, l'exposition de molécules à un champ électrique permet de contrôler leur orientation et ainsi améliorer ou diminuer l'amplitude de leur signature vibrationnelle

Efficiency of dispersive wave generation in dual concentric core microstructured fiber

We describe the generation of powerful dispersive waves that are observed when pumping a dual concentric core microstructured fiber by means of a sub-nanosecond laser emitting at the wavelength of~1064 nm. The presence of three zeros in the dispersion curve, their spectral separation from the pump wavelength, and the complex dynamics of solitons originated by the pump pulse break-up, all contribute to boost the amplitude of the dispersive wave on the long-wavelength side of the pump. The measured conversion efficiency towards the dispersive wave at 1548 nm is as high as 50%. Our experimental analysis of the output spectra is completed by the acquisition of the time delays of the different spectral components. Numerical simulations and an analytical perturbative analysis identify the central wavelength of the red-shifted pump solitons and the dispersion profile of the fiber as the key parameters for determining the efficiency of the dispersive wave generation process.Comment: 11 pages, 12 figure

Picosecond polarized supercontinuum generation controlled by intermodal four-wave mixing for fluorescence lifetime imaging microscopy

International audienceWe present the generation of a picosecond polarized supercontinuum in highly birefringent multimodal microstructured fiber. The initial steps of the spectral broadening are dominated by intermodal four-wave mixing controlled by the specific fiber design. Using a low repetition rate ultra-stable solid state laser, a pulse train well-suited for versatile time-domain fluorescence lifetime imaging applications is obtaine

Visible supercontinuum generation controlled by intermodal four-wave mixing in micro-structured fibre

International audienceWe present an experimental and numerical study of supercontinuum generation extended in the visible part of the spectrum by using a selective optical coupling of the pump wave in the largely anomalous dispersion regime. The broadband frequency generation is induced by an initial four-wave mixing process that converts the pump wave at 1064 nm into 831 nm anti-Stokes and 1478 nm Stokes wavelengths. Phase matching is ensured on such a large frequency shift thanks to a microstructured multimodal fiber with a specific design. Continuum generation is therefore enhanced around the two generated sideband

Identification of intracellular squalene in living algae, Aurantiochytrium mangrovei with hyper-spectral coherent anti-Stokes Raman microscopy using a sub-nanosecond supercontinuum laser source

We applied hyper-spectral coherent anti-Stokes Raman scattering imaging to intracellular lipid identification in living microalgae, Aurantiochytrium mangrovei 18W-13a. Two different lipids, squalene and triacylglycerol, were found inside living cells with clear vibrational contrast. Based on the endogenous lipid band as a result of the cis C[DOUBLE BOND]C stretch vibrational mode, squalene and triacylglycerol were clearly distinguished in different intracellular areas. In particular, squalene was detected solely in vacuoles as lipid particles, which was also supported by electron microscopy

Backward multiplex coherent anti-Stokes Raman (CARS) spectroscopic imaging with electron-multiplying CCD (EM-CCD) camera

A multiplex CARS imaging system, equipped with an EM-CCD camera, was developed to improve the sensitivity of backward CARS imaging in biological analysis using an inverted microscope. The signal-to-noise ratio was improved by a factor of ca. 3 compared to a conventional CCD mode through the use of EM gain. When imaging epithelial cells in the backward CARS configuration, intracellular organelles such as lipid droplets and nuclei were spectroscopically identified with an exposure time of only 100 ms/pixel.</p