NONLINEAR PULSE SHAPING FORCOHERENT RAMAN MICROSCOPY Esben Ravn Andresen 1 , John Dudley 2 , Dan Oron 3 , Christophe Finot 4 and Hervé Rigneault 1 1 Institut Fresnel, MOSAIC - CNRS UMR 6133, Universités Aix-Marseille III, Ecole Centrale Marseille - Domaine Universitaire de Saint Jérôme 13013 Marseille, France 2 Laboratoire d'Optique P.M. Duffieux, Institut FEMTO-ST CNRS, 16 Route de Gray, 25030 Besançon Cedex, France 3 Dept. of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel 4 Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS-Université de Bourgogne, 9 Av. A.Savary, BP 47870, F-21078 DIJON Cedex, France Email : herve.rigneault@fresnel.fr KEY WORDS : Nonlinear optics in optical fibre, Red shifting soliton, Spectral compression, Nonlinear microscopy, Coherent Raman microscopy Nonlinear photonic-crystal fibers (PCF)s are efficient frequency converters, most dramatically demonstrated in supercontinuum generation. Nonlinear pulse shaping is a new and more deterministic approach to frequency conversion and consists in amplitude and phase shaping the laser pulse prior to launching it into a highly nonlinear PCF with the aim of generating light only in a certain frequency range. This can be done by shaping the laser pulse into a train of weak pulses, each optimized to form a fundamental soliton in the PCF. In the PCF, each soliton redshifts by ∆ν (which is dependent on the initial peak power P) and slows down due to fibre dispersion. Coherent anti-Stokes Raman spectroscopy (CARS) has been demonstrated using red-shifting soliton as a Stokes beam [1], nevertheless the output extracted power has been limited due to the inherent low power carried by a single soliton. In this work we use nonlinear pulse shaping to increase the spectral brightness of red shifting soliton to perform coherent Raman spectroscopy and microscopy. Both CARS and stimulated Raman scattering (SRS) are investigated and demonstrated in test samples. Using nonlinear pulse shaping it is also possible to perform spectral compression to generate narrow band spectral line suitable for coherent Raman [2]. This is the goal of this presentation to show the assets of nonlinear pulse shaping as an alternative powerful technique to generate a variety of output frequency shaped light pulses suitable for coherent Raman imaging. Oscillator 4f Pulse shaper 0.5 50x Nonlinear PCF 0.5 50x To microscope Oscillator 4f Pulse shaper 0.5 50x 0.5 50x Nonlinear PCF 0.5 50x 0.5 50x To microscope Figure: Principle of a nonlinear pulse shaper. A 4f pulse shaper and a highly nonlinear fiber generate a variety of controllable output light pulses suitable for coherent Raman spectroscopy and microscopy. References [1] E. R. Andresen, V. Birkedal, J. Thogersen, S.R. Keiding, ‘Tunable light source for coherent anti-Stokes Raman scattering microspectroscopy based on the soliton self-frequency shift’, Opt. lett. 31, 1328-1330 (2006). [2] E. R. Andresen, J. Dudley, D. Oron, C. Finot, H. Rigneault, ‘Transform-limited spectral compression by self-phase modulation of amplitude shaped pulses with negative chirp’, Opt. Lett., accepted (2011).