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Spectroscopie femtoseconde cohérente bidimensionnelle dans l'infrarouge

Abstract : Non-linear femtosecond spectroscopy is the optical analog of multidimensional nuclear magnetic resonance. We report on a new class of optical multidimensional Fourier transform spectroscopy associated with a visible (800 nm) excitation / infrared (10 µm) emission configuration, in which the emitted field results from second-order optical nonlinearities. This technique enables the mapping out of the infrared emission of the sample along two frequency axes : one in the infrared spectral domain, the other in the visible (electronic transition) spectral domain. The retrieved map allows correlation of infrared spectra and Raman spectra at a microscopic level and at the lowest order of non-linearity. This technique is especially well suited to study molecules and semiconductor nanostructures. This configuration is demonstrated on a phase-matched sample, whose effective second order response Xi(2)(−omega2,omega3) is known, by means of the coherent measurement of the midinfrared (15-40 THz) field emitted after a femtosecond visible (340-400 THz) 16 fs phaselocked pulse pair excitation. We further extended our demonstration of two-dimensional Fourier transform visible-infrared spectroscopy to the measurement of the full spectral dependence of the non-linear response of a more complex sample of asymmetric quantum wells. The observed response exhibits the construction of a sum rule over the valence states. Along the way, results on pulse-shaping in the mid-infrared have been obtained : We demonstrate broadband infrared pulse shaping by means of difference frequency mixing of two visible phase-locked linearly chirped pulses in GaAs . The experimental developments reported in this work (portable setup Plug n'Play 2, all digital control of time delays and phase locking, self-referenced detection, long range piezoelectric transducer replacing step motor) are crucial for our experiments where, as the response function of the sample under study is retrieved via double Fourier transform, the time axes of the experiment must be carefully calibrated and locked. These developments can be applied to all multidimensional Fourier transform experiments and to many optical spectroscopy experiments using pulse sequences for excitation or detection of the signal field.
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Contributor : Nadia Belabas <>
Submitted on : Friday, November 19, 2004 - 12:20:16 PM
Last modification on : Thursday, November 7, 2019 - 3:54:03 PM
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Nadia Belabas. Spectroscopie femtoseconde cohérente bidimensionnelle dans l'infrarouge. Physique Atomique [physics.atom-ph]. Ecole Polytechnique X, 2002. Français. ⟨tel-00007455⟩

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