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Mise en forme spectrale et temporelle de sources optiques infrarouges par mélange non-linéaire à trois ondes

Abstract : Because they use a resonant process, lasers are often hindered by the small number of available wavelengths and their narrow tunability. Fortunately, nonlinear optics allows to go beyond these limitations by doing frequency conversion in a non resonant way. It is now used in optical parametric oscillators (OPOs) to cover the whole optical spectrum with a wide tunability. However, OPOs display unique properties : three coupled waves with different frequencies and group velocities, a power and phase dependent amplification, and no energy storage. In this work we show that these properties lead to new designs of nonlinear optical sources. We begin with an OPO with increased efficiency, implementing two KTA crystals pumped at 1,064 μm in the nanosecond regime. We then study the possibility of generating short pulses directly in a cw-pumped OPO. We show for the first time that active modelocking in an OPO is possible in the steady-state regime. We then propose to implement passive modelocking by a saturabler absorber in an cw-pumped OPO where there is a strong group velocity mismatch between the signal and the pump. Finally, we adress optical sources including a laser medium and a nonlinear crystal. We build a nonlinear mirror using a PPLN crystal and insert it in a Cr:ZnSe laser to produce picosecond pulses by passive modelocking. We also discuss the possibility of including an OPO inside a cw laser, to produce short tunable pulses in the mid-infrared.
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https://pastel.archives-ouvertes.fr/tel-00318682
Contributor : Jean-Michel Melkonian <>
Submitted on : Thursday, September 4, 2008 - 4:09:35 PM
Last modification on : Friday, October 23, 2020 - 4:52:13 PM
Long-term archiving on: : Thursday, June 3, 2010 - 8:35:37 PM

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Jean-Michel Melkonian. Mise en forme spectrale et temporelle de sources optiques infrarouges par mélange non-linéaire à trois ondes. Physique Atomique [physics.atom-ph]. Ecole doctorale de l'Ecole Polytechnique (EDX) - ED 447, 2007. Français. ⟨tel-00318682⟩

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