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Apport de l'optique non linéaire à l'imagerie infrarouge pour la détection de cibles à longue distance

Abstract : There is a wide range of applications in active infrared detection technologies in defense and security. However, the limited range available by these systems limits their developments. Increasing sensors sensitivity is a key milestone to improve this range. Indeed, noise in infrared detectors is much higher than for visible detectors due to some physical and technological issues. The key idea of this manuscript is to use nonlinear optical technologies to convert the infrared signal to detect into the visible spectrum and use all the benefits of silicon based sensors. Recent advances in optical crystals and in pump laser regimes bring renewed interest to upconversion detection for some specific application cases identified in this thesis. A novel and easy method to improve the number of converted modes has been proposed after a careful study of multimode conversion both temporally and spatially. In order to give figures on detection improvement using upconversion, we conducted a theoretical and numerical study of the multimode conversion as well as two sets of experiments. The first one, using conversion in an OP-GaAs crystal and a monodetector addresses mid-infrared spectroscopy applications. The second one addresses active imaging applications for target recognition and identification in the near-infrared. By using a PPLN crystal, the near-infrared image is detected on a low noise CMOS camera. A key milestone of this work is the sensitivity improvement of such a detection. Sensitivities obtained in each experiment are one order of magnitude better than with direct detection using common infrared sensors.
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  • HAL Id : tel-01976357, version 2

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Romain Demur. Apport de l'optique non linéaire à l'imagerie infrarouge pour la détection de cibles à longue distance. Physique [physics]. Sorbonne Université, 2018. Français. ⟨NNT : 2018SORUS166⟩. ⟨tel-01976357v2⟩

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