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Développement de l'émetteur hyperfréquence d'un système Lidar-Radar pour des applications optiques marines

Abstract : The Lidar Radar technique is commonly used for submerged target detection in shallow waters less than a few tens of meters. This technique is based on sending a modulated signal, associated with a bandpass filter around the modulation frequency after detection. This technique requires an intense blue-green optical signal modulated at radar frequencies. We present in this thesis new modulator architectures perfectly adapted to this technique. The first architecture consists of an external cavity with an intracavity SHG stage. This architecture is coupled to an infrared picosecond laser source (1064 nm). The results showed that this modulator makes it possible to generate a green signal (532 nm), intense (5 mJ) and stable in frequency. Thanks to the source used, the signal modulated at the output of the transmitter (laser source and modulator) lasts only a few nanoseconds. This makes it possible to use the "range-gating" method to precisely locate the target.Nevertheless, this device has the disadvantage of a fixed bandwidth. We have therefore developed a second architecture of the modulator, allowing to easily tune the bandwidth of the transmitted signal. This configuration is based on the polarimetric behavior of the optical components in order to change the bandwidth of the signal. We have shown that this modulator can deliver , an intense signal (up to 2.9 mJ), short (a few nanoseconds), at 532 nm, modulated at mirowave frequencies, stable in frequency and tunable in bandwidth.
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Nour Alem. Développement de l'émetteur hyperfréquence d'un système Lidar-Radar pour des applications optiques marines. Optique / photonique. Université de Bretagne occidentale - Brest, 2019. Français. ⟨NNT : 2019BRES0013⟩. ⟨tel-02426242⟩

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