Sources paramétriques optiques pour la détection de gaz à distance dans l'infrarouge lointain

摘要

To ensure stand-off detection of gaseous chemical species in the atmosphere by active infrared spectrometry, a coherent source emitting a widely tunable narrow spectral linewidth beam with good quality and high energy is required. Parametric sources based on second order non linear optics are the only technological solution meeting all these requirements in the nanosecond regime. However, their development in the 6-16 µm spectral range (including the 8-12 µm atmospheric transparency window), which contains several absorption lines of hazardous chemicals and explosives, has not been sufficient yet due to technological difficulties. In this work, we show how to address this challenge by setting up the first pulsed single-frequency optical parametric oscillators emitting in the 8-12 µm range, based on the doubly resonant Nested Cavities architecture (NesCOPO). We also propose a new kind of very compact OPO with amazing tunability properties (Sheet OPO). Finally, by carrying out stand-off detection of ammonia vapor and optical parametric amplification experiments, we show how these sources can be used as the core element of operational systems for long range stand-off detection of hazardous gases in the atmosphere.