QUantum cascade Infrared lasers GAs Remote DEtection – QUIGARDE

The remote detection of gaseous compounds is a part of innovative technologies for the detection of gaseous compounds, whether it is in the civil domain for the atmospheric applications or in the field of the defense for the detection of hazardous materials. This last point is the object of one of the priorities of the Policy and of the Scientific Objectives 2011-2012 of the axis “Photonique” of the “Direction Générale de l’Armement”.

This project aims to demonstrate in laboratory the performances of a heterodyne spectrometer using Quantum Cascades Lasers (QCL) emitting around 10 µm. It also has for objective to optimize these performances via the optimization of laser sources used as local oscillator of the device.

The infrared heterodyne detection is a technique that was mainly developed to improve the detectivity of the infrared detectors, in particular in the window 8-12 µm. This technique was associated for a long time strictly for gas lasers and for cooled detectors. Fields of application were mainly the astrophysical and atmospheric studies. Few other applications were able to be envisaged because of the complexity of implementation and the dimensions of this type of instruments. Yet the recent progress in the field of lasers with semiconductors (such as the QCL which cover a big part of the infrared spectrum) and detectors (increase of the temperature of functioning) allows to envisage new developments and new applications for the infrared heterodyne detection, for example for the detection and the remote identification of molecules of atmospheric interest, such as pollutants. This technique is perfectly mastered by the partner 1 of the present project.

The main assets of the heterodyne detection concern the spectral and directional selectivity of the instrument. Besides, this method allows obtaining a limit in terms of sensibility of the order of some ppm.m. It is applicable in the civil domain to the molecules of atmospheric interest such as ozone and carbon dioxide and for the military domain in the detection of hazardous materials.

In spite of the progress of the characteristics of the QCL, their price remains at present prohibitive with only some companies in the world capable of supplying this type of device. Besides, it remains impossible to try to optimize their characteristics. Yet, the performances of the heterodyne spectrometer are intrinsically connected to the performances of the laser, in particular at the level of the noises such as phase noise and amplitude noise. The present project thus has for objectives:
- - to develop QCL around 10 µm by the III-V lab (partner 2 of the project);
- - to test them and to optimize them by the LPL (partner 3 of the project);
- - to integrate them into a heterodyne spectrometer by the GSMA (partner 1 of the project).