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Laser spectrometers based on Quantum Cascade Lasers (QCL) provide good results for gas sensing in terms of sensibility and selectivity thanks to the characteristics of these sources. Distributed feedback (DFB) configuration provides narrow linewidth that enhances selectivity and their emission in the mid-IR enables to reach the fundamental absorption bands of molecules. The main limitation of these sources is their narrow tuning range (∼ 10 cm−1) that prevents from monitoring complex species with broad absorption spectra or realizing multi-gas sensing. To obtain a broader tuning range, one solution consists of QCL DFB array with an arrayed waveguide grating to perform multi-species spectroscopy [1]. A more common technique is to implement the laser in an external cavity system. In GSMA, a commercial Extended-Cavity Quantum Cascade Laser emitting at 10.5 μm has been used to demonstrate photoacoustic gas sensing of heavy molecules such as butane [2] and a lab-made EC-QCL emitting at 7.5 μm was developed for detection of acetone and POCl3 in gas phase [3].

Portable and remote sensing solutions to detect the nature of gases in the air are highly demanded. In particular for instance, for the measurement of fire smoke or uncontrolled discharge on risk sites or on an accident including a vehicle transporting hazardous substances [1]. Spectroscopic-based solutions would need a widely-tunable and powerful mid-infrared compact laser source that could be used on field and scan a large number of species.

The laser group of the Groupe de Spectrometrie Moleculaire et Atmospherique (GSMA, Reims, France) has developed various laser spectrometers for the study of the atmospheres [1]. Based on this technology we developed the same type of instrument for enological studies conducted by the Effervescence team of GSMA. A diode laser detection system for the measurements of gas-phase carbon dioxide (CO 2 ) above a glass of bubbly drink such as champagne has been designed [2]. In champagne and sparkling beverages in general, the progressive desorption of CO 2 dissolved in the liquid phase is responsible for bubble formation. Moreover, dissolved CO 2 may also escape by diffusion at the air-champagne interface. A first step in the understanding of the role of CO 2 was to precisely measure its concentration above champagne glasses, under standard tasting conditions [3]. To address this purpose, many optimizations of the set-up have been realized. First the original 2.68 μm diode laser was coupled to an optical fibre to prevent from atmospheric CO 2 interferences. Then, a second laser emitting around 2 μm was adapted to realize measurements with large concentrations of CO 2 . Finally, the whole set-up, namely the CO 2 -DLS, was driven by a LabView ® program in order to automatically record the temporal evolution of gas-phase CO 2 concentration in one position of the headspace above liquid [4]. A set of data showing the impact of champagne temperature and volume as well as the intensity of effervescence on the release of gas phase CO 2 was realized [5].

In the framework of the ANR project called COCASE, GSMA and III-V Lab develop a coherent quantum cascade laser array to obtain high power emission. This source will be combined to a photoacoustic spectrometer devoted to trace gas detection [1]. In such a spectrometer the sensitivity limit is directly proportional to the laser power.