Julien Cousin

Diode laser spectroscopy of two acetylene isotopologues (12C2H2, 13C12CH2) in the 1.533 μm region for the PHOBOS-Grunt space mission

Several line intensities of the nu(1) + nu(3)(Sigma(u)(+)) - 0(Sigma(g)(+)) bands of (12)C(2)H(2) and (13)C(12)CH(2) at 1.533 microm have been revised at room temperature. These molecular transitions were selected to measure acetylene within the framework of the Martian space mission PHOBOS-Grunt. In the spectral region ranging from 6518 to 6530 cm(-1), 10 lines of both isotopologues have been analyzed using a high resolution tunable diode laser spectrometer. These transitions are well appropriate to the monitoring of C(2)H(2) by laser absorption spectroscopy with standard telecommunication laser diodes. Both the Voigt and the Rautian models are used to fit the molecular line shape and to provide accurate line strengths. Our data are thoroughly compared to existing database (including HITRAN08) and former experimental measurements.

Continuous-wave quantum cascade lasers absorption spectrometers for trace gas detection in the atmosphere

Mid infra-red absorption spectrometry based on continuous-wave distributed feedback (DFB) quantum cascade laser (QCL) is more and more widely used for trace gas detection and pollution monitoring. The main advantages of this technique are high sensitivity, high selectivity and a potential for extreme compactness. Various examples of trace gas detection for atmospheric detection will be presented in this paper. Commercial QCLs available on the shelves were first implemented. A cryogenic QCL emitting at 6.7 μm was used to demonstrate the detection of water vapor and its isotopes. A room-temperature QCL was then used to simultaneously detect methane and nitrous oxide at 7.9 μm. Recently, we have developed a room-temperature top grating DFB QCL designed around 4.5 μm for the demonstration of N2O detection in the ppb range. Atmospheric applications of these spectrometers will be presented. The improvements of QCL performances make it now possible to develop instruments that are more and more compact and therefore compatible with in situ applications.

Self-induced pressure shift and temperature dependence measurements of CO2 at 2.05μm with a tunable diode laser spectrometer.

By using a high resolution tunable diode laser absorption spectrometer combined with a cryogenically cooled optical multi-pass cell, we have measured the self-induced pressure shift coefficients for 8 transitions in the R branch of the (20(0)1)(III)←(00(0)0)(I) band of carbon dioxide around 2.05μm. This spectral region is of particular interest for the monitoring of atmospheric CO(2) with Differential Absorption Lidars (DiAL). The measurement of these shift coefficients was realized at five different temperatures ranging from 218 to 292K in order to determine their temperature dependence. The results are thoroughly compared to previous values reported in the literature for the (20(0)1)(III)←(00(0)0)(I) band of CO(2). The temperature dependence of the self-induced pressure shifts are reported experimentally for the first time for this specific CO(2) band.

Wavelet Denoising for Infrared Laser Spectroscopy and Gas Detection

After a brief introduction to wavelet theory, this paper discusses the critical parameters to be considered in wavelet denoising for infrared laser spectroscopy. In particular, it is shown that measurement dispersion as well as sensibility can be dramatically improved when using wavelet denoising for gas detection by infrared laser absorption spectroscopy.

Atmospheric Measurements by Ultra-Light SpEctrometer (AMULSE) Dedicated to Vertical Profile in Situ Measurements of Carbon Dioxide (CO2) Under Weather Balloons: Instrumental Development and Field Application

The concentration of greenhouse gases in the atmosphere plays an important role in the radiative effects in the Earth’s climate system. Therefore, it is crucial to increase the number of atmospheric observations in order to quantify the natural sinks and emission sources. We report in this paper the development of a new compact lightweight spectrometer (1.8 kg) called AMULSE based on near infrared laser technology at 2.04 µm coupled to a 6-m open-path multipass cell. The measurements were made using the Wavelength Modulation Spectroscopy (WMS) technique and the spectrometer is hence dedicated to in situ measuring the vertical profiles of the CO2 at high precision levels (σAllan = 0.96 ppm in 1 s integration time (1σ)) and with high temporal/spatial resolution (1 Hz/5 m) using meteorological balloons. The instrument is compact, robust, cost-effective, fully autonomous, has low-power consumption, a non-intrusive probe and is plug & play. It was first calibrated and validated in the laboratory and then used for 17 successful flights up to 10 km altitude in the region Champagne—Ardenne, France in 2014. A rate of 100% of instrument recovery was validated due to the pre-localization prediction of the Météo—France based on the flight simulation software.

Des ballons pour le climat

Depuis trois ans, le Centre national d’études spatiales (Cnes) collabore avec l’Agence spatiale canadienne (CSA-ASC) pour réaliser des campagnes de lâchers de ballons stratosphériques ouverts depuis la base de Timmins en Ontario (Canada). Les ballons emportent dans la stratosphère, jusqu’à environ 40 km d’altitude, plusieurs centaines de kilogrammes d’instrumentation scientifique afin de réaliser des observations dans les domaines de la physico-chimie de l’atmosphère ou de l’astronomie. La campagne StratoScience 2015 organisée du 12 août au 30 septembre a débuté par le vol Climat (figure 1).

Tuneable erbium-doped fibre laser-based spectrometer for trace gas detection in the near infrared

10 D uring the last decade, the need for optical telecommunication, e.g. dynamic DWDM (Dense Wavelength Division Multiplexing) optical networks, has spurred the development of continuous-wave (cw) tuneable lasers in the near infrared (NIR) around 1.55 μm. Today these devices are finding an increasing number of applications, not only in the telecommunication domain but also in high-resolution molecular spectroscopy and atmospheric/ environmental spectroscopy. Gas analysis with tuneable diode laser spectrometry in the NIR wavelength range around 1550 nm is attractive because of the commercial availability of photonic components such as DFB and ECL diode lasers, rare earth doped fibre laser or photodiodes originally designed for the use in fibre-optic communication systems. Their extremely high reliability, defined by industrial telecom standards, their tight specifications and high performances in terms of stable and low-noise operation partially compensates for the major drawback of NIR molecular spectroscopy: vibrational overtone line strengths in the NIR are typically of two to three orders of magnitude lower compared to the fundamental lines in the midinfrared region. Additionally, the availability of low-cost cw lasers with output power in the mW to W range with room temperature operation associated with low-loss silica optical fibres for beam delivery to the measurement location allows a remote operation of the electronics as well as the design of compact and robust gas analysers with a high flexibility in installation and application.

Laser Difference-Frequency Generation in the Mid-Infrared and Applications to High-Resolution Molecular Spectroscopy and Trace Gas Detection

We report on the development of a widely tunable continuous-wave (CW) laser spectrometer based on difference-frequency generation (DFG) in a nonlinear optical crystal, which operates in the mid-infrared (MIR) spectral region of 3-20 mum with a Doppler linewidth limited spectral resolution. The state-of-the-art of CW DFG techniques as well as the applications of the DFG-based laser source to high-resolution molecular spectroscopy and trace gas spectroscopy were presented.

OF-CEAS Detects Leak Rates down to 5·10 -9 mbar.L/s

Leak detection and localization is an issue for facility and population security. The paper shows that low leak rates of methane, down to 5 10-9mbar.L/s, are detected by OF-CEAS technique under atmospheric pressure.

Measurements of Gas Species and the 13 CO 2 / 12 CO 2 Isotope Ratio in a Wood-Based Combustion Emission by Laser Absorption Spectroscopy

We report on the application of a field-deployable instrument based on Telecoms-grade laser to simultaneous measurements of multiple species (H2O, CO, CO2, CH4, C2H2) and the13CO2/12CO2isotope ratio in a wood-based combustion.