Bertrand Parvitte

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.

Tunable diode laser spectrometer apparatus function

Abstract Lead-salt diode lasers (TDL) are extensively used in experiments involving absorption line intensity and absorption linewidth measurements. In these experiments, the finite TDL linewidth poses a problem and it is necessary to know precisely the TDL lineshapes and linewidths. For this purpose, three methods are used: records of spectra at low pressure, etalon fringes analysis and heterodyne measurements.

Line profile study of the R6 multicomponent of CH 4 around 1.6 µm for the French-German climate mission MERLIN

In the framework of research program MERLIN, GSMA and LISA report the development of a spectrometer especially dedicated to the measurement of high-resolution spectroscopic parameters of R6 multicomponent of methane in the 1.6 µm region.

Coherent quantum cascade laser array at 8.2 μm in extended-cavity system

In the framework of research program “COCASE”, GSMA and III-V lab report the development of a monolithic quantum cascade array emitting at 8.2 μm mounted in an external-cavity system in order to obtain wide tunability.

A coherent quantum cascade laser array for high power emission

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.

Measured and calculated parameters of water vapor line contour induced by hydrogen and helium pressure in the 1.4 μm region

A near-infrared diode laser spectrometer was used under laboratory conditions to measure the H2O line strengths and shifts by H2 and He pressure near 1.39 μm. The hydrogen and helium broadened half-widths and shifts were measured for 5 transitions. These lines from the v1 + v3 and 2v1 bands were selected because they are used for the “Spectrometre a diodes lasers” SDLA spectrometer (France) and to complete a set of isolated and quite strong lines with different J parameters. The experimental and calculated data are compared based on the semiempirical approximation in the absorption line broadening and shift. The helium pressure-induced shift coefficients and the hydrogen pressure-induced shift coefficients have opposite signs.