TDLAS a laser diode sensor for the in situ monitoring of H2O, CO2 and their isotopes in the Martian atmosphere

High spatial resolution laser cavity extinction and laser-induced incandescence in low-soot-producing flames

“…SNR issues can be improved by using multi-pass cells, often at the expense of spatial resolution [27][28][29][30]. As alternatives, cavity ring-down spectroscopy (CRDS) [14,[31][32][33][34][35][36] and multi-pass tunable diode laser absorption spectroscopy (TDLAS) absorption methods [37][38][39][40][41][42][43][44][45][46] have been developed to obtain high SNR when concentrations are very small.…”

Laser diode spectroscopy of the H2O isotopologues in the 2.64μm region for the in situ monitoring of the Martian atmosphere

“…A near-infrared diode laser spectrometer, called TDLAS [1] which stands for ''tunable diode laser absorption spectrometer'', is presently under development in our laboratory with the support of the CNES and the CNRS. The sensor aims at providing highly-resolved in situ measurements of H 2 O and CO 2 isotopologues in the Martian lower atmosphere.…”

“…The principle of TDLAS is rather simple [1]; the laser beam is propagated in the open atmosphere over a 1-m absorption path length, where it is partially absorbed by ambient molecule. The amount of absorbed laser energy can be related to the molecular densities using the Beer-Lambert law and a simple molecular model.…”

“…Assuming an absorption path length of 10 m, the absorption depth is of the order of a few 10 À4 . The detection limit of the differential detection scheme developed for the TDLAS spectrometer [1,4] is 10 À5 expressed in absorption units, for a measurement time of a few seconds, which makes it possible to detect in situ H 2 O isotopes. Nevertheless, the detection of the H 2 O isotopes requires us to expand the absorption path length from 1 to 10 m, which can be done using a compact optical multipass cell [7] but makes the TDLAS sensor heavier ($1.5 kg).…”

Faraday modulation spectrometry of nitric oxide addressing its electronic X^2Π−A^2Σ^+ band: II experiment

“…For robust implementation, it often uses Distributed Feedback Lasers (DFB) to address various overtone bands and incorporates Wavelength Modulation Spectrometry (WMS) for reduction of noise [16][17][18][19][20]. Although this technique is versatile and regularly used for detection of a number of species under various conditions [12][13][14][15][21][22][23][24][25][26][27], its detectability is not yet sufficient for in-situ detection of NO [28][29][30][31][32][33][34], primarily caused by a combination of low transition probabilities of the overtone bands in 3 the infrared (IR) region and a lack of reliable diode lasers producing light in the wavelength regions of these bands. In addition, the overtone bands are susceptible to spectroscopic interferences from concomitant species, which can hamper quantitative assessments.…”