Laser spectroscopy technique :
By means of the coupling of a laser to a high finesse optical cavity, the effective absorption length is enhanced up to tens of kilometers, while the actual cavity length is only about 50 cm allowing for a compact set-up for in-situ measurements. Our group at LIPhy has developed an original technique called Optical Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) that relies on the sensitivity of a semi-conductor laser to optical feedback [1]. OF-CEAS, enables the design of a compact instrument with very high detection sensitivity and very high molecule specificity. Additional advantages are that the method does not require routine calibration with certified gas mixtures and that the resulting robust instruments can be operated by non-specialists.
NO analyzer in the mid infrared region (MIR) :
The NO analyzer operates with an Interband Cascade Laser (ICL) that became recently available in the mid-infrared region (MIR) where strong absorption lines can be addressed, allowing to obtain a sub-ppb sensitivity. Nonetheless, addressing large intensity absorption lines, optical saturation of the molecular transitions has to be accounted for.
Internship objective :
According to the duration of the internship, the student will be in charge of different studies required prior to the Antarctica campaign. She/he will perform an in depth study of optical saturation effects in OF-CEAS analyzers that operate in the MIR. A model will be developed and different analyzers will be available for data acquisition. Additionally, the student will characterize the absolute accuracy of the instrument at very low concentration (subppb) by comparison with another NO detector (chemiluminescence based instrument) and with a calibrated dilution gas line.
Expected skills :
The candidate will have knowledge of optics, lasers and spectroscopy and an interest in modeling and instrumentation.
Supervisor :
Irène VENTRILLARD irene.ventrillard@univ-grenoble-alpes.fr
http://www-liphy.ujf-grenoble.fr/-LAME
[1] L. Richard, D. Romanini, I. Ventrillard, Sensors, 18, 1997 (2018).
[2] R. Grilli, M. Legrand,, A Kukui, G. Méjean, S. Preunkert, D. Romanini, Geophys. Res. Lett., 40, 791 (2013) -