Accueil > RECHERCHE > Matériaux et optique > Equipe OML > Activités de recherche > Axis 1 : Matériaux Instrumentation Laser (MIL)

Mid-IR source and energy conversion processes for all-optical IR sensors

par BRAUD Alain - publié le , mis à jour le

Fundings : OPTIGAS (ANR 2016-2020 – coordination) DEMETO (Maturation 2018-2020 – coordination), TOUTOPTIK (BPIFrance, 2015-2017 – coordination) COPTIK (ADEME, 2014-2017 - partner)

PhD and Post-doc involved : F. Starecki, I. Afienne, A.L. Pelé
Collaborations : ISCR Rennes, IDIL Lannion, BRGM

We develop prototypes for all-optical gas detection using rare earth doped chalcogenide fibers in collaboration with the ISCR of Rennes. These detectors have the advantage of allowing in-situ and real-time analysis of the gas concentration. The use of an original concept of frequency conversion from infrared to visible allows the use of commercial optical fibers to transport the detection signal. This detector thus allows remote sensing over long distances between the gas detection zone and the data analysis zone. A first project funded by ADEME made it possible to build an efficient prototype for detecting CO2. The ANR OPTIGAS and the DEMETO maturation project, both coordinated by MIL, aim to develop this same type of detection for dangerous gases around 8 µm and for methane respectively.
This detection principle can be applied to the detection of many gases having infrared (IR) absorption bands MWIR (3-5 µm) or LWIR (7-10 µm). The detection of these gases is done using the efficient IR emissions of rare earth ions (RE) incorporated into chalcogenide glasses, which are well known for having low phonon energies. For instance, the all-optical carbon dioxide sensor developed at CIMAP is based on a 4.3 µm infrared source which probes the absorption of CO2 using a fluorescent chalcogenide fiber GaGeSbS doped with Dy3+. After the partial absorption of the 4.3 µm signal by CO2, a wavelength conversion of 4.3 µm to 808 nm is implemented using excited state absorption mechanisms (EEA) in Er3+ doped GaGeSbS glasses or fibers. This wavelength conversion then allows the use of commercial silica fibers to transport the converted signal at 808 nm. This all-optical sensor with a sensitivity of a few hundred ppm can be deployed over a kilometer distance, which makes this tool suitable for field operations.
Finally, the photon conversion principle used in this gas sensor could be implemented in multiple applications requiring the detection of infrared signals using visible or near infrared detectors with higher sentivity than mid-infrared detectors used within the current project.