All OPTIcal hazardous GAs Sensor in infrared – OPTIGAS

The originality of our approach is to develop an all- optical method, allowing in situ analysis (remote) , in real time, and for continuous monitoring in a wide range of concentrations from 1 ppm to 100%. This wide range of detection is possible in particular with the aid of a detection cell of variable length, which will be tailored for the target concentration range, but also by exploiting the large wavelength spectrum that can provide the emission of rare-earth ions for a differential measurement. Furthermore, we want to demonstrate with this project the frequency conversion from the middle-IR ( MIR) to the near-IR or visible to physically separate the sensor and the electronics of the optical head positioned in the sensitive area to be analyzed. The principle of this all-optical sensor, which has both high sensitivity and a wide detection range, will be validated first in band II before being transposed to band III, in particular for the remote detection of toxic gases. To do this, different types of IR active materials will be synthesized within the consortium. Selenides and sulfides fibers doped with different rare earth ions will be fabricated as a first step for gas detection in band II. More importantly, the ambitious development of active materials for Band III will be a crucial step in this project. Thus, fibers made from rare-earth doped telluride glasses will be manufactured as well as rare-earth doped chloride and bromide crystals. These materials will be used as IR sources and as frequency converters to convert IR radiation into visible or near-IR radiation. The originality of the proposed sensor therefore lies in this conversion process of the IR signal into visible or near IR signal that can deport the useful signal via silica fibers and thus obtain an «all-optical« sensor in band III immune to electromagnetic interferences and usable for remote measurements at sites considered dangerous or inaccessible to humans.

Major achievements of the project at mid-term:

- Production of an all-optical sensor in Band II (at 4.3µm for CO2): (Task 2)
For the first time, we confirmed the idea of ??the all-optical sensor presented in the ANR OPTIGAS project by manufacturing an all-optical sensor prototype in band II at 4.3µm which was validated by calibrated gas measurements.

- Fibers based on high quality selenide glasses: (task 1)
The substitution of selenium sulfide in a controlled proportion allowed us to improve the incorporation of the rare earths and the quality of the fibering in a very substantial way, enabling us to reach higher concentrations of rare earths and comfort in terms of resistance to the crystallization of the fibers.

- Fiber emitting around 7.8µm: (Task 3.1)
For the first time, the OPTIGAS consortium synthesized and characterized a rare earth doped chalcogenide fiber emitting around 7.8µm. Such a result paves the way for the detection of gas in band III.

The promising results obtained in Task 2 in Band II will be used directly in Task 3 (Band III) to identify the key characteristics of both the IR source, the converter and the sensor as a whole. Task 3 deals with the characterization of the IR source and frequency conversion in band III (8 - 10 µm). Some of the characterizations of the effect of frequency conversion in band III will be done at ONERA taking advantage of different IR sources and expertise on the IR optical devices available to ONERA.
The fourth and final task will take place during the last year of the project and will be aimed at demonstrating the principle of the all-optical sensor in Band III.

1. “Dy3+ doped GeGaSbS fluorescent fiber at 4.4 µm for optical gas sensing: Comparison of simulation and experiment” A.L. Pelé, A. Braud, J.L. Doualan, F. Starecki, V. Nazabal, R. Chahal, C. Boussard-Plédel, B. Bureau, R. Moncorgé, P. Camy, Optical Materials, Vol.61, (2016), p.37
2. Tb3+ doped Ga5Ge20Sb10Se(65-x)Tex (x = 0-37.5) chalcogenide glasses and fibers for MWIR emission, N. Abdellaoui, F. Starecki, C. Boussard-Pledel, J-L. Doualan, Y. Shpotyuk, A. Braud, E. Baudet, P. Nemec, F. Cheviré, B. Bureau, P. Camy, V. Nazabal, Optical Material Express soumis .
3. Carbon monoxide, dioxide and methane sensing using Pr3+ doped Ga5Ge20Sb10Se65 fibers, F. Starecki, J. Ari1,, C. Boussard-Plédel, B. Bureau, Y. Ledemi, Y. Messaddeq and V. Nazabal, soumis, Sensors and actuators B

5 Invited Talks:
1. “Photon conversion in the mid-infrared for gas sensing”, A. Braud et al. DPC, Paris (2016),
2. “Rare-earth doped chalcogenide glasses for mid-IR luminescence”, V. Nazabal, et al., PRE 2016, Greenville USA, (2016).
3. “Rare-earth doped materials for IR gas sensing and IR to visible conversion” A. Braud et al., ICALSTM, India (2016).
4. “Chalcogenide glass waveguides for infrared light sources and sensors”, J.L. Adam et al., XI Brazilian Symposium on Glass and Related Materials, Brazil, (2017).
5. J. Armougom, Q. Clément, J.-M. Melkonian, J.-B. Dherbecourt, M. Raybaut, A. Grisard, E. Lallier B. Gérard, B. Faure, G. Souhaité, A. Godard, « Single-frequency tunable long-wave infrared OP-GaAs OPO for gas sensing, » SPIE Photonics West 2017, (San Francisco, USA, 28 juin–2 février 2017), papier 10088-33 .

Patent :
N° 1659603, Verres de chalcogénures (spécifiques aux dopages terres rares) Virginie NAZABAL, Julien ARI, Florent STARECKI, Catherine BOUSSARD-PLEDEL

Detection of toxic gases is of prime importance for the security of sensitive sites and public places . Gas detection can be efficiently achieved using their absorption bands in midwave(3- 5µm ) e.g to 3.4µm (vibrational modes of CH bonds) , and even more selectively in longwave ( 8 - 12µm ) , where can be detected for example sarin gas at 9.8µm . The OPTIGAS project aims to develop an all-optical fiber sensor for Band III. The principle of this sensor is very versatile and can be adapted to various kinds of gases having spectroscopic signatures in atmospheric transparency windows (bands II and III ). The originality of our approach is to develop an all- optical method, allowing in situ analysis (remote) , in real time, and for continuous monitoring in a wide range of concentrations from 1 ppm to 100%. This wide range of detection is possible in particular with the aid of a detection cell of variable length, which will be tailored for the target concentration range, but also by exploiting the large wavelength spectrum that can provide the emission of rare-earth ions for a differential measurement. Furthermore, we want to demonstrate with this project the frequency conversion from the middle-IR ( MIR) to the near-IR or visible to physically separate the sensor and the electronics of the optical head positioned in the sensitive area to be analyzed. This all-optical sensor will enable a remote detection without severe limiting distance between the sensing area and the data analysis location. The principle of this all-optical sensor, which has both high sensitivity and a wide detection range, will be validated first in band II before being transposed to band III, in particular for the remote detection of toxic gases. To do this, different types of IR active materials will be synthesized within the consortium. Selenides and sulfides fibers doped with different rare earth ions will be fabricated as a first step for gas detection in band II. More importantly, the ambitious development of active materials for Band III will be a crucial step in this project. Thus, fibers made from rare-earth doped telluride glasses will be manufactured as well as rare-earth doped chloride and bromide crystals. These materials will be used as IR sources and as frequency converters to convert IR radiation into visible or near-IR radiation. The originality of the proposed sensor therefore lies in this conversion process of the IR signal into visible or near IR signal that can deport the useful signal via silica fibers and thus obtain an "all-optical" sensor in band III immune to electromagnetic interferences and usable for remote measurements at sites considered dangerous or inaccessible to humans.