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Infrared Photonic and Sensors

Infrared Photonic and Sensors

The glasses and ceramics group presents an important knowledge of exotic ceramics and glasses, for example: fluorides, phosphates, and chalcogenides. In the past decades, our team has developed a great experience of chalcogenide ceramics and glasses, in their synthesis, purification, their shaping, and also the study of their optical properties. The chalcogenide glasses and fibers are transparent in the mid-IR range, where the infrared fingerprints of molecular species can be detected.

In this context, the main goal of this theme: Infrared photonics and sensors is to achieve innovative high optical quality infrared ceramics, glasses, thin film and fibers, in order to develop new generation of infrared spectroscopy methods and systems. It can be noted that in the visible spectral range, the silica fibre technology permits the realisation of deported systems for imaging and/or spectroscopy. In the mid infrared, these technologies do not exist. For wavelengths longer than 5 µm, among glass materials, only the chalcogenide fibres are still transparent.

This theme of research is divided in different parts as the following: Optical fibers and microstructured optical fibers, infrared ceramics, thin films and waveguides, New Generation of mid-IR sources and Mid-IR spectroscopy.

Optical fibers and microstructured optical fibers

Optical fibers and microstructured optical fibers

The glasses and ceramics group has developed a drawing tower specially designed for drawing soft glass fibers until 900-1000°C and more particularly designed for drawing chalcogenide fibers. Single index fibers, step index fibers and microstructured optical fibers are examples of optical fibers that can be prepared and studied in our lab. In addition, before drawing, high optical quality glasses have to be obtained. In this context, important researches are devoted to the purification of the raw materials and the glasses. Those studies are essential in order to obtained high transmission optical fibers.

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Infrared ceramics

to be completed

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New Generation of mid-IR sources

New Generation of mid-IR sources

One of the main challenges of this research activity is to study and to develop IR fibre lasers emitting beyond 3 µm. Two ways are investigated: luminescence of rare earth and supercontinuum generation. A Supercontinuum generation consists in a spectral broadening of a light pulse by using strong nonlinear effects. It can be noted that currently the commercial IR spectrometers use classical black body sources which are not coherent as regards light or powerful light. With the developed fibre laser, we can expect a light power 100 to 1000 as high as the light emission of a black body. In the case of a fibre laser, all of the light is concentrated in the core of the fibre that can be smaller than 10 µm diameter which enables to obtain a light/surface ratio never observed in the mid-IR.

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Mid-IR spectroscopy

The main infrared signatures of molecular compounds are included in the transparency windows of the chalcogenide fibers and waveguides. Thus, optical fibres or waveguides can be practical sensing tools. Indeed, they transport light to and from the sensing region. In such configurations, the interaction between the light and the environment occurs at the surface of the fibre. The vibrational spectrum which is collected at the output of the fibre constitutes an IR signature very specific of the chemical or biological species. They are consequently good candidates to be used in biological/chemical sensing. In this respect, in the past decade, chalcogenide glass fibres and waveguides have been successfully implemented in Mid-IR spectroscopy experiments, for the detection of bio-chemical species in various fields of applications including water pollution, microbiology and medicine and CO2 detection.

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