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

Contact : Johann Trolès

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.

Infrared ceramics

Contact : Odile Merdrignac

Transparent polycrystalline ceramics are an emerging class of optical materials that can reproduce the optical properties of single crystals and glasses while offering enhanced thermomechanical properties. The development of ceramics transparent in the infrared is of great interest to the civil and military sectors, for example, for thermal imaging and the manufacture of missile domes. Zinc sulfide (ZnS), the dome material currently in use, is produced by CVD and HIP techniques as coarse-grained ceramics with low hardness which do not satisfactorily meet the erosion resistance requirement. The Glass and Ceramics group has developed a sintering process using nanopowders (patented) to produce transparent ZnS ceramics of comparable optical quality and twice the hardness of commercial products. The innovative process also makes it possible to significantly reduce the cost of optics, suggesting a democratization of applications, particularly for the civilian field.

The expertise acquired in the manufacture of ZnS optics has led to real advances in the ability to create new materials that are transparent in the infrared. Cubic ternary sulfides, like calcium lanthanum sulfide (CaLa2S4), are currently under investigation in the framework of ANR project and PhD studies.

Main collaborations: DGA, Solcera Advanced Materials (Evreux)

We have also shown the very high efficiency of ZnS and CaLa2S4 powders as host matrices, respectively, of transition metal and rare earths ions, for the emission in the mid-infrared and the conversion of frequency. By capitalizing on the expertise acquired in the manufacture of transparent ceramics, we can expect the generation of new light sources in the mid-IR (3-5μm) and new solid-state laser gain media.

Thin film and waveguides

 
In the many fields where integrated optics can potentially be used, the development of amplifiers and laser sources, optical sensors, and all-optical devices based on non-linear properties will make it possible to provide low-cost and highly compact optical systems. Chalcogenide glasses offer advantages such as a wide transmission window and high linear and non-linear refractive index, making integrated optics suitable for the sensitive detection of biological or environmental variations. Different methods of PVD such as evaporation, pulsed laser deposition, and RF sputtering can produce chalcogenide thin films. The first step is to produce chalcogenide slab waveguides, i.e. guiding structures composed of a thin high-index layer deposited on a low-index substrate or buffer layer. Our slab waveguides based on amorphous chalcogenide films of various composition including (Ge, As, Sb, Ga, In, S, Se, Te) with good adhesion and controlled composition can also include rare earth ions for light emissions. Patterning techniques from microelectronics enable to design and manufacture complex optical devices on a compact chip in order to develop an optical integrated platform for various photonics applications like bio-chemical sensors, NIR and MIR sources, non-linear devices.
Main collaboration: Institute of FOTON, University of Pardubice, BRGM, IFREMER, CIMAP, IMN, IMMM, University of Mons.

 

All the field of thin film in the lab
ONL properties and plasmonic

New Generation of mid-IR sources

Contact : Virginie Nazabal, Johan Trolès

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.

Source MIR

Mid-IR spectroscopy

Contact : Virginie Nazabal, Johan Trolès

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.

sensors

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