CONtinuum à Fibres Infrarouges hAutement Non linéaires – CONFIAN

The purpose of the project called CONFIAN (SuperCONtinuum using highly Non linear infrAred FIbers) is to study and realize a compact broadband optical source emitting in the infrared between 1.5 µm and 5 µm, thanks to highly non linear non silica fibres. This spectral window includes the atmospheric transparency band (3-5 µm) in which numerous chemical species absorb. Thus a supercontinuum type source would find spectroscopic applications for the measurement of atmospheric pollutants, in a configuration close to a Lidar one, presenting a low sensitivity to interferences between chemical species. The first optical supercontinuums that have been reached in silica fibres were corresponding to an anomalous dispersion regime of propagation. But silica has intrinsically a low non linearity, and its infrared transparency is limited around 2 µm in a fibre configuration. Other vitreous materials have thus been studied by the scientific community, especially among those presenting high intrinsic non linearities and extended infrared transparency. However, actually no waveguide of such type is commercially available and a lot of work remains to reach efficient non silica non linear sources. We propose in our project to study the realization of highly non linear infrared optical fibres able to generate a supercontinuum, with the ambitious goal to reach compact fibered optical sources emitting on a wide range in the middle infrared, above 2 µm and until 5-6 µm. Two complementary glass families will be explored, heavy oxide glasses and chalcogenide glasses. These glasses are more transparent in the infrared than silica, until 5 to 10 µm depending on their chemical composition. They are also more non linear, one to three order of magnitude above the non linearity of silica, depending again on their composition. The waveguides which will be elaborated are of two kinds: microstructured fibres and micro-fibres (tapered fibres). A key point will be the control of the zero dispersion wavelength, which must be slightly above the pumping wavelength. For the fibre lasers we plan to use for pumping, this implies to shift this zero dispersion wavelength slightly above 2 µm. The optical properties of the elaborated fibres will be measured, and especially the spectral attenuation, transparency range, non linearity and chromatic dispersion. The conditions required for the generation of a supercontinuum in the mid infrared will be established by modelling. The spectral range and the output power of the supercontinuum will be characterized both numerically and experimentally. To reach our goals, our consortium is composed by 5 teams of complementary expertise: EVC, Perfos, Onera, ICB and Institut Fresnel (IF). Each of them has already a great experience in the field of non linear glasses and optical fibres, and the project fits well with their main research directions. EVC is an expert in the field of infrared glasses and fibres. The technologic platform Perfos has a great experience in the realization of chalcogenide glass performs and microstructured fibres. The ICB is acquiring a specialization in heavy oxide glasses and has an international know how in the field of non linear effects in optical fibres. The IF is well known for its capability in the modelization of microstructured fibres, and after the development of an expertise in the linear effects, it is now studying non linear properties of these new waveguides, and especially supercontinuum generation. The Onera has a great know how in the development of fibered laser sources and OPO (optical parametric oscillators) in the atmospheric II band. It has specifically realized an original fibered source at 1.5 µm with a high spectral brightness, at the best international level.