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Mid-Infrared methane (CH4) spectroscopy results were obtained in band III beyond 7 µm. To achieve this, the generation of supercontinuum covering the spectral range between 5 and 12 µm was realized by using purified chalcogenide optical fibers free of highly toxic elements such as arsenic and antimony. Besides a pumping with an optical parametric amplifier, an all fibered pumping scheme has also been investigated. In both configuration, supercontinuum absorption spectroscopy experiments have allowed for CH4 sensing, concentration as low as 14 ppm has been detected.

We propose and demonstrate the concept of beam-by-beam cleaning in multimode optical fibres, i.e., the increase of the spatial quality of an intense laser beam, induced by a relatively weak, quasi singlemode seed beam. This effect, which relies on the Kerr nonlinearity of the fibre, is quite efficient: a seed beam is capable of providing a bell-shape to a ten times more powerful beam. Our results pave the way for the development of a new class of all-optical switching devices for intense laser beams.