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The inverse Cotton-Mouton effect observed for the first time

A Magneto Optics effect observed for the first time at LNCMI: towards a new photonics device?

Magneto optics is an old field of research, as old as 1845 when Faraday discovered that a magnetic field can change light polarization, but it is still a surprising one.

Physicists at the LNCMI-T have observed for the first time that when a light beam passes through a medium in the presence of a transverse magnetic field, the medium becomes magnetized. This magnetization obtained is proportional to the laser power and to the value of the external magnetic field. This effect corresponds to a non resonant excitation of the medium constituents that changes its microscopic properties. Its existence has been predicted since the beginning of non-linear optics in the sixties but it has been somewhat forget in textbooks. It is generally known as the Inverse Cotton-Mouton effect.

Physicists have observed this magnetization in a crystal of common use in optics, a Terbium Gallium Garnet (TGG). The experiment is based on the use of a pulsed powerful laser, a magnetic field and an electronic circuit to detect the induced magnetization that is typically one million times smaller than the external magnetic field for this kind of crystal. Thanks to it an electric signal is obtained indicating that the crystal has been illuminated by the laser.

Though the first motivation of physicists is to study more fundamental aspects of this phenomenon [1], it is clear that the whole system constitutes a device that may have industrial applications in the field of photonics. A patent is now pending under CNRS sponsorship. This shows once more how fundamental researches are also fundamental to the industrial development. This observation will be published on a journal of the European Physical Society [2], but physicists are already working to arrive to an industrial prototype of the device which could be commercialized.

[1] Inverse Cotton-Mouton effect of the vacuum and of atomic systems, C. Rizzo, A. Dupays, R. Battesti, M. Fouché and G. L. J. A. Rikken, EPL 90, 64003 (2010) ;

[2] Observation of the Inverse Cotton-Mouton Effect, A. Ben-Amar Baranga, R. Battesti, M. Fouché, C. Rizzo, and G. L.J.A. Rikken, arXiv:1009.3152, in press EPL.

Contact : Rémy Battesti

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