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Nature Communications

Nature Communications FEMTO-ST/Optique - Laboratoire Charles Fabry- Labex ACTION

A new type of Brillouin radiation observed in subwavelength optical fibre

 

Scientists at the CNRS FEMTO-ST Institute in Besançon, France, and at the Institut d’Optique, in Paris, have recently discovered a new type of Brillouin light scattering driven by surface acoustic waves in a subwavelength optical fibre.

These hair-like slivers of silica glass, fabricated by tapering optical fibres, enable enhanced nonlinear optical effects and applications not currently possible with comparatively bulky optical fibres. Among nonlinear phenomena, Brillouin scattering is a fundamental interaction between light and sound with important implications ranging from optical sensors to slow and fast light. In standard optical fibres, light both excites and feels shear and longitudinal bulk elastic waves, giving rise to forward guided acoustic wave Brillouin scattering and backward stimulated Brillouin scattering.

In a subwavelength-diameter optical fibre, the situation changes dramatically, as Beugnot et al. recently reported In Nature Communications, with the first experimental observation of Brillouin light scattering from surface acoustic waves. Exploring this novel effect, researchers at FEMTO-ST have observed that light can shake and distort the optical microwire through electrostriction, leading to mechanical undulations of a few nanometers. More specifically, they have shown that these surface acoustic waves travel at a specific velocity of 3400 meter per seconde and backscatter the light with a Doppler shift of about 6 GHz.

"We had never before been able to observe this type of surface Brillouin scattering as the dimensions of optical fibres must be smaller than the wavelength of the light, which is 50 times smaller than a human hair ! ", said Thibaut Sylvestre, a CNRS researcher at the FEMTO-ST Institute.

As these acoustic resonances are highly sensitive to surface defects or features, surface acoustic wave Brillouin scattering opens new opportunities for various sensing and detection applications, but also in other domains such as microwave photonics and nonlinear plasmonics. From a more fundamental viewpoint, their discovery contributes to the further understanding of the intriguing light-sound interactions in tiny photonic devices.

Contacts : Thibaut Sylvestre or Jean-charles Beugnot, CNRS Researchers, Institut FEMTO-ST, Université de Franche-comté, Besançon.

Article Info:

Jean-Charles Beugnot, Sylvie Lebrun, Gilles Pauliat, Hervé Maillotte, Vincent Laude, and Thibaut Sylvestre, "Brillouin light scattering from surface acoustic waves in a subwavelength-diameter optical fibre"


 

This work was supported by the Labex ACTION program (contract No. ANR-11-LABX-0001-01).

http://www.nature.com/ncomms/2014/141024/ncomms6242/full/ncomms6242.html

faisceau laser

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faisceau rouge

Figure 2: Picture of a silica microwire illuminated by a red He:Ne laser.

 (© T. Sylvestre - FEMTO-ST)

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