[Phys-seminars] 2017-05-11 Lasers Seminar

barmash barmash at bgu.ac.il
Fri May 5 19:27:45 IDT 2017

Lasers Seminar

 DATE: 11-05-17

 TIME: 15:30

 PLACE: Physics building (#54) room 207

Opto-mechanics of standard fibers: Sensing, crosstalk and oscillations

Prof. Avi Zadok, Faculty of Engineering and Institute for Nano-Technology, Bar-Ilan University

We all know that optical fibers guide light. Much less attention is drawn to the fact that optical fibers also support guided sound waves. The propagation of light in the fiber may stimulate the oscillations of these acoustic modes. The sound waves, in turn, may scatter light waves and couple power between optical fields. Although the phenomenon is known since the 1980\'s, it has found little role in fiber-optics technology to-date. Guided acoustic modes of optical fibers do give us, however, a property that guided light cannot: the transverse profiles of guided sound waves are not confined to the inner core. Instead, they spread across the entire cladding cross-section, and reach the outer cladding boundary. Our group has been investigating the coupling between light and sound in fibers over the last two years. In this talk, I will present several implications of such coupling, which might appear surprising at first. On top of their fundamental interest, the results are of p
 ractical significance in the contexts of fiber-sensors, telecommunication, and microwave photonics: 1.Acoustic wave scattering allows us to take measurements of substances outside the cladding boundary of a standard unmodified fiber, where light does not reach. We are therefore able to \"listen\" where we cannot \"look\". The mechanical impedance of surrounding media is measured with 1% accuracy. The protocol has been recently extended to distributed analysis. 2.Acoustic wave scattering induces cross-talk among the different cores of multi-core fibers, even when the direct coupling of optical power is entirely negligible. 3.Lastly, guided acoustic waves scattering can lead to opto-electro-mechanic oscillations at radio frequencies in standard fiber.

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