"Opto-mechanics in fibers and silicon-photonic circuits"

Avi Zadok, Professor, Faculty of Engineering and Institute for Nano-Technology and Advanced Materials, Bar-Ilan University, Israel

February 5th (Tuesday), 1:30pm
Engineering Sciences Building (ESB), Room 2001

The interactions between light and sound waves draw the attention of researchers since the 1880’s. Light waves in bulk media may stimulate mechanical (acoustic) oscillations through electrostriction. The sound waves, in turn, can modulate and scatter light due to photo-elasticity. In this talk, I present several recent demonstrations of opto-mechanical interactions in optical fibers and silicon photonics, and their applications towards sensing and all-optical signal processing.

Optical fiber sensors face a long-standing dilemma: light is confined to the fiber’s inner core, whereas the substance under test lies outside the boundary of the cladding, or even the protective coating. The optical stimulation of guided acoustic modes works around this difficulty. In the first part, I present opto-mechanical time-domain reflectometry measurements that map the properties of liquids outside the fiber, where light cannot reach. The measurement range is 3 km, and the spatial resolution is 50 meters. The protocol is applicable to commercially-available coater fibers. The interplay between the Kerr effect and opto-mechanics in the nonlinear propagation of multiple wave components is addressed as well.

In the second part, the concept is extended to multi-core fibers. The opto-mechanics of these fibers gives rise to inter-core cross-phase modulation, even when the constituent cores are completely isolated from an optical standpoint. Such crosstalk can be driven into stimulated oscillations of highly-coherent phonon modes. Lastly, surface acoustic waves at GHz frequencies are introduced to photonic integrated circuits in standard silicon-on-insulator. The acoustic waves are stimulated by absorption of pump light in metallic grating patterns. Acousto-optic modulation of probe light in ring resonators is demonstrated. The devices function as integrated microwave-photonic filters with free spectral ranges of tens of MHz.

[1] H. H. Diamandi, Y. London, and A. Zadok, “Opto-mechanical inter-core cross-talk in multi-core fibers,” Optica 4, 289-297 (2017).
[2] G. Bashan, H. H. Diamandi, Y. London, E. Preter, and A. Zadok, “Optomechanical time-domain reflectometry,” Nature Communications 9, 2991 (2018)
[3] Y. London, H. H. Diamandi, G. Bahsan, and A. Zadok, “Invited Article: Distributed analysis of nonlinear wave mixing in fiber due to forward Brillouin scattering and Kerr effects,” Applied Physics Letters – Photonics 3, 110804 (2018).

About Avi Zadok:

photo of Avi ZadokDr. Avi Zadok received his Ph.D. in Electrical Engineering from Tel-Aviv University in 2008. Between 2007 and 2009 he was a post-doctoral research fellow at the Department of Applied Physics, Caltech. Since 2009 he is with the Faculty of Engineering of Bar-Ilan University, Israel, where he is Full Professor since 2017. His research group works on nonlinear and opto-mechanical propagation effects in optical fibers, with emphasis on sensing applications, and on integrated photonic devices in silicon and glass substrates. Dr. Zadok received the Krill Award of the Wolf Foundation in 2013. He was elected to the Israel Young Academy of Science in 2016, and currently serves in its Steering Committee.

Hosted by: Professor Dan Blumenthal, ECE and TOEC Seminar