ניתוח גלי אור וקול מולכים בהתקני סיבים אופטיים בעלי קוטר קטן

Modeling of guided acoustic and optical modes in tapered fiber devices

Optical fibers came about as means to guide light. Much less attention is given to the fact that fibers also support guided ultrasound waves. Guided light and sound waves can interact with each other. One may use light to stimulate guided sound waves in the fiber, and in turn use the same sound waves to scatter guided light. Unlike the optical mode, which is strictly confined by design to an inner core, the acoustic waves extend across the entire fiber transverse profile and reach its outer boundary. This property has several interesting implications. Over the last two years, our group has shown that guided acoustic waves can be used to analyze liquids outside the cladding of standard optical fibers, even when guided light never comes into contact with the substance under test. This concept works around a limitation which held back optical fiber sensors for forty years.

Work thus far has been restricted to standard fibers only. The fibers, however, may be tapered down to diameters on the order of 1 micron. Tapered fibers bring two potential benefits to the study of guided light and sound waves: 1) their confinement of light and sound in narrow cross-sections with large overlap increases the interaction strengths; and 2) both guided light and guided sound may come in contact with surrounding media. These properties are now being studied by our group. They may lead to new sensor concepts and applications.

The objective of the project is to put together a comprehensive analytical model for guided acoustic waves in tapered fibers, and for their interaction with guided light. The elastic wave equation will be studied from first principles, using extensive literature. Numerical simulations will be carried out over matlab code, and also using commercial finite element software. Results will serve to guide ongoing experiments, and will be compared against measured data.

Milestones and formal requirements include:

• A written mid-term report (to be submitted March 2018, in English)
• Mid-term presentation in the Zadok group meeting (to be given March 2018, in Hebrew)
• A final report (to be submitted no later than September 2018, in English)
• An oral defense and presentation of the project, in front of an examination committee consisted of the project advisors and external experts (to be given in Hebrew, no later than October 2018).

דרישות:

Electro-optics track (mandatory); Elective class "Advanced Topics in Optical Communications" (83648), to be taken during spring term 2018 (mandatory).

מקורות:

Y. Antman, A. Clain, Y. London, and A. Zadok, "Optomechanical sensing of liquids outside standard fibers using forward stimulated Brillouin scattering," Optica 3, 510-516 (2016).
http://www.eng.biu.ac.il/zadoka/files/2011/06/optica-3-5-510.pdf

H. H. Diamandi*, Y. London*, and A. Zadok, "Opto-mechanical inter-core cross-talk in multi-core fibers," Optica 4, 289-297 (2017).
http://www.eng.biu.ac.il/zadoka/files/2017/02/optica-4-3-289.pdf