Piezoelectric Multimaterial Fibers
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Piezoelectric Multimaterial Fibers Noémie Chocat1, Zheng Wang2,3, Shunji Egusa2, Zachary M. Ruff1, Alexander M. Stolyarov 4, Dana Shemuly1, Fabien Sorin1,2, Peter T. Rakich2, John D. Joannopoulos2,3 and Yoel Fink1,2 1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, U.S.A. 2 Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, U.S.A. 3 Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, U.S.A. 4 School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, U.S.A. ABSTRACT Here we report on the design, fabrication, and characterization of fiber containing an internal crystalline non-centrosymmetric phase enabling piezoelectric functionality over extended fiber lengths [1]. A ferroelectric polymer layer of 30 m thickness is spatially confined and electrically contacted by internal viscous electrodes and encapsulated in an insulating polymer cladding hundreds of microns in diameter. The structure is thermally drawn in its entirety from a macroscopic preform, yielding tens of meters of piezoelectric fiber. Electric fields in excess of 50V/m are applied through the internal electrodes to the ferroelectric layer leading to effective poling of the structure. To unequivocally establish that the internal copolymer layer is macroscopically poled we adopt a two-step approach. First, we show that the internal piezoelectric modulation indeed translates to a motion of the fiber’s surface using a heterodyne optical vibrometer at kHz frequencies. Second, we proceed to an acoustic wave measurement at MHz frequencies: a water-immersion ultrasonic transducer is coupled to a fiber sample across a water tank, and frequency-domain characterizations are carried out using the fiber successively as an acoustic sensor and actuator. These measurements establish the broadband piezoelectric response and acoustic transduction capability of the fiber. The potential to modulate sophisticated optical devices is illustrated by constructing a single-fiber electricallydriven device containing a high-quality-factor Fabry-Perot optical resonator and a piezoelectric transducer. INTRODUCTION In recent years, a unique process has emerged that allows a multiplicity of solid materials with disparate electrical, optical, and mechanical properties to be arranged into a single fiber material. Multimaterial fibers have extended the responsivity and functionality of fibers from the traditional optical transmission domain to encompass optoelectronic properties. Applications such as fiber reflectors, thermal detectors, photodetectors, surface-emitting fiber lasers, and fiber diodes have recently been realized using this process [2]. However, multimaterial fibers similar to their traditional single-material fiber counterparts have been static devices, incapable of controllably changing their properties over a wide rang
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