INVESTIGATION OF SPURIOUS MODE IN PIEZOELECTRIC CERAMIC RESONATORS USING OPTICAL-FIBER INTERFEROMETRIC SENSING

It is possible to precisely measure the vibration amplitudes of up to angstrom order using the optical fiber interferometric sensing system by Yasuo Hirose of Yokohama National University. Vibration amplitude m easurements were made across the electrode's surface of the resonators in a certain frequency range. Noticeable spurious mode occurs close t o the anti-resonance frequency of the third thickness extensional mode (TE3) of the PbTiO3 based piezoelectric ceramic resonators. This meas urement method revealed that, at the spurious mode, the contour of amp litudes across the electrode is in the shape of the twin peaks. Locati on of the single peak contour, just before and after the spurious mode , was respective to that of the twin spurious peaks. It is believed th at the dislocation of the amplitude contour from the center of the cir cular electrode was due to the taper in thickness of the resonator chi ps.