Heterodyne laser-Doppler interferometric characterization of contour-mode resonators above 1 GHz

This paper reports the design and optical characterization of PZT transduced high-overtone width-extensional mode resonators with resonance frequency above 1 GHz. For the first time, a novel technique to measure resonance frequencies and vibrations of contour-mode resonators optically up to 1.2 GHz using only a 618 MHz carrier frequency is demonstrated. The output signal from the photo detector of the vibrometer is digitized by a fast digital oscilloscope and demodulated off-line in a computer. A signal processing algorithm has been developed to acquire frequency components from the photo detector which are higher than the carrier frequency to construct I and Q (in-phase and quadrature) signals from a virtual carrier signal with frequency 2× of the original carrier frequency. This method enabled us to realize an algorithm to extend the measurement bandwidth by a factor of 2 for small vibration amplitudes (< 20 nm).