A scanning homodyne Michelson interferometer is constructed for two-dimensional imaging of high-frequency surface acoustic wave (SAW) fields in SAW devices. The interferometer possesses a sensitivity of ~10(-5)nm/ radicalHz , and it is capable of directly measuring SAW's with frequencies ranging from 0.5 MHz up to 1 GHz. The fast scheme used for locating the optimum operation point of the interferometer facilitates high measuring speeds, up to 50,000 points/h. The measured field image has a lateral resolution of better than 1 mu;m . The fully optical noninvasive scanning system can be applied to SAW device development and research, providing information on acoustic wave distribution that cannot be obtained by merely electrical measurements.

This letter reports the usage of a modified Mach–Zehnder interferometer for visualization of the mechanical vibrations of high-frequency, bulk-mode, thin-film resonators. The setup is capable of detecting frequencies from 30 kHz up to 12 GHz with an amplitude down to less than 10 pm, which means a dynamic range above 80 dB. The achieved lateral resolution of the measured field image is more than 300 nm. Due to a new phase stabilizing system phase sensitive measurements are possible, additionally bringing up the possibility of establishing a tremendous measurement speed of up to 5 million points/h. This setup can be applied to bulk acoustic wave development in order to provide information such as material parameters, to verify theoretical models and to learn about device behavior which cannot be done using only electrical measurement tools.

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We discuss an acoustic loss mechanism in surface-acoustic wave resonators on 36° YX-cut lithium tantalate substrate. Recent acoustic field scans performed with an optical Michelson interferometer reveal a spatially asymmetric acoustic field atop the busbars of a resonator, giving rise to acoustic beams which escape the resonator area and lead to undesired losses. Here, we link the phenomenon with the inherent crystalline anisotropy of the substrate: the shape of the slowness curves and the asymmetry of the polarization for leaky surface-acoustic waves, propagating at an angle with respect to the crystal X-axis.

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