Modified Mach-Zender laser interferometer for probing bulk acoustic waves

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. (C) 2001 American Institute of Physics.