Phase-sensitive absolute-amplitude measurements of surface waves using heterodyne interferometry

Phase-sensitive absolute-amplitude measurements of surface waves using heterodyne interferometry. We describe a novel heterodyne interferometer for scanning surface-acoustic waves at high frequencies, up to 6 GHz. The heterodyne operation facilitates the measurement of the absolute amplitude of the surface waves without calibration. It simultaneously also enables measuring the phase. The amplitude and phase information allows a precise characterization of the surface acoustic waves. Moreover, the wave motion can be visualized in the form of animations to gain insight. The interferometer has been tested by measuring a 167 MHz SPUDT device and a 374 MHz fan-shaped SAW filter.