Optical polarimetric measurement of surface acoustic waves.

Surface acoustic wave (SAW) is utilized in diverse fields ranging from physics, engineering, to biology, for transducing, sensing and processing various signals. Optical measurement of SAW provides valuable information since the amplitude and the phase of the displacement field can be measured locally with the resolution limited by the spot size of the optical beam. So far, optical measurement techniques rely on modulation of optical path, phase, or diffraction associated with SAW. Here, we demonstrate that SAW can be measured with an optical polarimeter. We show that the slope of the periodically tilting surface due to the coherently driven SAW is translated into the angle of polarization rotation, which can be straightforwardly calibrated when polarimeters work in the shot-noise-limited regime. The polarimetric measurement of SAW is thus beneficial for quantitative studies of SAW-based technologies.