Phase-sensitive and fast-scanning laser probe system for radio frequency surface/bulk acoustic wave devices

This paper reviews a phase-sensitive and fast-scanning laser probe system developed by the authors´ group for the diagnosis of radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) devices. The system is based on the Sagnac interferometer, which is insensitive to low frequency vibration. This feature allows us to maximize the scanning speed without sacrificing the signal-to-noise ratio of the measurement. It is demonstrated that high quality two-dimensional (2D) image of SAW/BAW field patterns can be captured in minutes order. Currently the maximum applicable frequency is 6 GHz. Because of the phase sensitivity, the measured field in the space domain is readily converted into the wavenumber domain by the 2D Fourier Transform.