Phase-sensitive and fast-scanning laser probe system for diagnosis of high frequency acoustic wave devices

Abstract

This paper describes a phase-sensitive and fast-scanning laser probe developed by the authors’ group for the diagnosis of acoustic wave devices used as a platform of highly sensitive sensors. Surface vibration is detected by the Sagnac interferometer, which is insensitive to low frequency vibration. From this feature, we can maximize the scanning speed without influence of low frequency vibration and sacrificing the signal-to-noise ratio of the measurement. It is demonstrated that high quality twodimensional (2D) image of acoustic wave field patterns can be captured in minutes order. Currently the maximum applicable frequency is 2.5 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. It is also demonstrated how effective the wavenumber domain analysis is for the purpose.