Development of fast-scanning laser probe system based on knife-edge method for diagnosis of rf surface acoustic wave devices

This paper describes the development of a high- speed laser probe system for surface acoustic wave (SAW) devices. A fast scanning rate of 2.5 kS/s is realized by continuous stage translation and successive acquisition of the detector output by a high-speed data-logger. Trigger pulses are generated from the output of a high-precision linear- scale installed in the translation stage and fed to the data- logger for the synchronization with the stage movement. The phase-sensitive knife-edge method is employed for the optical detection. This makes the system very unsusceptible to low-frequency mechanical vibration caused by the fast stage translation. The system is applied for the characterization of spurious resonance modes in SAW devices. In conjunction with skillful use of image processing in wavenumber domain, it is shown how the present system is effective in the diagnosis and development of SAW devices.