Laserprobe measurements of SAWs at 3 GHz on a free surface of rotated Y-cut quartz

High frequency SAW filters with narrow transition bands have a wide range of applications since frequency mixing to a lower frequency range (for the purpose of signal processing) may be omitted. The design of these filters requires detailed knowledge about SAW propagation properties, which can be achieved by measuring SAWs in this high frequency range. We have constructed a phase sensitive laserprobe (operating up to 4 GHz) based on the principle of Engan´s laserprobe. The smallest magnitude of SAWs, which can be measured with this new laserprobe, has been demonstrated to be limited by the shot noise generated by the detected light on the photodetectors. Due to this excellent sensitivity, SAWs in the GHz range can be measured both on a free and metalized surface. Laserprobe measurements at about 3 GHz on a free quartz surface are compared with simulations