A new kind of ultrasonic transducer for medical imaging by combining electromechanical and optical properties of PZN-PT single crystal

Summary form only given. For medical imaging and other applications, the widely used devices are based on ultrasonic pulse-echo image formation, that is, generating and receiving ultrasound using piezoelectric effect. Recently, an optical detection of high frequency ultrasonic signal based on interferometer has been developed by several groups. This new approach has many advantages, such as broad frequency band, easy construction for 2D arrays. For a typical interferometer, linear operation has to be achieved by stabilizing at quadrature position. Several methods can be used for tuning, such as a controlled loop to shift the laser frequency, changing the interferometer length or tilting the incident laser beam. However, due to the presence of low-frequency dynamic strains in a real situation, it is almost impossible to tune the each element instantly for a 2D array with large number elements. The other limitation is rather obvious that all these devices are passive sensors - they have to work with another ultrasonic transducer to generate the acoustic pulse. In order to overcome these disadvantages, a new design is proposed in which only one element is shown. Here, a thin active material layer serves as both transmitter and receiver of ultrasound. The thin layer forms an intrinsic interferometer by a fully reflective mirror/electrode on one side and a partially reflective mirror/electrode on the other side. Since the finesse is very low, the optical cavity can be treated as Mach-Zehnder interferometer. Such interferometric structure can convert the ultrasound vibration to the output light intensity change as an ultrasonic sensor.