An all-optical thin-film high-frequency ultrasound transducer

In this work we have created an all-optical ultrasound transducer by integrating an optically-absorbing polyimide thin-film into an etalon sensor. The optically-generated acoustic pulse had an amplitude of 4.3 MPa and a -3 dB bandwidth of 29 MHz centered at 27 MHz. The etalon sensor achieved a Noise-equivalent Pressure of 1.3 Pa / √Hz. When used in pulse-echo mode, the -6 dB upper cutoff frequency of the device's transmit/receive response reached 47 MHz. A 1-D synthetic aperture was created, and imaging results indicate an upper limit of 100 μm and 40 μm on the lateral and axial resolution, respectively. After the incorporation of fiber optics and 2-D beam scanning, potential applications will include endoscopic and intravascular ultrasound.