High frequency optoacoustic arrays using etalon detection

Two-dimensional phased arrays for high frequency (>30 MHz) ultrasonic imagi ng are difficult to construct using conventional piezoelectric technology. A promising alternative involves optical detection of ultrasound, where the array element size is defined by the focal spot of a laser beam. Element s ize and spacing on the order of a few microns are easily achieved, suitable for imaging at frequencies exceeding 100 MHz. We have previously shown ima ges made from a receive-only, two-dimensional optoacoustic array operating at 10 to 50 MHz. The main drawback of optical detection has been poor sensi tivity when compared with piezoelectric detection. In this paper, we explor e a different form of optical detection demonstrating improved sensitivity and offering a potentially simple method for constructing two-dimensional a rrays. Results from a simple experiment using an etalon sensor confirm that the sensitivity of etalon detection is comparable with piezoelectric detec tion. This paper concludes with a proposal for a high frequency optoacousti c array system using an etalon.