Thermoelastic generation of ultrasound using an erbium doped fiber amplifier

Two-dimensional phased arrays for high frequency (>30 MHz) ultrasonic imaging are difficult to construct using piezoelectric technology. A promising alternative involves optical generation of ultrasound, where an array element is defined by the size and location of a laser beam. The thermoelastic effect can be used to generate broadband ultrasound by optical absorption of an amplitude modulated laser pulse. The authors have built a fiber based optical amplifier to amplify pulses from a modulated diode laser to peak powers sufficient to generate ultrasound detectable with conventional transducers. These results demonstrate the potential of the fiber amplifier approach for high frequency optoacoustic arrays.