A high frequency ultrasound array element using thermoelastic expansion in PDMS

The thermoelastic effect was used to produce high frequency, broadband ultrasound in water. A pulsed diode laser, followed by an erbium doped fiber amplifier, was focused onto a light absorbing film deposited on a glass substrate. Conversion efficiency was improved by 18 dB using a polydimethylsiloxane (PDMS) film instead of a more commonly used metallic one. Radiation pattern measurements show that considerable energy is radiated at +/-45 degrees for frequencies beyond 75 MHz. These results show that the thermoelastic effect can be used to produce phased arrays for high frequency ultrasound imaging.