Photoacoustic Generation Using Gold Nanostructure Fabricated by Femtosecond Laser

Ultrasound generation through photoacoustic principle is a promising method for novel ultrasonic applications. This paper describes a photoacoustic generation method using gold nanostructure fabricated by a femtosecond laser. A nanopattern was fabricated on a quartz substrate. A gold film with a thickness of 50 nm was thermally deposited on the nanoparttern to form a gold nanostructure. The quartz substrate with the gold nanostructure was excited by a nanosecond laser to generate acoustic signals via photoacoustic principle. A quartz substrate coated with a 50 nm thickness gold layer was excited in the same condition for the comparison purpose. Experiment results showed that acoustic signals with amplitudes of 1.56 kPa at a distance of 1.5 mm away from the substrate were generated under the laser energy density of 0.27 mJ/cm².