When aqueous suspensions of gold nanorods are irradiated with a pulsing laser (808 nm), pressure waves appear even at low frequencies (pulse repetition rate of 25 kHz). We found that the pressure wave amplitude depends on the dynamics of the phenomenon. For fixed concentration and average laser current intensity, the amplitude of the pressure waves shows a trend of increasing with the pulse slope and the pulse maximum amplitude. We postulate that the detected ultrasonic pressure waves are a sort of shock waves that would be generated at the beginning of each pulse, because the pressure wave amplitude would be the result of the positive interference of all the individual shock waves.
© 2013 Optical Society of America
Original Manuscript: February 22, 2013
Revised Manuscript: May 17, 2013
Manuscript Accepted: June 1, 2013
Published: June 27, 2013
Cristina Sánchez López de Pablo, Julio Alberto Ramos Ávila, Tamara Fernández Cabada, Francisco del Pozo Guerrero, and José Javier Serrano Olmedo, "Photoacoustic effect measurement in aqueous suspensions of gold nanorods caused by low-frequency and low-power near-infrared pulsing laser irradiation," Appl. Opt. 52, 4698-4705 (2013)