Generating underwater acoustic signals from a remote, aerial location by use of a high-energy pulsed infrared laser has been demonstrated. The laser beam is directed from the air and focused onto the water surface, where the optical energy was converted into a propagating acoustic wave. Sound pressure levels of 185 dB re μPa (decibel re μPa) were consistently recorded under freshwater laboratory conditions at laser-pulse repetition rates of up to 1000 pulses/s. The nonlinear optoacoustic transmission concept is outlined, and the experimental results from investigation of the time-domain and frequency-domain characteristics of the generated underwater sound are provided. A high repetition rate, high-energy per pulse laser was used in this test under freshwater laboratory conditions. A means of deterministically controlling the spectrum of the underwater acoustic signal was investigated and demonstrated by varying the laser-pulse repetition rate.
© 2005 Optical Society of America
Original Manuscript: February 17, 2004
Revised Manuscript: September 28, 2004
Manuscript Accepted: September 29, 2004
Published: January 1, 2005
Fletcher Blackmon and Lynn Antonelli, "Experimental demonstration of multiple pulse nonlinear optoacoustic signal generation and control," Appl. Opt. 44, 103-112 (2005)