A research system of underwater acoustic waves based on interferometry is proposed for the study of laser-induced underwater acoustic waves. Neodymium:Yttrium Aluminum Garnet (ND:YAG) laser is adapted to interact with the water surface to produce acoustic waves in this system. The beam emitted from the He-Ne laser is divided into two parts: reference beam and probe beam, and the probe beam goes through the stimulated water tank, interfered with the reference beam. The characteristics of laser-induced underwater acoustic waves are determined by observing the change rate of interference fringes, thus realizing the study of laser-induced underwater acoustic wave's detection. In the experiments, by comparing influences on the change rate of interference fringes induced by laser monopulse energy, the rate of water absorption of laser energy and laser pulse energy density as well as other parameters, a conclusion can be made that the laser monopulse energy plays the prior role, and the rate of water absorption of laser energy is posterior. The feasibility of the method using laser interferometry to detect laser-induced underwater acoustic waves in experiments is verified, providing theoretical guidance for the research and practical application of laser-induced acoustic waves. The results show that the system is stable and easy to operate.

Study of laser induced acoustic waves in water based on interferometry

Acoustic waves in water may be produced by the absorption of infrared energy from a pulsed laser. The temperature distribution in water for a kilowatt pulse with a duration of the order of a millisecond can be described in terms of the beam parameters and the optical absorption coefficient of water. The expression for the temperature distribution has been solved numerically. The acoustic waves were studied by the use of hydrophones in an anechoic tank filled with tap water. Cylindrical waves with exponentially decreasing amplitudes with depth were produced by the absorption of laser radiation. The velocity of these waves was in close agreement with the velocity of acoustic waves in water.

http://iopscience.iop.org/article/10.1088/0022-3727/7/14/317/pdf

Aijaz Karim

Papers

Laser-induced acoustic waves in water