Photoacoustic signal formation in absorbing and scattering liquids

The so-called photoacoustic technique combines optical properties, such as absorption and scattering, with acoustic properties, such as sound velocity and absorption, to monitor and measure the physical properties of materials. This paper comprises a theoretical study on the properties of acoustic pulses and a discussion on earlier theories presented in literature. It also describes and analyzes the results of simulation tests based on the Monte-Carlo method, undertaken to examine the effects that absorption and scattering co-efficients of two-layer media have on the shape of the acoustic transmitter. Finally, the theoretical results are corroborated with measurements using a CO2 laser and a two-wavelength diode laser PA system, developed during the study