Laser-induced thermal acoustics (LITA) signals from finite beams.

摘要: Laser-induced thermal acoustics (LITA) is a four-wave mixing technique that may be employed to measure sound speeds, transport properties, velocities, and susceptibilities of fluids. It particularly effective in high-pressure gases (>1 bar). An analytical expression for LITA signals derived by the use linearized equations hydrodynamics light scattering. This analysis, which includes full finite-beam-size effects optoacoustic thermalization electrostriction, predicts amplitude time history narrow-band time-resolved broadband spectrally resolved (mulitplex) signals. The behavior detected signal depends significantly on detection solid angle, with implications measurement diffusivities proper physical picture other elements physics emerge from analysis are discussed. Theoretical compared experimental data.