Abstract

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 is particularly effective in high-pressure gases (>1 bar). An analytical expression for LITA signals is derived by the use of linearized equations of hydrodynamics and light scattering. This analysis, which includes full finite-beam-size effects and the optoacoustic effects of thermalization and electrostriction, predicts the amplitude and the time history of narrow-band time-resolved LITA and broadband spectrally resolved (mulitplex) LITA signals. The time behavior of the detected LITA signal depends significantly on the detection solid angle, with implications for the measurement of diffusivities by the use of LITA and the proper physical picture of LITA scattering. This and other elements of the physics of LITA that emerge from the analysis are discussed. Theoretical signals are compared with experimental LITA data.

© 1995 Optical Society of America

Beam misalignments and fluid velocities in laser-induced thermal acoustics

Stefan Schlamp, Eric B. Cummings, and Hans G. Hornung
Appl. Opt. 38(27) 5724-5733 (1999)

Laser-induced thermal acoustics: simple accurate gas measurements

E. B. Cummings
Opt. Lett. 19(17) 1361-1363 (1994)

Laser-induced thermal-acoustic velocimetry with heterodyne detection

Stefan Schlamp, Eric B. Cummings, and Thomas H. Sobota
Opt. Lett. 25(4) 224-226 (2000)

Simultaneous velocimetry and thermometry of air by use of nonresonant heterodyned laser-induced thermal acoustics

Roger C. Hart, R. Jeffrey Balla, and G. C. Herring
Appl. Opt. 40(6) 965-968 (2001)

Accuracy and uncertainty of single-shot, nonresonant laser-induced thermal acoustics

Stefan Schlamp, Hans G. Hornung, Thomas H. Sobota, and Eric B. Cummings
Appl. Opt. 39(30) 5477-5481 (2000)