This paper reviews the theory and applications of photoacoustic (also called optoacoustic) methods belonging to the more general area of photothermal measurement techniques. The theory covers excitation of gaseous or condensed samples with modulated continuous light beams or pulsed light beams. The applications of photoacoustic methods include spectroscopy, monitoring deexcitation processes, probing physical properties of materials, and generating mechanical motions. Several other related photothermal methods, as well as particle-acoustics and wave-acoustics methods are also described. This review complements an earlier and narrower review [Rev. Mod. Phys. 53, 517 (1981)] that is mainly concerned with sensitive detection by pulsed photoacoustic spectroscopy in condensed matter.

Applications of photoacoustic sensing techniques

Photoacoustic and related photothermal techniques

Theory of Photothermal and Photoacoustic Effects in Condensed Matter

Photoacoustic and electroacoustic properties of semiconductors

This paper provides physical discussions of factors controlling sensitivity in photothermal spectroscopy, in particular, photoacoustic spectroscopy and probe-beam deflection spectroscopy. Wc consider the physical basis for signal generation and enhancement methods for pulsed and continuous-modulated excitations as well as the various sources of noises which become significant when the absorption approaches the part-per-million level or below. Proper signal enhancement and noise suppression are essential to make photothermal spectroscopy a sensitive tool.

Signal Enhancement and Noise Suppression Considerations in Photothermal Spectroscopy

The phase angle φ of a gas‐coupled photoacoustic (PA) signal has been measured as a function of coupling gas column thickness lg for a ‘‘one‐dimensional’’ PA cell. The PA signal is excited by a modulated continuous laser beam incident on an opaque solid surface of silicon. We show that the observed data can be explained in a PA model including the consideration of a residual volume in the PA cell, together with the consideration of viscous damping of the PA signal at small lg.

P. Korpiun

Papers

Effect of coupling gas viscosity on the photoacoustic signal