A new theoretical approach to photoacoustic signal generation

TLDR

Photoacoustic signal generation in aqueous media is dominated by local thermal expansion, also known as thermoelastic PA. The study introduces a new physical explanation of the spherical PA profile that enables prediction of signals from other geometries and temporal shapes. The authors analyze characteristic PA signal profiles for fundamental and practical source geometries, including attenuation and deformation from viscous and thermoelastic losses. They derive an analytic transient for a spherical Gaussian spatiotemporal source and present experimental PA signals for various geometries and diameters.

Abstract

From the various mechanisms of photoacoustic (PA) signal generation, the one due to local thermal expansion in aqueous media is treated here in detail. This mechanism is also referred to as thermoelastic PA signal generation. A new physical explanation of the spherical PA profile is presented, from which the signals generated by other source geometries and temporal profiles can be deduced. The characteristic PA signal profiles are discussed for some fundamental and practical source geometries. Also the PA signal attenuation and deformation due to viscous and thermoelastic losses is discussed. The analytic result for the transient generated by a spherical Gaussian spatiotemporal PA source is presented. Experimental PA signals are shown for several geometries and source diameters.