A calibration technique for frequency domain photothermoacoustics

Photoacoustic (or more precisely, photothermoacoustic) signals are generated by the absorption of photons, expressed as acoustic waves, and can be related to the incident laser fluence rate. Here a calibration procedure for frequency domain (FD) photoacoustics is presented which utilizes the relationship between photoacoustic (PA) signal amplitude and laser fluence rate. The sample is irradiated with a continuous wave laser which is amplitude modulated at varying frequencies. Applying the calibration procedure to the PA detected signals, a linear relationship is obtained between the fluence rate and the signal amplitude