Pulsed photoacoustic technique to measure the absorption coefficients of the highly transparent optical materials

A new technique of measuring the low optical absorption coefficient is described by using pulsed photoacoustic calorimetry. The frequency dependence of the photoacoustic signal is different owing to its main origin, either the bulk absorption or the surface absorption. The Fourier transform of the pulsed photoacoustic signal, generated by a pulsed CO₂ laser, is obtained as the frequency response of the photoacoustic signal. The ratio of the bulk absorption coefficient and surface absorption coefficient is acquired as 1:1.5.