Photoacoustic technique for determining optical absorption coefficients in solids

Abstract

An investigation was made of a photoacoustic technique for determining the optical absorption coefficient in solids. A train of laser pulses was passed through the solid, and a piezoelectric transducer attached directly to the sample measured the amplitude of the elastic wave generated by the absorbed radiation. Calibration was performed at a wavelength of known absorption. The sensitivity of the technique was found to be limited to about 1 × 10⁻⁵ cm⁻¹ in our samples due to radiation scattered onto the transducer, but the technique is capable of measuring absorption coefficients in the 10⁻⁶ cm⁻¹ range using laser powers of about 1 W.