Determination of the optical absorption coefficient via analysis of laser-generated plate waves

A technique has been demonstrated which measures the optical absorption coefficient in weakly to moderately absorbing homogeneous isotropic elastic plates. This technique involves generating plate waves with a pulsed Nd:YAG laser and then detecting the disturbances in the acoustic far field where the majority of the acoustic energy has been coupled into the first symmetric, s/sub o/, and antisymmetric, a/sub o/, plate modes. The optical absorption coefficient is determined by comparing the experimental and theoretical expression for the ratio of the integrated power spectra of the s/sub o/ and a/sub o/ modes.