Generation of acoustic pulses of short duration from laser pulses on metal foils

Abstract

To calibrate transducers in water, a laser was used as a means to generate acoustic pulses of short duration. In the experiments, samples were chosen from the available metal foils (stainless steel and aluminum) with different thicknesses. Several conclusions can be drawn from the experiments. (1) The energy density of the incident laser pulse has a strong effect, depending on the properties of sample, on the duration of the generated acoustic pulses. (2) Thermal expansion β and thermal diffusivity length L are two important parameters that affect the generated acoustic waveforms, where L = (2Dtρ)1/2 and D = K/cρρ, K is the thermal conductivity, cρ is the specific heat, ρ is the density, and tρ is the duration of a laser pulse. (3) If the thickness of a sample is comparable to the thermal diffusivity length L, it will affect the generated waveform. (4) Laser generation of acoustic pulses from metal foils may be able to be used to calibrate receiving transducers in a liquid, at least in a relative sense. [...