Measurement of periodic surface heating using surface acoustic waves

Abstract

A new technique is described to measure periodic heating at and near the surface of a material. The technique involves the phase perturbation of a surface acoustic wave propagating through the heated region. Temperature fluctuations can be measured at modulation frequencies of several hertz to hundreds of kilohertz with high sensitivity. A theory is given which predicts the acoustic phase perturbation as a function of thermal modulation frequency, and is shown to agree well with experiment.