Two-dimensional imaging of thermal diffusivity in metals by scanning photodeflection detection

Abstract

We present a technique that retrieves the thermal diffusivity of metallic samples in a two-dimensional map with micrometer resolution. The technique uses a photothermal method based on the deflection of a probe beam after heating the surface with a modulated pump. After adequate calibration, the time delay between the pump modulation and the deflection modulation provides direct information on the local thermal diffusivity. The calibration is carried out by measuring the frequency dependence of the deflection signal at several sample locations. The capabilities of the technique are illustrated with the measurement of a cross section of a surface treated steel sample.