Thermoreflectance technique to measure thermal effusivity distribution with high spatial resolution

We have developed an apparatus to measure thermal effusivity distribution in solid materials with a high spatial resolution better than 10 μ m by the thermoreflectance technique and the periodic heating method. A metal film sputtered on the surface of a sample is periodically heated by a modulated laser beam. The temperature response is measured by using another thin laser beam as a thermoreflectance signal. The thermal effusivity of the sample is derived from the phase lag of the temperature response from the periodic heating. Measurements of a functionally graded material and a fiber composite material are presented as application examples of this thermal effusivity distribution measurement technique.