Lateral-Looking Time-Resolved Thermal Wave Microscopy

Abstract

Time-resolved thermal wave microscopy was used to measure lateral thermal transport in a thin metallic film on an insulating substrate. The basis of this approach is to decompose the reflectivity signal into a component that varies with delay time and a steady state component that varies with pump modulation frequency. The transient component is a summation of thermal waves at integral multiples of the pulse repetition frequency (76 MHz). The steady state component depends only on thermal waves at the pump chopping frequency (10-100 kHz). It is shown that for long delays, the steady state component is dominant and can be used to measure the thermal diffusivity.