Micrometer scale visualization of thermal waves by photoreflectance microscopy

Abstract

We propose a novel approach of photoreflectance microscopy that provides a direct visualization of the phase contour lines of the thermal wave. The method is applicable to (possibly heterogeneous) samples of mediocre polish. In a locally homogeneous region it yields the local thermal diffusivity.

Thickness-dependent thermal properties of amorphous insulating thin films measured by photoreflectance microscopy

“…It uses an intensity-modulated green laser (λ=532 nm) focused by an optical microscope onto the surface of the sample [21,29].…”

“…It is based on the generation of thermal "waves" by intensity-modulated optical excitation. This technique was first proposed by A. Rosencwaig et al [20], and then widely used to determine the thermal properties of bulk materials [21,22], grains [23], coatings and thin films [24,25]. In this work, the frequency domain photoreflectance method is used to study the effect of thickness on the thermal properties of amorphous SiO 2 and Al 2 O 3 thin films.…”

Spatially localized measurement of thermal conductivity using a hybrid photothermal technique

“…8,9 In general, a thermal wave is a nonpropagating diffusion wave defined by a complex wavenumber. 18 In this section, models of thermal waves used for data analysis will be discussed.…”

“…8,9 The amplitude and phase of the probe signal are detected using lockin amplification. However, in the remainder of the paper, we will consider only the phase profile of the temperature field.…”

“…6,7 In general, these methods use a pump laser for transient heating of the sample. This can be implemented in the frequency domain using an amplitude modulated continuous wave laser [8][9][10][11] or in the time domain using a pulsed laser. 12,13 Temperature sensing is accomplished by either recording black body radiation (laser flash) or using a probe laser to record small temperature induced changes in optical reflectivity (thermal reflectance).…”