Photothermal Techniques

Abstract

The first demonstrations of photoacoustic and photothermal effects were made in the nineteenth century, but the development of photothermal techniques did not really take off until the 1970s, in particular through the work of Rozencwaig [1, 2]. Today a broad range of methods can be subsumed under this heading, with the common feature that they use light to produce a thermal excitation. By extension, other methods are included, in which a light wave is used to probe a thermal phenomenon. This chapter will be concerned with the latter, and in particular their application to microelectronic technology. Indeed, insofar as they are non-contact, and generally non-invasive, optical measurement techniques are well suited to many micro- and nanoscale heat transfer problems.

This area has long been dominated by techniques involving measurement of infrared thermal emission in the far field. With the exception of recently developed methods using the near infrared, these methods have reached their limits today because their spatial resolution is not good enough to be applicable to micro- and nanoscale heat transfer. Here we shall review the main optical techniques that have emerged recently to get around these limitations. Many of them use modulation, exploiting the excellent signal-to-noise ratios that can be obtained by lock-in methods, but also spatial confinement of the modulated part of the temperature obtained under alternating conditions.