Experimental aspects of photothermal radiometry

Abstract

In photothermal radiometry (PTR), the thermal response of a given sample to time-varying illumination is detected via concomitant thermal radiation emanating from the irradiated region, to obtain spectral, structural, and other types of information about the sample. Excitation of the thermal response may be achieved in one of several different pulsing modes, with detection of the thermal reradiation over a wide range of wavelength bands, power levels, and frequencies. To fully exploit the power and versatility of PTR, therefore, it is necessary to choose judiciously the experimental conditions and equipment appropriate in each analytic situation. We discuss general physical aspects of PTR, emphasizing fundamental principles and methodology related to the detection of thermal reradiation. As will be shown, PTR lends itself well to explicit numerical analysis, greatly aiding the design and interpretation of experiments. Particular features relating to the investigation of high-temperature objects will be discussed. A case study is presented on the analysis of thin films on metallic surfaces, at ambient and at elevated temperatures.