Introduction to photothermal detection schemes

Photothermal techniques, which all rely on the conversion of light to heat have attracted a great deal of interest since the first demonstrations by Bell over 100 years ago. Although it may seem counterintuitive to pursue phenomena based on the transformation of energy to the most chaotic form, heat, these techniques have many advantages for applications in low absorption environments and in the domain of materials characterization and nondestructive testing. For instance, in low absorption measurements we can reach detection limits on the order of 1:10-12, as the signal is directly related to the small quantity of energy absorbed, while in nondestructive testing, we make use of the fact that we may perform depth profiling by varying the modulation frequency.

Photoreflectance, IR radiometry, and Mirage Effect detection serve as good examples due to the flexibility of these techniques. This flexibility has been demonstrated in domains as practical as on site non-destructive testing of commercial aeronautic equipment and as fundamental as metrology of optical components, passing by exciting new topics such as characterization of diamond films and semiconductor devices as well as environmental monitoring. We wish to present here both a general overview of how optical detection of Photothermal excitation can be used in a variety of experimental schemes, as well as specific details of technical applications based on work which is well know to us. We have decided to focus on applications, instead of presenting too many details of the theory, in an effort to demonstrate the specific advantages of the individual techniques and to better illustrate the principles involved, and will compare works which illustrate the choices available. We hope in this way to present the most important points of the present state of the art for the researcher who wishes to evaluate Photothermal detection schemes for his own applications based on the specific advantages they offer. We also hope to provide sufficient references to other published resources, so that one may continue where we have, in the interest of brevity, left off.

The Mirage Block/Le bloc Mirage

Mesoscopic IR radiometry/La radiométrie mesoscopique IR


Reflectometry/La réflectomètrie

Additional PA/PT resources/Resources PA/PT

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