High-resolution photothermal microscope: a sensitive tool for the detection of isolated absorbing defects in optical coatings

The photothermal deflection technique allows us to highlight the presence of inhomogeneities of absorption in optical components. This nondestructive tool is of great interest to the study of the role of contaminants, inclusions, and impurities in the laser-induced damage process. We show that the detection of nanometer-sized isolated absorbing defects requires the development of an adapted photothermal setup with high detectivity and high spatial resolution. Thus it is essential to improve the resolving power up to its theoretical limit.