Characterization of optical coatings by photothermal deflection

Abstract

An overview of photothermal deflection principles and applications is given. The modeling of temperature distribution and the calculation of deflection that is due to both the refractive-index gradient and the thermal deformation of the sample are presented. Three configurations usually employed are compared, and their respective advantages are discussed in relation to their application. The calibration for absolute measurement of absorption is detailed, showing that calibration limits the accuracy of measurement. Some examples of specific information obtained by photothermal mapping of absorption are given.

Study of luminescent defects in hafnia thin films made with different deposition techniques

“…For better-quality coatings a spatially resolved approach can provide more interesting data as has been shown in recent studies on model materials like silica with embedded gold nanoparticles [11]. Furthermore, we will show in this section that different kinds of defects may be identified using simultaneous mapping of photothermal deflection, wavelength-integrated luminescence and the scattering signal.…”

Laser Resistant Coatings

“…Photothermal microscopy (see also chapter "Characterization and Monitoring" by Ristau) is a useful tool for evaluating the thermal characteristics of coating defects described in Sect. 4 (Commandre and Roche 1995). The magnitude of observable scatter from defects does not correlate well with damage susceptibility (Fomier et a!.…”

Engineering meter-scale laser resistant coatings for the near IR

“…Photothermal microscopy experiments clearly illustrate that some defects with significant absorption may not be optically visible as opposed to nodular defects with diameters up to tens of microns in diameter that are easily observed with an optical microscope. [14][15][16][17][18] Post mortum focused-ion beam cross section (figure 2) inspection of these defects revealed in one particular study, 14 these defects had such low laser resistance that they were damaged by the pump beam of the photothermal microscope. Analysis of these images suggested a very small initiator that caused thermal-induced buckling of the surrounding multi-layer structure.…”