An overview of the application of the photothermal technique for optical as well as thermophysical characterizations of thin films is given. The peculiarities of this technique are discussed in some detail, and selected important results are pointed out. Emphasis is placed on the influence of both residual absorption and randomly distributed inhomogeneities in thin films on their laser-damage resistance.

We report on reflection gratings produced entirely of dielectric materials. This gives the opportunity to enhance the laser damage threshold over that occurring in conventional metal gratings used for chirped-pulse-amplification, high-power lasers. The design of the system combines a dielectric mirror and a well-defined corrugated top layer to obtain optimum results. The rules that have to be considered for the design optimization are described. We optimized the parameters of a dielectric grating with a binary structure and theoretically obtained 100% reflectivity for the -1 order in the Littrow mounting for a 45 degrees angle of incidence. Subsequently we fabricated gratings by structuring a low-refractive-index top layer of a multilayer stack with electron-beam lithography. The multilayer system was fabricated by conventional sputtering techniques onto a flat fused-silica substrate. The parameters of the device were measured and controlled by light scatterometer equipment. We measured 97% diffraction efficiency in the -1 order and damage thresholds of 4.4 and 0.18 J/cm(2) with 5-ns and 1-ps laser pulses, respectively, at a wavelength of 532 nm in working conditions.

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The precise determination of the absolute absorptance of a laser component is of high scientific and commercial importance. Our intention is to demonstrate that laser calorimetry can be a reliable and sensitive characterization tool for this purpose. Furthermore, the limitations of laser calorimetry are discussed and suggestions for possible revisions of the ISO 11551 (International Organization for Standardization, Geneva, Switzerland) standard are made. Finally, laser calorimetry is compared with photothermal deflection methods with respect to their practicability in different fields of laser optic characterization.

A mode-mismatched surface thermal-lens technique with pulsed top-hat beam excitation and a near-field detection scheme are developed to measure in situ the thermoelastic response of ultraviolet dielectric coatings to excimer-laser (193- or 248-nm) irradiation. The thermal-lens technique is demonstrated to be not only convenient for accurate determination of the laser-induced damage threshold (LIDT) but also sensitive to measurement of the thermoelastic response of dielectric coatings irradiated with fluence far below the LIDT, and hence is shown to be appropriate for time-resolved predamage investigation. A minimum detectable surface displacement of approximately 0.002 nm is achieved with a simple experimental configuration. Nonlinear absorption as well as the nonlinear effect in laser conditioning of a LaF(3)/MgF (2) highly reflective dielectric coating are observed for what is believed to be the first time.