This paper describes the transient temperature gradients in multilayer optical thin films when subjected to high energy continuous wave and repetitive pulsed lasers. Equations are described for use in evaluating the time-temperature history of each coating interface and subsequent energy distribution to the substrate. One and three dimensional equations are provided to examine the impact of thermal diffusivity, relaxation time and subsequent damage to the optical thin films. Coatings that are supported by cooled substrates are evaluated as a function of substrate material and cooling medium heat transfer coefficient. Coating temperatures and substrate temperatures are evaluated for conditions satisfying the semi-infinite plate model. A substantial number of curves are generated to provide the reader with an equation relationship of the response of the various coating and substrate materials. Key words: High Energy Laser, Optics, Optical Thin Films, Heat Transfer, Laser Damage.
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