Proceedings PaperTheoretical Model For Evaluating Transient Temperature Distribution In Rugate Optical Thin Film Coatings Subject To High Power Continuous Wave And Repetitive Pulsed Lasers
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There is, presently, a great deal of experimentation going forward on the use of rugate coating techniques. In the simplest form, a rugate coating is composed of a single material wherein the disposition conditions are modified to change the index of refrac-tion. Ideally, one achieves a homogeneous material wherein there are no severe discontinuities similar to that found in a multilayer optical stack. Because the material appears to be homogeneous, it is argued, the coating is much more thermally coupled to the substrate, thereby obviating the mechanical bonds of a multilayer stack and the subsequent thermal resistances of the interfaces. Based on the theoretical model described by Palmer 1, the rugate coating temperature gradient may be evaluated as a function of the electric field standing wave and the absorption distribution. The transient conduction and subsequent temperature buildup for one dimensional and three dimensional models will be described. The mathematical techniques are reviewed for both continuous wave laser power and for repetitive pulsed laser power. Key words: High Energy Laser, Optics, Optical Thin Films, Heat Transfer.