THERMAL-STABILITY OF INPUT OPTICS ELEMENTS OPERATING IN A STRESSED THERMAL REGIME

Based on the results of solving the problem concerning the nonsteady-s tate temperature distribution in a plate cooled from the surface and f ormulas for estimating the thermal stability of a flat isotropic optic al element, it is shown that the thermal stability of the element equa ls the ratio of the values of the Kindger factor for the given materia l to the transfer coefficient of the surface of the body of the body-m edium temperature jump, which depends only on the Blot parameter Bi an d through it on the heat-output coefficient, the thermal conduction, a nd the thickness of the plate. It is shown that there is satisfactory agreement between the calculated results for the thermal stability and the experimental data for a group of polycrystalline optical material s. (C) 1997 The Optical Society of America.