Optical mirror coatings are used for high-temperature diffusion barriers and mirror shaping. Certain materials for use as high-temperature diffusion barriers under optical mirror coatings include metals that have high melting and/or boiling points and amorphous and partially recrystallized inorganic amorphous materials that have high glass transition temperatures (Tg). Candidate metals are selected based upon the boiling point or a combination of melting point and boiling point. Candidate amorphous and partially recrystallized inorganic amorphous materials are selected based upon the glass transition temperature. Optical mirrors having such high-temperature diffusion barriers maintain reflectivity when exposed to elevated temperatures, and are particularly useful in optical Micro Electro-Mechanical Systems (MEMS) that are exposed to high-temperature manufacturing processes. Optical mirrors are shaped using tensile and/or compressive films.