Abstract: Sapphire is an ideal optical material and is in used for window and dome applications. The anisotropic properties of sapphire affect the production of high-quality components. Out of the three major orientations, c-axis, a-axis or m- axis, the c-axis is preferred for optical applications as it is the zero birefringence orientation. This orientation is difficult to grow with high quality. Therefore, components are fabricated by sectioning from the sides of a- or m- boules. The anisotropic properties also present problems in grinding and polishing windows for precision optical applications. The degree of difficulty varies with the orientation selected. For hemispherical domes involving polishing of several orientations, it is difficult to achieve a good figure. The choice for larger diameter windows is limited to a- or m-orientation; the m-orientation may be preferable due to the geometry of fabrication-induced stress. !9
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