The selection of optical substrate material is a vital step to determine the best appropriate optics for your individual applications. The characteristics(optical transmission, refractive index, hardness, etc.) of representative optical materials such as N-BK7, UV Fused Silica, Zerodur Glass, Chalcogenide Glass, BaF2, CaF2, MgF2, Germanium, Zinc Selenide, ZnS, Sapphire, Silicon, alpha-bbo, calcite, YVO4, and F2 glass are introduced and compared in this article from Shalom.