Sapphire Windows, often called Sapphire Glass Windows or Sapphire Optical Windows, made of single crystal synthetic sapphire (Al2O3), are becoming more and more indispensable in the exclusive fields of electro-optics due to their combination of superior optical, chemical, and mechanical properties. This article that Shalom EO presents concentrates on the optical transmission and the optical properties of sapphire windows, including the transmission wavelength range of sapphire, the transmission rate, the birefringence, and orientations. We have also analyzed the different growth methods and grades of sapphire crystals.