Brewster Window is a special optical component designed to allow light of a specific polarization state to pass through at a specific angle (Brewster angle) without reflection loss. Brewster's angle is the angle at which light is incident from one medium to another, transmitting only polarized light without any reflection loss. This type of window is widely used in laser design, especially in gas lasers and certain types of solid-state lasers, to reduce losses within the laser resonant cavity. The design of Brewster window requires a very precise determination of Brewster angle, which depends on the refractive index of the window material. Common materials include quartz, sapphire, etc,