Abstract: An improved prism which polarizes and retroreflects a light beam which is incident thereto at the Brewster's angle. The principles of the Brewster window, corner reflector, and total internal reflection, such as at the ends of a laser cavity, is incorporated into a single optical device. When correctly polarized light, with respect to the Brewster angle entrance to the prism, strikes the specially shaped right angle prism at the Brewster's angle, the light will be retroreflected straight back paralled to the incoming beam without significant losses.