RetroreflectorsRetroreflectors reflect an image or beam back 180° toward its original direction. Prisms achieve this either through total internal reflections (TIR) or specular reflections, depending on whether the reflective faces are coated. "Hollow" retroreflector mirrors employ first-surface specular reflections in order to eliminate dispersion, chromatic aberrations, and material absorption inherent in prisms.
Thorlabs offers a variety of free-space optics, including retroreflector prisms and mirrors (a.k.a. corner cubes), a lateral transfer retroreflector, hollow roof mirrors, right-angle (a.k.a. porro) prisms, and Dove prisms. Fiber optic retroreflector patch cables reflect light input through the connector backward through the fiber and can be used to create a fiber interferometer or to build a low-power fiber laser.