Dispersing prisms

Dispersing prisms have three 60° angles, so are also referred to as equilateral prisms. These provide an advantage over diffraction gratings when a higher-order diffraction effect is unwanted.

Typical applications for dispersing prisms are for wavelength angular separation, whereby the prism is placed in a beam path to refract the beam twice. A common method is to use the prism                minimal deviation angle, achieved by aligning the wavelength of interest to travel in parallel to the prism base.

This ensures that the angles of incident and refracted beams are equal with respect to the corresponding surfaces. This alignment provides the benefit of a maximum clear aperture and the least         overall reflection loss for p-polarization.

Dispersing prisms are well known in pop culture from Pink Floyd’s album “The Dark Side of the Moon”, the iconic cover of which shows a dispersing prism separating white light into the colors of            the rainbow.