Editorial Feature

Pellin-Broca Prism - Definition and Uses

A Pellin–Broca prism is a type of constant-deviation dispersive prism. It is named after its inventors, Ph. Pellin - a French instrument maker - and André Broca - a professor of physiological optics.

To form the Pellin–Broca prism, an ordinary dispersing prism is divided in half along the bisector of the apex angle. The two halves are joined together using a right-angle prism, so as to create a dispersing prism with an internal right angle bend, achieved by total internal reflection.

A Pellin-Broca prism’s output is always taken at 90° to the input direction. The wavelength transmitted differs, as the prism is rotated. It operates at Brewster`s angle for 240nm and has very high transmittance throughout the spectrum.

A Pellin-Broca prism can be custom-made in many sizes and materials, and in spectrums from UV through to the visible wavelengths to suit specific functions.

The Pellin–Broca prism is often used in monochromators, laser-line selector, and optical atomic spectroscopy. It is used to separate a single required wavelength from a light beam that has multiple wavelengths.

Sources and Further Reading

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