Pellin–Broca prism

The prism is named for its inventors, the French instrument maker Ph.

Pellin and professor of physiological optics André Broca.

As the prism is rotated around an axis O, the line of intersection of bisector of ∠BAD and the reflecting face BC, the selected wavelength which is deviated by 90° is changed without changing the geometry or relative positions of the input and output beams.

[2] The prism is commonly used to separate a single required wavelength from a light beam containing multiple wavelengths, such as a particular output line from a multi-line laser due to its ability to separate beams even after they have undergone a non-linear frequency conversion.

For this reason, they are also commonly used in optical atomic spectroscopy.