Glan–Foucault prism

Compared to the Glan–Thompson prism, the Glan–Foucault has a narrower acceptance angle over which it works, but because it uses an air gap rather than cement, much higher irradiances can be used without damage.

The prism is also shorter (for a given usable aperture) than the Glan–Thompson design, and the deflection angle of the rejected beam can be made close to 90°, which is sometimes useful.

The Glan–Taylor prism is similar, except that the crystal axes and transmitted polarization direction are orthogonal to the Glan–Foucault design.

[2] Calcite Glan–Foucault prisms are now rarely used, having been mostly replaced by Glan–Taylor polarizers and other more recent designs.

[3] YVO4 prisms are more expensive, however, and can accept beams over a very limited range of angles of incidence.