Equilateral optical prism
CVI Melles Griot
Reflection losses are minimized for unpolarized rays traveling parallel to the base of the prism. This condition is called minimum deviation.
Minimum deviation occurs when the ray and wavelength angle of incidence at the entrance surface are equal to the angle of emergence (both angles measured with respect to the surface normals).
Prisms are available in N-BK7, N-F2 and N-SF10 glass as well as UV-grade fused silica.
Antireflection coatings help reduce polarization at the prism surfaces by increasing total transmittance.