Glan–Taylor prism

The Glan- Taylor prism ( Glan by Paul Taylor and AM ) is based on total reflection, birefringence and polarizer, the non-polarized light is linearly polarized (p- polarized, i.e., the Polarisationssebene is in the plane of incidence ). The principle was introduced in 1880 by Paul Glan and improved by AM Taylor 1948.

The Glan- Foucault prism is constructed basically the same as the Glan- Taylor prism, but the section is rotated by 90 ° relative to the optical axis of the calcite. This has the result that the transmitted beam is s-polarized.

Construction

The Glan -Taylor prism is similar to the earlier ( 1828) developed Nicol prism of a birefringent crystal ( calcite, typically ), which is cut along the diagonal plane parallel to the optical axis. The two halves are not joined directly, an air gap between the prism elements provides interfaces to an optically thinner medium.

Operation

Upon entry into a material of the incident light beam is refracted according to the Snell's law of refraction. Because of the anisotropic refractive indices of birefringent materials, the incident beam will behave differently depending on its polarization direction. One distinguishes the ordinary ( normal to the optical axis of the crystal polarized ) and extraordinary ( polarized parallel to the optical axis ) beam. Upon incidence oblique to the optical axis, for example, when Nicol prism, the rays are refracted to different degrees. The Glan- Taylor prism, the two calcite prisms are ground so that the cut faces of the crystal are parallel to the optical axis. In this way it is prevented that after refraction of the incident beam, the ordinary and extraordinary beams have different angles of refraction. At normal incidence, the two beam components so move on a common path in the crystal, although due to the different refractive indices at different speeds.

The angle of intersection of the two prism halves is now chosen so that the ordinary ray is totally reflected at the interface ( for the ordinary ray, the air in the gap compared to calcite an optically thinner medium DAR) and the extraordinary ray is transmitted. This is achieved, as the refractive index for the ordinary ray is larger than for the extraordinary and since also the angle of incidence corresponds to the interface about the Brewster angle. The second (shown right ) prism is used only for compensation of the beam deflection. Upon exiting the crystal, therefore, is present only the extraordinary linearly polarized beam whose polarization plane is the plane of incidence and the direction opposite to the incident direction is changed.

Demarcation from other prism types

Which is also very similar structure Glan-Thompson prism ( is more like a Glan -Foucault prism, with a transparent adhesive rather than air ) is generated as the Glan -Foucault prism, a 90 ° different polarized beam (s- polarized).

Lippich the prism ( according to F. Lippich ) has the same orientation of the optical axis as the Glan- Taylor prism, but has no air gap, but the two prism parts have been joined using a transparent adhesive to each other.