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K Prisms

K Prisms

K prisms rhombs generate a phase shift of a quarter wavelength based the phase difference between the s-polarized and the p-polarized component in total internal reflection. Similar to Fresnel rhombs Fresnel-Rhomben the path difference shows only a small variation with the wavelength and the prisms are useable over very broad spectral ranges.

K prisms do not introduce a beam displacement for light on the optical axis. Consequently, the beam position strays constant even if the application requires a rotation of the prism.

A K prism is assembled from two halves which are connected by optical contact. The contact line between the prisms is located at the center of the clear aperture. The edges of the prisms are not chamfered yielding a hardly visible contact line.

We manufacture K prisms from fused silica and from N-BK7. The prisms are delivered in a cylindrical holder and without antireflection coating.

Optical specifications

Art. No., RFK 200 RFK 400
spectral range 215-1700 nm 350-2250 nm
material fused silica N-BK7
deviation of retardation ±4% ±2%
wavefront distortion < λ/10 < λ/10
prismatic deviation <15'' <15''
reflectivity ca. 3,5% ca. 4%
temperature coefficient* a/R0(typ.) 10ž10-6/K 2ž10-6/K
tilt sensitivity** max. angle of incidence typ. 1° max. angle of incidence typ. 1°

* Definition ** K prisms are quite sensitive to tilt and show a qualitative difference compared to birefringent retarders. Therefore, the angular coefficient is not meaningful for K prisms.

Standard dimensions

215-1700 nm 350-2250 nm
Art. No.,
RFK 200 RFK 400
free aperture [mm] 9,5 9,5
mount diameter [mm] 30 30
mount length [mm] 92,5 92,5
connection diameter [mm] 25 25

Wavelength dependence of the retardation

K Prisms


order no. 1 piece in € 2 piece in € 3-5 piece in €
RFK 200 1870.- 1736.- 1603.-
RFK 400 1592.- 1479.- 1365.-
option order-no.: additional price
antireflection coating --- on request