Beam Displacement Rhombs

A simple, single-crystal polarizer

Beam Displacement Rhomb

This simple device, usually manufactured in calcite but also possible in just about any birefringent material such as quartz, α-BBO and MgF2, provides an elegant way of separating a beam into its two orthogonal polarization components. A beam entering a block of calcite with its input and output faces cut at 42° to the optic-axis will undergo a maximum displacement (but no angular deviation) of the extra-ordinary ray component. The effect provides a displacement of the centroid of the beam of a little over 1 part in 10 of the propagation length, thus at 1µm wavelength the displacement produced by a 10mm long rhomb will be approximately 1.05mm. Other birefringent materials may also be of use for wavelengths not covered by the transmission of calcite, an example of which would be quartz, but the displacement produced will in general be lower than that of an equivalently long calcite rhomb because of the lower birefringence of quartz.


Model Aperture
Dia (mm)
BSC-08-20 8 20 2 25
BSC-08-30 8 30 3 25
BSC-08-40 8 40 4 25
BSC-08-50 8 50 5 25
BSC-08-60 8 60 6 25
BSC-10-20 10 20 2 25
BSC-10-30 10 30 3 25
BSC-10-40 10 40 4 25
BSC-10-50 10 50 5 25
BSC-10-60 10 60 6 25


These are just sample sizes, we can also make completely custom devices at any (reasonable) aperture subject to material availability. Of course we can also offer standard or custom mounting solutions as well as anti-reflection coatings.