Birefringent Beam Displacers

A birefringent beam displacer is made from a plane parallel plate with the crystalline optic axis lying at an angle to the surface normal. Light polarized perpendicular to the optic axis is transmitted without displacement while light polarized along the plane in which the optic axis lies, walks-off a distance determined by the refractive indexes, the angle , and the thickness of the plate.
 

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