Polarization beamsplitter cubes are constructed by cemented two right angle prisms. 

►The hypotenuse of one prism is coated with polarization dielectric coating.
The absorption loss of dielectric coating is negligible.

►When used with normal incident, un-polarized light , the incident beam is separated into
two polarized beams. The beam that pass straight through the cube is linearly p-polarized.
The beam that emerges from the cube at right angle to incident beam is S-polarized.

►When used with linearly polarized incident beam,  the beam is similarly  divided. The
ratio of the emergent beam depend on the orientation of the incident beam electric field
vector.

A pair of polarization beamsplitter cube in identical orientation can be used to get greater extinction.
  The resulting extinction ratio is the square of single cube.

Principle Transmittance: Tp>95% and Ts<1%

Principle Reflectance: Rs>99% and Rp<5%