A polarizing beamsplitter cube consists of two right angle prisms cemented together. The hypotenuse face of one prism is coated with a special multilayer dielectric coating. When circularly polarized or natural light enter the cube vertically, it separated into two linearly polarized beams. The transmitted beam is P-polarized while the reflected beam is S-polarized.
And when a linearly polarized light come in, it similarly divided into two beams. But the energy ratio of the two outgoing beams is depending on the polarization of the incident beam. Polarizing beamsplitter cubes are available for many laser wavelengths and broadband ranges.