Does the polarization of light change when it passes through a beamsplitter?

The polarization of light is changed when it is incident on a beamsplitter oriented at 45 degrees. For randomly polarized input light, the S-polarization state is reflected more than the average amount of reflection and the P-polarization state is reflected less than the average. Plate beamsplitters are very sensitive to polarized light, the transmission of the S- and P-polarization states can each vary typically as much as 20% from the average at 550nm for a visible spectrum coating. Our dichroic cube beamsplitters are also extremely sensitive to polarization. The S- and P-polarization states can have a difference as large as 70%, while each differing from the average transmission by approximately 20-30%. Beamsplitters should be selected carefully prior to integration into polarization sensitive applications. We do offer polarized cube beamsplitters that offer 92% reflection for S-polarization at 632.8nm.