Designs of infrared non-polarizing beam splitters

When used at oblique angles of incidence, the reflectance and transmittance of thin films exhibit strong polarization effects (PEs), particularly for the films inside a glass cube, which result from the fact that the tangential components of the electric and magnetic fields are continuous across each layer interface. However, for many applications, the PEs are undesirable and should be reduced. Therefore, the concept of non-polarizing beam splitter (NPBS) is proposed. Up till now, however, most of the reports of NPBSs are suitable for visible light. Therefore, it is necessary to find out some methods to reduce the PEs for infrared applications. A design method of the infrared NPBS in a cube is proposed, the theoretical analysis is given, designs for different substrates are demonstrated and the simulations of their optical properties are presented in this paper.