Beam splitters for p-polarized light using a high-index quarter-wave layer embedded in a low-index cube prism

A high-index quarter-wave layer (QWL) embedded in a low-index cube prism is designed to achieve 50%-50% beam splitting for incident p-polarized light at a 45° angle of incidence. This is accomplished when the ratio of the refractive index of the QWL to that of the prism is n=3.336666. Such a refractive index ratio is realized, e.g., with a Ge QWL embedded in a LiF cube at 8.357 μm wavelength. Spectral, angular, and film-thickness sensitivities of this mid-IR beam splitter (BS) are presented. Free-standing QWL pellicles of GaP and GaAs can also function as 50%-50% BSs for incident p-polarized light at 45° at visible and IR wavelengths of 0.610 μm and 2.929 μm, respectively. An application in interferometry is briefly discussed.