DESIGN ANALYSIS OF A BEAM SPLITTER BASED ON THE FRUSTRATED TOTAL INTERNAL REFLECTION

In this work, a theoretical analysis on the design of the beam splitter (BS) based on the frustrated total internal reflection (FTIR) is made. We consider a model structure made of a low-index gap layer bounded by two high-index layers. In the design of a 50/50 BS, we find that there exists a critical gap thickness which is a decreasing function of the angle of incidence for both TE and TM waves. There also exists a critical wavelength for the incident wave, and it increases with increasing angle of incidence. Finally, at a fixed gap thickness and wavelength of incident wave, the critical angle in $TE$ wave is slightly larger than that of $TM$ wave. The analysis provides some fundamental information that is of particular use to the design of a BS within the framework of FTIR.