The reflectance and transmittance of dielectric thin films at oblique angles of incidence have strong polarization effects. For some applications these effects are undesirable. A nonpolarizing beam splitter design concept is shown, which is based on the fact that in a quarter-wave stack at λ0 two effective indices that obey the Brewster condition affect only the spectral performance of the s state at λ0. This property is used as a design tool. The concept can be applied to a wide range of angles and transmittance values, with the use of effective quarter-wave layers of at least three different materials. A few examples are elaborated where these values are designed and optimized to give either Tp = Ts or Tp + Ts = constant, in the vicinity of λ0.
© 1992 Optical Society of America
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