Reflectance analysis of a multilayer one-dimensional porous silicon structure: Theory and experiment

We present a method for treating birefringent effects in layered media and apply the formalism to analyze reflectance from a multilayer one-dimensional (1D) porous silicon (PS) structure at off-normal incidence. The approach is to characterize the fields in terms of s- and p-polarized amplitudes in each layer, and the calculations then naturally employ Fresnel reflection and transmission coefficients for the uniaxially anisotropic media. We observe an excellent agreement between the theoretical and experimental curves by including optical absorption and macroscale waviness of the PS layers, and the resolution of the spectrophotometer. In particular, we point out the importance of birefringent effects that cause the splitting of the resonance wavelengths between two different polarizations. The investigated 1D PS structure can be used, for example, as a polarization sensitive optical switch.