Polarization-insensitive wavelength selection in an axially symmetric liquid-crystal Fabry-Perot filter

A polarization-insensitive, electrically tunable Fabry-Perot filter (FP) with a nematic liquid crystal (NLC) is demonstrated in an axially symmetrical configuration. Due to the axial symmetry, the wavelength-selection property of the FP filter is completely independent of the polarization state of the input beam in the whole range of tuning. For normal incidence, the in-plane symmetry of the input polarization state is preserved in such configuration that the alignment of the NLC molecules are homeotropic on one mirror surface and axially homogeneous on the other surface.