Polarization-independent tunable wavelength-selective filter using a liquid crystal

The authors demonstrate a polarization-independent liquid crystal Fabry-Perot interferometer. An input light beam was split into two orthogonal polarized beams by a polarization beam splitter and prism and the polarization of one beam was rotated 90 degrees by a half-wave plate. These two beams were filtered through different points of the filter and recombined. Two transmission peaks corresponding to these beams usually appeared. However, there were some regions where the two beams were superimposed. At these regions, the filter had a tuning range of over 50 nm with a band pass of 0.4-0.5 nm and a low fiber-to-fiber loss of 3 dB. At the regions where two peaks appeared, the two peaks could be superimposed by applying different voltages. >