Design and fabrication of a liquid crystal retarder for the mid- and far-infrared wavelength ranges

We designed and fabricated a liquid crystal (LC) retarder that operates within mid-infrared (MIR) and far-infrared (FIR) wavelength regions. Fluorine-based mixed LCs and BaF2 substrates were employed to assemble the LC retarder on the basis of their absorption spectra. A thin NiCr film, which served as a semitransparent electrode in the infrared region, was also formed on the BaF2 substrate. The fabricated LC retarder showed transmittances of 40% and 42% at wavelengths of 3.88µm and 9.5µm, respectively. Here, we demonstrated phase shift that can be electrically controlled to exceed π/2. Our LC retarder can be applied to the polarization modulation in the MIR and FIR wavelength regions.