The refractive indices, and birefringence, of some common nematic liquid crystals are measured in the millimeter waves region mainly at 30 GHz. All liquid crystals measured had reasonably large birefringence in the range of 0.1 to 0.17. A proof of concept millimeter wave phase shifter was demonstrated based on magnetic field alignment of liquid crystal. Potential advantages of using liquid crystals in the millimeter wave range for device applications are discussed.
K. C. Lim,
J. David Margerum,
"Liquid-crystal optical properties and applications in the millimeter-wave range", Proc. SPIE 1815, Display Technologies, (27 October 1992); doi: 10.1117/12.131304; https://doi.org/10.1117/12.131304