An Electrically Controlled Nematic Liquid Crystal Core Waveguide With a Low Switching Threshold

We demonstrate an electrically-controlled liquid crystal (LC) core waveguide, using 4-cyano-4'-pentylbiphenyl (5CB) nematic liquid crystal, fabricated on a glass substrate. A negative photoresist, AZ15nXT layer was coated on the glass substrate to realize a channel waveguide of core thickness 4.8 μm. The LC core waveguide exhibits strong differential attenuation for propagation of the TE- (horizontal) and TM-like (vertical) polarizations of light. The experimental results show that the output power suddenly drops down by several dB at an applied voltage of 1 V, for a waveguide of length 10 mm, due to the re-orientation of the LC molecules. The waveguide can be used as an optical switch, as well as an optical attenuator.