A low-loss optical switch using liquid crystal core waveguide with polymer cladding

We demonstrate an electrically controlled optical switch based on nematic liquid crystal (LC) core waveguide, fabricated on an ITO-coated glass substrate, with upper and lower cladding layers of the negative photoresist AZ15nXT. The reorientation of the LC molecules in the presence of an applied electric field produces distinct guiding properties for the TE and TM polarizations of light. Considering full anisotropy of the LC, the thickness of the cladding layer is chosen suitably to minimize the propagation loss of guided modes. The fabricated device operates at a threshold voltage of 3.5 {\rm V-{pp}}, and behaves as an optical switch for TM polarization of light with an extinction ratio > 15 dB. We experimentally achieved a relatively low insertion loss ∼7.96 dB at the applied voltage of 10 V for a waveguide of length 10 mm. The proposed device has potential application as an electrically controlled optical switch or retarder, particularly for low frequency applications.