A polarization independent liquid crystal assisted vertical coupler switch

A novel compact cascaded structure suitable for the realization of a 2 × 2 polarization independent integrated optical switch using liquid crystal is reported. The switch consists of a vertical coupler formed by two Ag +-Na + ion-exchanged single-mode channel waveguides diffused in two BK7 glass substrates of a liquid crystal cell, The coupling properties, and thus the switching state (bar or cross), of this structure can be controlled by electrically reorienting the director of the aligned liquid crystal layer. The device was simulated and optimized at λ = 1550 nm by using a beam propagation method algorithm. Calculated crosstalk attenuation and losses of an optimized TE switch with the TE 00 mode propagating in the input waveguide are 42.5 dB and 0.49 dB respectively with a coupling length of 141 μm. A TM switch, with the TM 00 propagating mode, exhibits a crosstalk attenuation of 37.7 dB and losses of 1.42 dB with a coupling length of 127 μm. Estimated average crosstalk attenuation and losses of a polarization insensitive cascaded switch are 39.7 dB and 0.93 dB respectively. The evaluated driving voltage magnitude required for the switching operation results below 20 V.