Effect of TiO2 nanoparticle doping on the performance of electrically-controlled nematic liquid crystal core waveguide switch

• We have studied switching characteristics of the LC core waveguides, realized using nanocolloids of the nematic LC 5CB.
• The electro-optic characteristics of TiO2 doped 5CB LC core waveguides have been experimentally investigated.
• As the TiO2 doping concentration is increased, the dielectric anosotropy increases, and the screening effect of the alignment layer is reduced; this leads to a lower threshold voltage for the LC core waveguide switch.
• Study of the propagation characteristics of TE and TM polarizations in the doped LC core waveguides with different doping concentration, indicate that the optimal performance, in terms of lower threshold and differential attenuation, is obtained for 0.5 wt.% TiO2 doped LC core waveguide.

A liquid crystal (LC) core waveguide has been designed and fabricated using nanocolloid of the nematic liquid crystal 5CB, doped with TiO2 nanoparticles, as the core. Nematic liquid crystals doped with small amount of nanoparticles can have significantly altered electro-optic response. The performance of the fabricated LC core waveguide as an optical-switch has been studied, and the experimental result shows that the threshold voltage for switching is reduced from 1 V to 0.25 V due to TiO2 nanoparticle dopant-concentration of 2.0 wt.%. The overall optimal performance of the waveguide switch, in terms of threshold voltage, extinction ratio, and response time, is achieved for a dopant-concentration of 0.5 wt.%.