Low threshold optical attenuator based on electrically tunable liquid crystal cladding waveguide

We propose a multimode planar waveguide with polymer core of negative photoresist AZ15nXT with an upper cladding of electrically tunable 4-cyano-4'-pentylbiphenyl (5CB) nematic liquid crystal. The waveguide is realized on indium tin oxide (ITO) coated glass substrates using a simple, cost-effective photolithography fabrication technique. The refractive index of LC cladding changes with the applied voltage, which affects the propagation of transverse magnetic (TM) modes of light in the core. We experimentally achieved a relatively low threshold voltage of 1.08 V and the maximum required operating voltage of 4 V-pp (peak to peak) at 633 nm wavelength. An extinction ratio of 12 dB for TM modes is obtained at an applied voltage of 4 V-pp. A theoretical and experimental analysis is done to present the device as a low threshold electro-optic switch and optical attenuator for TM polarization.

Automated summary

We propose a multimode planar waveguide with a polymer core and an electrically tunable liquid crystal cladding. The waveguide is fabricated using a cost-effective photolithography technique. The refractive index of the cladding can be controlled by applying voltage, which affects the propagation of TM modes in the core. Experimental results show a low threshold voltage and a high extinction ratio, making this device suitable for low threshold electro-optic switching and optical attenuation.