Electrically driven flexible 2D plasmonic structure based on a nematic liquid crystal

A novel 2D active plasmonic grating based on liquid crystal (LC) infiltration is demonstrated and theoretically analyzed, by combining the plasmonic properties of the gold nanostructure and the optical properties of the liquid crystal. In this structure, a thin layer of E7 liquid crystal was typically injected onto a gold nanostructure, deposited on a polydimethyl siloxane substrate, using nanoimprint lithography method. The surface plasmon resonance of the fabricated plasmonic structure can be controlled by changing the refractive index of the LC, which was achieved with an external electric field. LC molecules confined between the gold nanostructure and an indium-tin-oxide glass are randomly aligned, and they can exhibit a reversible refractive index, depending on their orientation under the external voltage and the polarization of the incident light. Both theoretical and experimental results demonstrate that the wavelength of the resonance peak can be red shifted by the electric field-dependent refractive index of the LC. This experimental work provides us an active control of surface plasmon resonance using LC which can act as an ideal active medium for different applications such as a low voltage sensor with a sensitivity of 0.4375 nm V-1.