Efficient tunable plasmonic mode converters infiltrated with nematic liquid crystal layers

Abstract

This paper presents two efficient tunable plasmonic mode converters in the infrared regime. The proposed configurations consist of silver layer with etched rectangular holes as metal insulator metal (MIM) waveguides with central cavities. The holes are infiltrated by nematic liquid crystal (NLC) material to increase the transmission through the suggested designs. Additionally, the NLC is used to have tunable operation where the modes at the output port can be controlled. The simulations are carried out using full vectorial finite element (FEM) method. The first design has a single output port which converts the TM mode into the TEM mode with high transmission conversion efficiency of 70%. Further, the second structure allows the generation of the two plasmonic modes simultaneously in two output waveguides. During the biased state, the s-mode transmission conversion efficiency reaches 50% while the transmission of a-mode at the unbiased state is equal to 49%. It is expected that the proposed tunable mode converters will play an important role in the development of the plasmonic-photonic circuits.