Numerical investigation of a nano-scale electro-plasmonic switch based on metal-insulator-metal stub filter

Abstract

We present a nano-scale electro-plasmonic scheme operating at 1550 nm based on plasmonic Metal-Insulator-Metal waveguide and stub filter configuration. The linear dependency of the transmission spectra of the stub filter to the length of the stubs allows designing a switch that works as normally ON or OFF switch by selecting the length of the stubs 300 or 410 nm, respectively. In our proposed waveguide-based structure, the core is an electro-optic material known as 4-dimethyl-amino-Nmethyl-4-stilbazolium tosylate with the refractive index 2.2 while the metal cladding is silver. Three-dimensional Finite Element Method simulations demonstrated that by applying a 10 V voltage to the silver cladding, a red-shift in the transmission spectra of the filter leads to turn the switch OFF or ON with calculated extinction ratio $-13.83$ and 11.81 dB, respectively. The calculation of the capacitance implies that the switching rise-time of the switch is less than 20 fs and the bandwidth is far beyond the 18 GHz. At the maximum dimension $460\,\hbox {nm}\times 450\,\hbox {nm}$, the subwavelength size of the switch promises the potential for future compact integrated plasmonic circuitry. For the verification of three dimensional simulation results, we have tried it, using two-dimensional transmission line method for modeling the stub filter, which demonstrates a reasonable accuracy in comparison with three-dimensional finite element method.