Design of an Optical Switch and Sensor Based on a MIM Coupled Waveguide Using a DNA Composite

A switchable surface plasmon polariton optical coupled waveguide made by exploiting a DNA composite is proposed in this paper. The switchable DNA element is used for controlling the electric field and transmission line shape. A multiband resonance is obtained for transmission to improve the optical sensing performance. Here, dumbbell-shaped cavity slots are utilized to control the effective length, with two resonances at 960 and 1260 nm for the low-conductivity mode, while there is one peak at 1590 nm for the high-conductivity mode. The DNA element is placed between two conductive silver lines, and thus acts as a switch. The structure can be controlled by switching between the DNA composite conductivity modes, and this ability can be considered for optical gates or switches at 960 and 1500 nm. The resulting switching factor is about 450 at 960 nm. The frequency shift and variation in full width at half maximum are evaluated as two functions for obtaining the sensitivity and figure of merit (FOM) of the refractive index. Therefore, this optical waveguide can be used both as an optical switch and as a refractive index (RI) sensor, with sensitivity of about 1260 nm/RIU and FOM of 120 RIU-1.