Highly Sensitive Reconfigurable Plasmonic Metasurface with Dual-Band Response for Optical Sensing and Switching in the Mid-Infrared Spectrum

Abstract

In this work, we design a plasmonic metasurface as an optical refractive index sensor with high sensitivity and switching characteristics for the mid-infrared spectral region by employing organic material with reconfigurable attributes. This structure contains a cross element at the center which is surrounded by a frame with four similar rectangular parasitic elements at each corner. The parasitic elements as plasmonic absorbers are exploited for concentrating energy and reducing the reflection from the metasurface. This plasmonic absorber is utilized to improve the figure of merit (FOM) and sensitivity of the sensor because of the semi-Fano characteristic of the reflection response. Organic materials are being employed in this technique to design the absorber due to their distinct switching characteristics inside the gaps between the parasitic elements and cross frame which can be considered for controlling electric field distribution and reflection of the metasurface. The use of organic materials reduces the reflection of the metasurface about −11 dB in comparison to the primary model without organic material. In fact, the equivalent circuit and electric field can be highlighted to describe the features of this absorber and the DNA load effects. The switching ratio is obtained 42 times, and this absorber is modified for 110 THz with a reflection of −32 dB, and the FOM obtained for the sensor is 51 RIU⁻¹, with linear variation and sensitivity of 2440 nm/RIU.