Ultrahigh-Sensitivity and Low-Thickness THz Refractive Index Sensor Based on Excitation of Tamm Plasmon Polaritons and Exploiting Fabry–Perot Resonances

In this article, an ultrahigh-sensitivity refractive index sensor based on the excitation of Tamm plasmon polaritons (TPPs) and Fabry-Perot resonances is presented. The sensor consists of a graphene sheet, a sample layer, and a 1-D dielectric-metallic photonic crystal (DM-PhC). The transfer matrix method (TMM) is used to evaluate the effects of various parameters, including the thickness of the layers and the component materials, as well as the chemical potential of graphene, on the absorption spectrum of the structure. The simulation findings show that the thickness and materials of the layers determine the number and frequency of resonances. The proposed structure can exhibit several absorption peaks of over 99% and even 100% in the frequency range of 0.5–3 THz. The sensitivity and figure-of-merit (FOM) values of the sensor are 1.58 THz/RIU and 42.7 RIU<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula>, respectively. As an innovation, utilizing a DM-PhC instead of an all- dielectric PhC (AD-PhC) improves the absorption behavior and decreases the total thickness of the sensor. The simplicity of fabrication, high tunability, low thickness, and ultrahigh sensitivity are the advantages of the proposed refractive index sensor. This sensor can be used in various industrial, biological, and biomedical applications.