Optical Refractive Index Sensors Based on Plasmon-Induced Transparency phenomenon in a Plasmonic Waveguide Coupled to Stub and Nano-disk Resonators

Plasmon-induced transparency (PIT) in the transparent window provides new insights into the design of optical devices such as optical sensors. Therefore, in this paper, four novel structures based on the PIT phenomenon are proposed to design plasmonic refractive index sensors (RISs). The designed structures consist of metal-insulator-metal (MIM) waveguides, stub resonators (SR), and nano-disk resonators (NDRs) containing metal strips (MSs). By using an MIM waveguide, an SR, and an NDR containing MSs, the first RIS (main RIS) is designed and simulated using the finite difference time domain (FDTD) method. To verify FDTD simulations, the stub-coupled MIM waveguide system which is used to design the main RIS is analyzed using the transmission line method (TLM). The maximum sensitivity and FOM of the main RIS obtain 725.1 nm/RIU and 91.78 RIU-1, respectively. By coupling two SRs, two NDRs containing MSs, and two SRs and NDRs containing MSs simultaneously, the other three RIS structures are designed. Increasing Q factors of the designed RISs results in higher FOM values for these new structures. The maximum FOM values for RIS I, RIS II, and RIS III are achieved at 120.18, 144.27, and 113.07 RIU-1, respectively.

Automated summary

This paper proposes four novel structures based on plasmon-induced transparency (PIT) for designing plasmonic refractive index sensors (RISs). The performance of these structures is simulated and validated using the finite difference time domain (FDTD) method. The main RIS achieves a maximum sensitivity of 725.1 nm/RIU and a figure of merit (FOM) of 91.78 RIU-1. By enhancing the design, higher FOM values are achieved for the other three RIS structures, with RIS I, RIS II, and RIS III reaching maximum FOM values of 120.18, 144.27, and 113.07 RIU-1, respectively.