A numerical analysis of a highly sensitive hexagonal plasmonic refractive index sensor

The article proposes and quantitatively investigates the performance characteristics of a surface plasmon polariton based refractive index sensor with metal-insulator-metal arrangement, which demonstrates higher sensitivity than many recent studies. The Finite Element Method (FEM) has been used to quantitatively analyze the refractive index sensor's transmission properties and sensitivity in various configurations. The structure consists of two symmetrical triangular stubs coupled to a ring-type hexagonal resonator with two slits in opposing arms. The highest sensitivity and FOM observed is 4571.7 nm/RIU and 63.3, respectively. It has a sensing resolution of 2.18 x 10-7 RIU. Mode 1 has a maximum figure of merit and quality factor of 197.6 and 204.15, respectively. The high quality factor of mode 1 indicates that this sensor is suitable for use as a notch filter. The sensor has been evaluated for temperature sensing, and the temperature sensitivity is significantly higher than that of recent studies. Some sensors claim to be highly sensitive, but they often use a high refractive index region to evaluate the sensor, which is misleading because the sensitivity would be higher in the region with a high refractive index. The effect of adding the two slits in opposing arms is that the figure of merit can be increased by increasing the width of the two slits. Refractive index sensors are useful in medical diagnostics and have a wide variety of applications. The combination of very high sensitivity and FOM in a tiny and compact configuration is ideal for on-chip plasmonic nanosensors.