This paper presents a terahertz (THz) metamaterial absorber made of stainless steel. We found that the absorption rate of electromagnetic waves reached 99.95% at 1.563 THz. Later, we analyzed the effect of structural parameter changes on absorption. Finally, we explored the application of the absorber in refractive index sensing. We numerically demonstrated that when the refractive index (n) is changing from 1 to 1.05, our absorber can yield a sensitivity of 74.18 μm/refractive index unit (RIU), and the quality factor (Q-factor) of this sensor is 36.35. Compared with metal–dielectric–metal sandwiched structure, the absorber designed in this paper is made of stainless steel materials with no sandwiched structure, which greatly simplifies the manufacturing process and reduces costs.
Enhancement of refractive index sensing for infrared plasmonic metamaterial absorber with nanogap