Tunable mid-infrared ultra-narrowband plasmonic absorber and sensor based on bulk Dirac semimetal metamaterials

We propose a tunable mid-infrared ultra-narrowband plasmonic absorber and sensor based on bulk Dirac semimetal metamaterials, which is hypersensitive to the varation of background refractive index. Based on the tunable characteristic of bulk Dirac semimetal, the absorption wavelength can be dynamically adjusted without re-optimizing the geometric parameters, meanwhile, perfect absorption can be maintained despite the equal scale variation of the structure. The absorption bandwidth is so tiny that the sensitivity and figure of merit can be up to 16 000 nm RIU −1 and 3500 RIU −1 , respectively. Our results may open up new avenues for the design of optical filter and bio-chemical sensing.