Triple ultraviolet to visible perfect absorptions of lifted metamaterial for highly sensitive sensing and slow light

Achieving multiple perfect absorptions from ultraviolet (UV) to near-infrared (IR) region is practically important for metamaterial-based efficient harvesting of photons and biosensor. Here, we theoretically demonstrate a triple narrow and broad perfect absorptions (PAs) from visible to UV range in a lifted metamaterial made of aluminum vertical split-ring resonators (Al VSRR) on silica nanostrip /Al mirror. The three simultaneously achieved narrowband and broadband PAs with bandwidth of 283.3 nm, 8.9 nm and 18.2 nm are excited from magnetic plasmon resonance, surface plasmons polariton and plasmon standing wave mode, respectively, which is further explained by the impedance matching theory. The triple-band absorption peaks are further tailored by changing the size of the structure. The group index of the lifted Al VSRR array can reach as large as 2.5 × 10³ in the UV range. Moreover, due to the designed metamaterial being lifted with the reduced substrate effect, the figure of merit (FoM*) and sensitivity (S) in the UV range are as high as 1.1 × 10⁶ and 306 nm per refractive index unit‌ (306 nm/RIU), respectively. The proposed lifted metamaterial could have a considerable effect on the development of various UV plasmonic applications, including slow light nanodevices and optical sensor.