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

• Triple narrowband and broadband PAs from the deep-UV to visible range are achieved, explained by impedance matching theory. • The group index (n g) of the lifted Al VSRR array for slow light can reach as large as 2.5 × 103 in the UV range. • Ultrasensitive biosensing in the UV region is achieved with FoM * of 1.1 × 106 at 312.5 nm. • Both the values of n g and FoM * are among the largest values in the UV range that have been recently reported. 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. [ABSTRACT FROM AUTHOR]