Angular‐Dispersive Narrowband Absorption Induced by Quasi‐BIC in SiO2‐Au Metamaterial

Quasibound states in the continuum (BIC) have earned extensive attentions due to the capability to realize extremely high quality‐factor ( Q ‐factor) resonance. Here, a metamaterial composed of silicon dioxide (SiO 2 ) with low refractive index (≈1.45) on gold (Au) reflection mirror is proposed to realize narrowband perfect absorption with the assistance of quasi‐BIC and surface lattice resonance. The proposed SiO 2 ‐Au absorber based on SiO 2 metamaterial is composed of two tilted SiO 2 cubes into a unit cell and periodically arranged on Au reflection mirror. By optimizing the geometry parameters, the proposed absorber presents both accidental quasi‐BIC and symmetry‐protected quasi‐BIC modes with near‐perfect absorptivity and high Q ‐factor of 2330 and 1438, respectively. The Q ‐factor can be further improved to 10 4 by increasing the thickness of SiO 2 cubes to micrometer level. Meanwhile, the wavelength of absorption peak shows linear sensitivity of 16.67 and 17.88 nm per degree to incident angles as the absorptivity is higher than 92% and 75% in the spectra range of 215.0–141.0 nm, respectively. These results open the avenue for the metamaterial absorber in emitter, imaging, and biosensing applications.