Multi-resonant tunable absorber of terahertz metamaterial based on GaAs and VO2

Abstract

Based on the fact that the conductivity of photosensitive semiconductors can be regulated by external pump light, a metamaterial absorber with single-band and dual-band switchable in terahertz region is designed by replacing gallium arsenide (GaAs) within the nested cell ring structure. With the power increase of external pump light, the maximum absorptivity would be 99.9% when the conductivity of GaAs is setting as 5 × 105 S/m. Furthermore, based on the fact that the temperature can change the phase transition characteristic of vanadium oxide (VO2) and thus change the conductivity characteristic of VO2, the nested cell ring structure is extended, and a multi-resonant metamaterial absorber with tunable conductivity is proposed. When both GaAs and VO2 are in the metallic state, the absorption can be switched from triple-band to single-band, and when the conductivity of both is 5 × 105 S/m, the absorptivity is more than 99%. The GaAs is in the insulated state when there is no pump light irradiating and the conductivity of VO2 could be changed by temperature, or VO2 is in insulated state at room temperature and the conductivity of GaAs could be changed by pump light irradiation. After such supposed condition, the tunability from triple-band to dual-band shown in the proposed metamaterial absorber can be realized gradually. When the conductivity of VO2 or GaAs is 5 × 105 S/m, the maximum absorptivity of such multi-resonant tunable absorber is above 98%. Based on the controllability of GaAs and VO2 conductivity, the multi-resonant tunable absorber with arbitrary switching of single-band/dual-band/triple-band absorption state could be realized. At the same time, the designed absorber has excellent absorption characteristics about both transverse electric (TE) field and transverse magnetic (TM) one in the wide-angle incidence range, which is expected to be further applied in the research fields of modulator, frequency selector, detector, and so on.