Independently tunable dual-channel angle-sensitive narrow-band perfect absorber

In this correspondence, we introduce a versatile adjustable absorber featuring two distinct channels. Its primary composition includes strontium titanate (STO) and graphene. The refractive index of STO is influenced by temperature variations and the existence of the structural cavity, allowing for dynamic regulation of the absorption spectrum through external temperature changes and the angle of incident light. The developed device is capable of achieving dual-channel narrow-band perfect absorption at frequencies of 0.394 and 1.24 THz, demonstrating absorption rates of 99% and 98%, respectively. Importantly, we examined the Fermi level transition from 0 to 0.5 eV, revealing that the first resonance absorption peak can be adjusted within a range of 60% to 99%, accompanied by a redshift. This phenomenon is attributed to the local surface plasmon resonance induced by the graphene layer. The absorption characteristics of the second resonance remain relatively stable due to the peak formations within the Fabry-Perot cavity situated inside the STO layer. Given that the formant is influenced by temperature, it can be utilized as a temperature sensor. Furthermore, the absorptivity can be modified by altering the angle of the incident light. As a result of this angle dependence, optical switching can be achieved with a 22 dB ON/OFF ratio and a modulation depth close to 100%. Due to the symmetry of the absorption structure, the device remains unaffected by the polarization of the incoming light. The proposed tunable absorber has potential applications in electromagnetic absorption, optical switching, and various other domains.