Theoretical investigation of bidirectional and unidirectional dual-band absorption in one dimensional Octonacci sequences controlled by Dirac semimetal and Vanadium dioxide

The dual-band absorption properties of one-dimensional ternary Octonacci sequences, comprising dielectric, Dirac semimetal (DS), and Vanadium dioxide (VO2), are investigated theoretically and numerically using transfer matrix method, full-wave simulations, and impedance match theory. The photonic quasi-periodic multilayers exhibit bidirectional dual-band high absorption properties, attributed to strong electric field localization. Interestingly, this dual-band absorption can be spectrally tuned to the desired frequencies by adjusting the Fermi energy of the DS, changing the structure's parameters, the choice of dielectric, and the angle of incidence. Furthermore, the addition of a VO2 layer at the bottom of the Octonacci sequence enables the realization of dynamically tunable bidirectional and unidirectional dual-band absorption by modulating the conductivity of VO2. Remarkably, the absorption response remains insensitive to the polarization of the incident wave. These unique properties, together with the ease of manufacturing, make our proposed structures a promising candidate for wide applications in tunable optical devices.