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Tunability of optical responses in black phosphorus-dielectric heterostructures and black phosphorus covered metallic grating at terahertz frequencies

Exceptional properties of the terahertz (THz) radiation lead to growing research on its potential applications in diverse areas. In this work, we study two structures to enhance the polarization selectivity and absorption of the black phosphorus (BP)-based polarizer and absorber at the THz regime. For the first structure, we use the transfer matrix approach to design and optimize optical absorption in a heterostructure comprising BP sandwiched within a linear dielectric media. We model the impact of structural and material parameters and incident wave characteristics on the performance of the designed absorber. In the second design, BP covered metallic grating, we use the equivalent circuit model to show the realization of high extinction ratio polarizer and perfect absorber. The proposed polarizer has a simple structure and a large extinction ratio of around 40 dB. The working frequency of the designed polarizer and absorber is tunable by changing the geometric size of the structure and the electron concentration in the BP layer. We verify the accuracy of our results using the full-wave simulations carried out by the Lumerical finite-difference time domain solution.