Dynamically Tunable Plasmon-induced Transparency in Parallel Black Phosphorus Nanoribbons

In this paper, we investigate the dynamically tunable plasmon-induced transparency (PIT) effects in parallel black phosphorus nanoribbons (BPNRs). The results show that the BPNRs having different lengths can be regarded as bright modes. Single-band, double-band, triple-band, and multi-band PIT effects based on the bright-bright mode coupling between parallel BPNRs are achieved. The physical mechanism of the single-band model can be explained theoretically by the radiating two-oscillator (RTO) model. Due to the heavier effective mass in the zigzag (ZZ) direction of the BP, the frequencies of the transparent peaks are shifted to lower frequencies when the placement directions of BPNRs are changed from the X-direction to the Y-direction. Furthermore, the resonant frequencies of the transparent windows in each model can be tuned by changing the relaxation rates of the BPNRs. The frequencies of the transparent windows are blue-shifted as the relaxation rates are increased. Finally, The corresponding sensors based on single-band PIT effect show high sensitivities of 7.35 THz/RIU. Our study has potential applications for improving the design of multiple-band filters, sensors and on-off switcher.