Tunable ultra-broadband anisotropic absorbers based on multi-layer black phosphorus ribbons

We theoretically propose and numerically demonstrate a tunable ultra-broadband anisotropic absorber, which consists of a multi-layer BP/dielectric structure stacking on a gold mirror. The simulated results show that the proposed absorber can achieve nearly perfect absorption efficiency over the wavelength range from 16 to 28 μ m. Meanwhile, benefiting from the unique and versatile characteristics of BP materials, the absorption efficiency and absorption bandwidth can be actively controlled by either carrier doping or the geometrical parameters. These results may have great potential applications in designing anisotropic meta-devices with tunable spectral and polarization selectivity in the infrared and terahertz regimes.