A polarization-dependent perfect absorber with high Q -factors enabled by Tamm phonon polaritons in hyperbolic materials.

As a natural biaxial hyperbolic material, α-phase molybdenum trioxide (α-MoO 3 ) is highly anisotropic, making it an ideal candidate for polarization-dependent devices. Herein, using a Tamm configuration where one-dimensional photonic crystal is coated on an α-MoO 3 substrate separated by a dielectric interlayer, we demonstrate the perfect absorption effect in the mid-infrared band governed by Tamm phonon polaritons. The resultant absorption peak exhibits an ultra-narrow bandwidth due to the polaritonic resonance with a high quality factor of up to 181. By varying the thickness of the interlayer, we demonstrate that near-unity absorption resonances can be tuned to a wider range of wavelengths. In addition, due to the in-plane anisotropy of α-MoO 3 , the device exhibits an outstanding polarization-dependent absorption performance, rendering it highly useful for various applications. Also, we show that the electronic tunability of the device is through addition of a graphene monolayer. These excellent results suggest that the designed structure could be promising in applications such as infrared absorbers, polarization detectors, sensors and energy harvesting devices.