Ultra-broadband mid-infrared absorption based on photonic topological transition and anti-reflection effect

We have developed and experimentally validated an ultra-broadband mid-infrared absorber comprising a periodic Ge/Cr multilayer structure coated with MgF₂ and ZnS films. Simulation studies demonstrate that the absorber’s performance remains robust across different polarizations and angles of incidence. The mechanism behind its ultra-broadband absorption capability stems from the synergistic effects of photonic topological transitions (PTT) and anti-reflection (AR) properties. Experimental results confirm that this absorber achieves an absorptivity exceeding 0.85 across a wide wavelength range from 2000 to 8410 nm. This innovative absorber not only broadens the scope of absorption bandwidths in the mid-infrared region but also holds significant promise for applications in thermal energy harvesting, thermal imaging, and radiation cooling.