Tunable, large-scale and low-cost Si infrared absorbers

The aim to easily achieve large-scale perfect absorbers (PAs) with high-efficiency via a cost- effective fabrication process, has long been pursued. Herein, we experimentally demonstrate a tunable dual-band PA by a silicon film coupled plasmonic-colloidal crystal (CC) structure. The composite metallo-dielectric crystal can be fabricated in large scale (centimeter sized) using a colloidal self-assembled method and the standard film deposition technique. The measured absorption (A) for the dual-band spectrum is up to 97.9% (98.9%) in the near- infrared frequencies. Taking A above 90% into account, the spectral bandwidth values reach 211nm (111 nm) for the absorption bands at longer (shorter) wavelength ranges, respectively. Moreover, dual-band absorption with novel features of polarization-independent and incident angle-insensitive responses is observed for this absorber platform. These super absorption properties are mainly attributed to the excitation of the optical modes supported by the CC and their coupling interactions with the surface plasmon resonances of the metallic films. Furthermore, it is highly tunable for the achieved dual-band light absorption via tuning the geometry parameters of the silicon film. These structural features and optical behavior could lead to new avenues of manipulating light for low-cost and large-area optoelectronic applications.