Large-area, low-cost, ultra-broadband, infrared perfect absorbers by coupled plasmonic-photonic micro-cavities

Perfect absorption of electromagnetic wave is emerging as a promising technology for its potential applications in harvesting solar energy, infrared detection and photovoltaic devices. Recent studies have reported a variety of plasmonic or meta-material structures, which are designed and fabricated to provide broadband absorption by utilizing multiple resonators in a composite unit cell. Coupled plasmonic-photonic micro-cavities, formed by using the colloidal crystal that does not have closed packed structure as the structural template, are surprisingly found to be efficient infrared absorption devices in an ultra-broadband frequency range. Taking the absorptivity above 0.9 into account, the operation bandwidth is up to 2.851 μm in the infrared range. The excellent absorption capability can be attributed to the cooperation effects of the plasmonic resonances by the metal caps and the photonic modes by the colloids. The absorber exhibits polarization-independent and wide-angle behaviors. These findings not only reveal the advantages of colloidal crystals as low-cost materials for ultra-broadband absorbers, but also provide inspiration for future development of high-performance, large-area infrared optoelectronic devices.