Large-Area Low-Cost Tunable Plasmonic Perfect Absorber in the Near Infrared by Colloidal Etching Lithography

Optical elements with absorbance close to unity are of crucial importance for diverse applications, ranging from thermal imaging to sensitive trace gas detection. A key factor for the performance of such devices is the need for absorbance with high acceptance angles, which are able to utilize all incident radiation from the forward-facing half-space. Here, a tunable, angle-, and polarization independent large-area perfect absorber is reported, which is fabricated by a combination of colloidal lithography and dry-etching. This design is easy and fast to produce, and low-cost compared with other common methods. Variation of the dry-etching time shifts the resonance from almost 825 to 1025 nm with reflection smaller than 3% and zero transmission. Due to the inherent disordered arrangement, this design is fully polarization independent and the absorbance remains higher than 98% for incident angles up to 50 degrees.