Light manipulation in sub wavelength geometries is an attribute that nano photonics offers. Propagation and guiding, beaming, and confinement of the light are the most studied concepts in this area. Design of an ideal “black body” absorber with absorption of unity is one of the ultimate goals in the field of sub wavelength light confinement. Up to now, several methods and architectures are exploited to obtain high performance black absorber. One of the most commonly used approaches is to utilize metal-insulator (MI) multilayer stack. It was theoretically demonstrated that the use of periodic MI pairs can provide impedance matching in a broad frequency range . Later, It was theoretically and experimentally proved that Cr-SiO2 multilayer can provide highest light absorption over 90% in a broad wavelength range between 400 nm-1400 nm .
In this paper, we demonstrate a facile, lithography free, and large scale compatible fabrication route to fabricate ultra-broadband wide angle perfect absorber based on metal-insulator-metal-insulator (MIMI) stack design. 600 nm bandwidth (400 nm – 1000 nm) is attained utilizing this planar design. This design is later improved by intro-duction of non-uniform texturing  and employing disordered nano hole plasmonic patterns where the overall process is large scale compatible and lithography free. Our findings show that the optimized design can retain light absorption above 0.9 over a wide range wavelength of 400 nm – 1490 nm, as shown in Fig. 1. To the best of our knowledge, this bandwidth is the highest among other reported studies that employ this multilayer architec-ture.
Fig. 1: The measured absorption spectra for a) planar, b) non-uniform texturing, and c) nanohole plasmonic cases.
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Amir Ghobadi, Bayram Bütün, and Ekmel Özbay, "Metal-insulator-metal multilayer-based ultra-broadband perfect absorbers: from non-uniform texturing to nano-hole plasmonic units (Conference Presentation)," Proc. SPIE 10528, Optical Components and Materials XV, 105281F (Presented at SPIE OPTO: February 01, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2291469.5751438513001.
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