Perfect light absorption (PLA) in nanophotonics has a wide range of applications from solar-thermal based applications to radiative cooling. However, most of the proposed platforms require intense lithography which makes them of minor practical relevance. On the other hand, thin-film light absorbers are lithographically free and can be deposited cheaply on large area based on matured technologies. However, thin-film light absorbers were thought to have major limitation and cannot be tailored compared to metamaterials. Here, we show how to design PLA using thin-films in terms of wavelength range, bandwidth, spatial profile of optical losses, directionality and iridescence. We also show that iridescent free, PLA can occur by simply heating metallic thin-films when the metal is of low reflectance and its oxide is of high refractive index. We theoretically and experimentally demonstrate Generalized Brewster angle effect in thin film light absorbers. In addition, we demonstrate hydrogen sensing using three different PLA strategies showing record sensitivity and figure of merit. Furthermore, we show various strategies to create ultra-pure structural colors. Finally, we demonstrate different solar-thermal applications for novel thin-film PLA designs.

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Mohamed El Kabbash, Theodor Letsou, Michael R. Hinczewski, Giuseppe r Strangi, and Chunlei Guo, "Designer thin-film based perfect light absorption and its applications in structural coloring, gas sensing, and solar-thermal conversion (Conference Presentation)," Proc. SPIE 11089, Nanoengineering: Fabrication, Properties, Optics, Thin Films, and Devices XVI, 1108904 (Presented at SPIE Nanoscience + Engineering: August 11, 2019; Published: 10 September 2019); https://doi.org/10.1117/12.2528370.6083793032001.