Figure S2. Absorption spectra of AFF from visible (VIS) to NIR wavelength region (400 – 1000 nm) based on the FDTD method and measurement absorption. a) Incident light passes through glass substrate, top absorptive Cr film, intermediate insulator layer of PECVD SiO2, bottom reflective Cr, and air, in order. b) Absorption spectra at different SiO2 thicknesses from 80 nm to 120 nm at wavelength from 400 - 1000 nm region. A 90 nm in thickness of SiO2 exhibit broadband absorption over 0.93 from visible (VIS) to NIR wavelength region. c) The absorption of the upper Cr film is sensitive depending on the thickness compared to that of the lower film as a reflective metal due to its lossy nature. The peak absorption wavelength is blue-shifted as the bottom Cr layer thickness increases. d) Absorption spectra depending on a type of metal at VIS - NIR region. A Cr film has optically lossy and less dispersive characteristics, which can serve as bottom absorptive or top reflective layer. The interface reflection phase shifts become significantly different from 0 and π when a refractive index of top thin Cr film has comparable imaginary component (k) to real component (n) between 3.0 and 3.5 in the whole VIS-NIR region. e) Measured absorption spectra of AFF, 6 nm thin Cr film, and 90 nm thick Cr film, respectively, by using a spectrometer (SpectraPro ® 2300i, Princeton Instruments). The AFF absorbs incident light over 0.8 in whole VIS-NIR wavelength region, but Cr films mostly transmit or reflect the light, which exhibit less than 0.4 in the same wavelength region.