Fig. 1

Schemes of (a) an oblique wire bundle (OWB) and (b) planar metamaterial absorbers. Measured and simulated absorption spectra of (c, d) oblique wire bundle (OWB) and (e, f) planar metamaterial absorbers under the x- and y-polarization incidences without PMMA. Insets show SEM images of the fabricated absorbers. It is worth pointing out that there appeared small peaks in the measured results at 70.5 THz for the spectra of the OWB metamaterial absorber, which could be attributed to the vibrational stretching mode of C = O. These peaks indicated the stronger field enhancement and larger hot spot areas, thus facilitating occurrence of Fano resonance from the OWB metamaterial absorber than the planar one. Note that the absorption dip in (c, d) might stem from the fluctuation of CO₂ concentration for the measurement of the background and the absorber.