Vertical split-ring resonator perfect absorber metamaterial for IR frequencies realized via femtosecond direct laser writing

Perfect electromagnetic metamaterial absorbers based on three-dimensional (3D) vertical split-ring resonators for an infrared spectral range were fabricated using a combination of high-resolution direct laser write lithography and a simple metalization by sputtering. In accordance with theoretical predictions, the fabricated samples exhibit perfect absorption resonances tunable in the wavelength range of 4.5-9.2 mu m by changing the dimensions and spacing of the resonators. The structures exhibit polarization and incidence angle-invariant operation with absorbance in excess of 0.85 for incidence angles up to 30 degrees. In the future, they may find applications as narrow-band thermal emitters and for signal enhancement in mid-IR photodetectors. (C) 2017 The Japan Society of Applied Physics