Abstract
We experimentally demonstrate a CMOS compatible medium wave infrared metal-insulator-metal (MIM) metamaterial absorber structure where for a single dielectric spacer thickness at least 93% absorption is attained for 10 separate bands centred at 3.08, 3.30, 3.53, 3.78, 4.14, 4.40, 4.72, 4.94, 5.33, 5.60 μm. Previous hyperspectral MIM metamaterial absorber designs required that the thickness of the dielectric spacer layer be adjusted in order to attain selective unity absorption across the band of interest thereby increasing complexity and cost. We show that the absorption characteristics of the hyperspectral metamaterial structures are polarization insensitive and invariant for oblique incident angles up to 25° making them suitable for practical implementation in an imaging system. Finally, we also reveal that under TM illumination and at certain oblique incident angles there is an extremely narrowband Fano resonance (Q > 50) between the MIM absorber mode and the surface plasmon polariton mode that could have applications in hazardous/toxic gas identification and biosensing.
Highlights
Medium wave infrared (MWIR) radiation, defined as the region between 3 and 5 μm of the electromagnetic spectrum, has several important characteristics
We study experimentally and via simulations the absorption characteristics for both normally incident radiation and obliquely incident radiation of 40 MWIR metamaterial absorbers where the electric ring resonator (ERR) arm length and dielectric thickness are varied
In summary we have experimentally detailed and described a CMOS compatible metalinsulator-metal metamaterial absorber geometry where for a single SiO2 spacer thickness of 100 nm a minimum of 93% absorption is attained for 10 separate bands centred at 3.08, 3.30, 3.53, 3.78, 4.14, 4.40, 4.72, 4.94, 5.33, 5.60 μm throughout the MWIR spectrum
Summary
Medium wave infrared (MWIR) radiation, defined as the region between 3 and 5 μm of the electromagnetic spectrum, has several important characteristics. We study experimentally and via simulations the absorption characteristics for both normally incident radiation and obliquely incident radiation of 40 MWIR metamaterial absorbers where the ERR arm length and dielectric thickness are varied. The experimental spectral responses show similar trends to those simulated; the peak absorption wavelength position red shifts with increasing cross-arm length and the absorption magnitude is strongly dependent on the SiO2 thickness. The peak absorption wavelength positions for the 100 nm thick SiO2 metamaterial absorbers are 3.08, 3.30, 3.53, 3.78, 4.14, 4.40, 4.72, 4.94, 5.33, 5.60 μm This is, to the best of our knowledge, the first experimental demonstration of a spectrally selective metamaterial absorber that has greater than 90% absorption magnitude across the entire MWIR region for a single dielectric spacer layer thickness. Our experimental Q values are typical of single band cross shaped ERR MIM metamaterial absorbers
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