Metamaterial-Based Low-Conductivity Alloy Perfect Absorber

We propose a simple way to enormously broaden the bandwidth of the metamaterial absorber formed by a low-conductivity square alloy patch and a dielectric layer on top of an alloy ground plane. The FWHM of the device can be up to 38.8%, which is 3.6 times larger than that of the high-conductivity (Au) absorber. Moreover, we demonstrate an ultra-broadband and polarization insensitive absorber by simply stacking three different-sized square alloy patches. Greater than 90% absorption is obtained across a frequency range of 1.34 THz with the central frequency around 1.90 THz. The relative absorption bandwidth of the device is greatly improved to 70.4%, which is much larger than previous results. The mechanism for the ultra-broadband absorption is attributed to the overlapping of four different but closely positioned resonance frequencies. The results of the proposed alloy metamaterial absorber appear to be very promising for solar cells, detection, and imaging applications.