Ultrathin metamaterial-based perfect absorbers for VHF and THz bands

• We investigated an ultrathin and angularly-stable metamaterial perfect absorber (MPA) for VHF and THz bands.
• Our MPA works well for a wide range of incident angle of electromagnetic wave and polarization-independent behavior.
• By integrating a ferroelectric material (strontium titanate), a thermo-tunable MPA is realized in the THz region.
• Our results presents good candidates for potential devices operating from the radio to the THz range.

An ultrathin and angularly stable metamaterial perfect absorber (MPA) is demonstrated for VHF-band using four connected split-square resonators structure and low-cost fabrication process. The total incoming energy of electromagnetic wave (at 250 MHz) is consumed inside the efficient thickness, which is 240 times smaller than the absorption wavelength of MPA. Our MPA works well for a very wide range of incident angle up to 45° of electromagnetic wave and exhibits the polarization-independent behavior. Furthermore, by scaling the initial design and integrating a ferroelectric material (strontium titanate), a thermo-tunable ultrathin MPA is realized in the THz region. At room temperature (300 K), the thickness of THz MPA reaches roundly 1/300 of the working wavelength. In addition, a fractional frequency shift of 49% at the absorption over 90% can be controlled in the varied temperature range from 150 to 400 K. Our results presents good candidates for potential devices operating from the radio to the THz range.