Superposition of ε -Near-Zero and Fabry-Perot Transmission Modes

Abstract

Metamaterials with near-zero permittivity exhibit extraordinary total transmission of waves within the length-independent conduit. However, such an \ensuremath{\epsilon}-near-zero (ENZ) transmission mode demonstrates an intrinsic narrow-band property using low-loss metastructures, e.g., extremely narrow waveguide transition at the cutoff frequency. As the counterpart to the ENZ mode, the Fabry-Perot (FP) mode also has near-zero reflection but depends on the channel length. For application considerations, the phenomenon of superpositioning ENZ and FP modes is analyzed theoretically and numerically to enhance the bandwidth of near-zero reflection within extreme mismatching waveguide transitions. The achieved bandwidth of the ENZ and FP mode cooperation is larger than the sum of two single modes, exhibiting feasible applications in the integrated waveguide structures, such as integrated transmission lines, circuits, and antennas. As an application example of this physical property, a waveguide crossover is proposed and experimentally verified to achieve wideband dual-narrow-channel total transmission within only one dielectric layer with an extremely low profile.