Highly confined energy propagation in a gap waveguide composed of two coupled nanorod chains

We propose a subwavelength waveguide composed of two parallel nanorod chains. Based on the finite-difference time-domain analysis, we find that the electromagnetic energy can be highly confined in the gaps of nanorod pairs and transported in the gap waveguide through strong magnetic coupling interaction between neighboring nanorod pairs. In a structure with the rod length of 500 nm and the gap size of 100 nm, the energy flow cross section of the propagation mode can be restricted to the size of λ33×λ16 at the frequency of 130.0 THz. The corresponding attenuation length of energy propagation reaches 7.2λ. Moreover, these propagation modes exhibit a broad continuous frequency band from zero up to a cutoff frequency ωc ∼162.6 THz.