Compact Dielectric Particles as a Building Block for Low-Loss Magnetic Metamaterials

We characterize experimentally a compact dielectric particle that can be used to design very low-loss artificial electromagnetic materials (metamaterials). Focusing on magnetic media, we show that the particle can behave almost identically to the well-known split-ring resonators (SRRs) widely used in present designs, without suffering from the Ohmic losses that can limit the applicability of SRRs especially at high frequencies. We experimentally compare qualitatively and quantitatively the dielectric particle with a typical split-ring resonator of the same size built on a low-loss dielectric substrate and show that at GHz frequencies the quality factor of the dielectric particle is more than 3 times bigger than that of its metallic counterpart. Low-loss and simple geometry are significant advantages compared to conventional metal SRRs.

Figure 1

(a) The electric field of the fundamental mode of a rectangular dielectric particle. (b) Picture of the dielectric particle (inset left), split-ring resonator (inset right), and the microstrip used to measure their properties. Notice the position of the dielectric particle with respect to the microstrip (shown for clarity at the edge of the waveguide) placed such that the magnetic field excites its fundamental mode. (c) The measured $S_{21}$ (solid) and $S_{11}$ (dashed) for the CDP (blue) and SRR (red lines).

Figure 2

(a) The retrieved real (solid) and imaginary (dashed) parts of the effective material parameters (top: permeability; bottom: permittivity) of the dielectric block (blue lines) and SRR (red lines). The small negative imaginary part of $\epsilon$ is an experimental artifact that does not show in numerical simulations (blue dotted line). (b) The measured normalized $|{\chi }_m^2|/{\omega }^4$ allows us to determine the quality factors of the two particles. We obtain $Q=509$ for the dielectric block (solid line), and $Q=141$ for the SRR (dashed line).

Figure 3

(a) Comparison between the effective permeability real (solid) and imaginary (dashed) components retrieved in a numerical simulation (red) and experimentally (blue) for the CDP-based medium; (b) Phase distribution of the electric field at 1.53 GHz in front, inside, and behind a NIM made of CDPs and vertical wires. Inset: top view of unit cell.