Terahertz Response of a Microfabricated Rod–Split-Ring-Resonator Electromagnetic Metamaterial

The first electromagnetic metamaterials (${\mathrm{E}\mathrm{M}}^3$) produced by microfabrication are reported. They are based on the rod–split-ring-resonator design as proposed by Pendry et al. [IEEE Trans. Microwave Theory Tech. 47, 2075 (1999)] and experimentally confirmed by Smith et al. [Phys. Rev. Lett. 84, 4184 (2000)] in the GHz frequency range. Numerical simulation and experimental results from far infrared (FIR) transmission spectroscopy support the conclusion that the microfabricated composite material is ${\mathrm{E}\mathrm{M}}^3$ in the range 1–2.7 THz. This extends the frequency range in which ${\mathrm{E}\mathrm{M}}^3$ are available by about 3 orders of magnitude well into the FIR, thereby widely opening up opportunities to verify the unusual physical implications on electromagnetic theory as well as to build novel electromagnetic and optical devices.

Figure 1

Geometric parameter definition of the RSR (left). Periodic arrangement of the RSR adopted for microfabrication (right).

Figure 2

Amplitude ratio of transmitted and incident waves as expressed by the parameters S21 (linear scale) in MWS for the rods, SRR and RSR.

Figure 3

Electroplated RSR structures of nickel with resist stripped off (left, scale bar $15\mu \mathrm{m}$) and gold embedded in resist AZP4620 (right, scale bar $20\mu \mathrm{m}$).

Figure 4

A bird's eye view (left) and a close-up (right) of $2.1\mathrm{m}\mathrm{m}\times 2.1\mathrm{m}\mathrm{m}$ microchips of Ni metamaterial embedded in a plastic (AZ P4620) matrix.

Figure 5

Measured spectral response of the two Ni RSR.

Figure 6

Measured spectral response of an Au RSR structure (Au sample 2, solid line) and its short-circuited version (dash-dotted line). The vertical lines indicate the wave numbers of the maximum as predicted by the numerical simulation (MWS) and the analytical formulas (Pendry).

Figure 7

Frequencies of the maxima of the spectral response curves versus the inner radius of the split-ring resonators for the measured (FTIR) and numerically simulated (MWS). The solid curve shows ${\nu }_0(r)$ of Eq. (1) for the Au cases. When the Ni case is scaled to the same $d$ as for Au it also comes close to the curve (●).

Figure 8

Spectrum with a resist slab only and without any sample.