Terahertz propagation properties of free-standing woven-steel-mesh metamaterials: Pass-bands and signatures of abnormal group velocities

We explore steel-mesh structures, which are commercially available as insets of chemical particle filters, in terms of their metamaterial properties below 1 THz, including both single- and multi-layer structures. Their pass-band characteristics are very similar to those reported for hole arrays in metal films, exhibiting power transmission as high as 88% for the lowest transmission band of single-layer structures. The transmission minima are explained in terms of the Rayleigh-Wood anomaly. The phase properties of the transmitted THz pulses reveal negative group delays of several picoseconds, i.e., abnormal group velocities, in spectral regions between pass-bands.