Strong optical activity in metamaterials of metallic screw arrays

Strong optical activity is created by metamaterials of metal screw hole arrays and metal male screw arrays. At some resonant frequencies, polarization states of linearly-polarized incident electromagnetic waves become elliptic and rotate after passing through these metamaterials. We have measured the polarization characteristics of terahertz waves transmitted through the metal screw hole arrays and metal male screw arrays with various structural parameters. The polarization change for the metal screw hole arrays are almost same as that for a single metal screw hole. The resonant frequency is independent of the thickness of the samples. These results indicate that the origin of the polarization change in the metal screw hole arrays is attributed to the screw pitch resonance.