This paper demonstrates broadband THZ near-field measurements performed on different types of antennas and meta materials structures, all having sub-wavelength dimensions. The time and frequency dependence of the electric near-field are presented and compared with numerical calculations. Using terahertz time-domain spectroscopy (THz-TDS), the electric near-field components Ex(t), Ey(t) and Ez(t) in the vicinity of antenna structures for wave vectors k corresponding to kaLt1, kaap1 and ka >1, where a is the typical dimension of the structure. The measurements reveal how the extremity of the wire generates propagating fields resembling a Sommerfeld wave on a cylindrical wire.

Sub-wavelength, metallic circular aperture arrays were studied in the near-field at terahertz frequencies, using terahertz time-domain spectroscopy (THz-TDS). Two different periodicities were investigated and array subsections were imaged in both the time- and frequency-domain.