THz imaging in the near-field

A time-domain terahertz spectroscopy (THz-TDS) is extended to real time `T-ray' imaging by reducing the acquisition time of THz waveforms by four orders of magnitude. Because of the long wavelength of magnitude of the THz radiation, the spatial resolution of this essentially diffraction-limited imaging system is several hundred micrometers and frequency dependent over the large bandwidth of the THz pulses. However, the sub-wavelength spatial resolution can be achieved by passing radiation through the a small aperture, so that the spatial resolution is determined by the size of the aperture rather than the wavelength of the radiation.