Polarization contrast terahertz-near-field imaging of anisotropic conductors

The authors have developed a near-field spectrometer operating in the terahertz range between 30THz and 1.4THz, which consists of backward-wave oscillators as continuous-wave sources and a photoinduced aperture as near-field probe. The instrument provides the possibility of terahertz spectroscopy and imaging with subwavelength resolution utilizing an adjustable aperture, but without a complicated probe-sample distance control. Due to the strongly polarized radiation, anisotropic sample properties can be investigated on spot sizes much smaller than the wavelength. The performance is demonstrated on subwavelength sized crystals of the quasi-one-dimensional organic conductor (TMTTF)2PF6.