Quantitative coherent scattering spectra in apertureless terahertz pulse near-field microscopes

We present quantitative coherent measurements of scattering pulses and spectra in terahertz apertureless near-field microscopes. Broadband near-field image contrasts for both amplitude and phase spectra are measured directly from time-domain scattering signals with an unprecedentedly high single-scan signal-to-noise ratio (similar to 48 dB), with approach curves for both short (< 200 nm) and long (up to 82 mu m) ranges. By using the line dipole image method, we obtain quantitative broadband THz imaging contrasts with nanoscale resolution. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733475]