THz near-field microscopes: Optimum operation conditions

We present the optimum operating conditions for THz scattering-type near-field microscopes using a self-consistent quasi-static line dipole image method. We show that the optimum incident angle of THz wave depends on the complex refractive index of substrate, and significantly enhance the near-field scattering signal. We also find that forward-scattering signal is preferred to back-scattering signal because the latter suffers from additional power loss due to a beam splitter.