During this PhD thesis, two original microscopes combining an innovative contrast related to THz frequencies (from 0,1 to 10 THz) with the super-resolvent techniques of optical near field microscopy were built.Initially, we developed an instrument whose originality lies in the illumination method: a local IR/THz source generated in situ by optical rectification. Several metal and dielectric samples were imaged, illustrating the sub-wavelength resolution. Parallely, the mechanisms of image-formation in the microscope were investigated with a theoretical study.Subsequently, a modified version of the optical near field microscope working in an apertureless mode was designed and constructed. This configuration made it possible to reach a sub-micron resolution in the THz field, thanks to the addition of a metal tip serving as a scatterer for evanescent waves.
