Résumé
In the framework of a near-field remote sensing imaging experiment we developed an interferometric detection scheme at the open end of the rectangular waveguide that serves as probe. To proceed with lock-in detection, the Gunn source is further commutated at kHz frequencies. This results not only in an intensity sensitive image of the sample but also in a phase-contrast image that bring complementary informations. We relate this new image formation process to Gunn non-linearities occurring during the commutation process and plan to use it for near-field phase-sensing characterization at very low-cost.