%K Terahertz radiation, Near field, Near field optics, Quantum cascade lasers, Signal detection, Sensors, Spatial resolution %L discovery10060151 %V 10540 %C Bellingham (WA), USA %E M Razeghi %E GJ Brown %E JS Lewis %E G Leo %J QUANTUM SENSING AND NANO ELECTRONICS AND PHOTONICS XV %A MC Giordano %A L Viti %A O Mitrofanov %A G Scamarcio %A S Mastel %A R Hillenbrand %A D Ercolani %A L Sorba %A MS Vitiello %X Near-field imaging techniques at terahertz (THz) frequencies are severely restricted by diffraction. To date, different detection schemes have been developed, based either on sub-wavelength metallic apertures or on sharp metallic tips. However high-resolution THz imaging, so far, has been relying predominantly on detection techniques that require either an ultrafast laser or a cryogenically-cooled THz detector, at the expenses of a lack of sensitivity when high resolution levels are needed. Here, we demonstrate two novel near-field THz imaging techniques able to combine strongly sub-wavelength spatial resolution with highly sensitive amplitude and phase detection capability. The first technique exploits an interferometric optical setup based on a THz quantum cascade laser (QCL) and on a near-field probe nanodetector, operating at room temperature. By performing phase-sensitive imaging of THz intensity patterns we demonstrate the potential of our novel architecture for coherent imaging with sub-wavelength spatial resolution improved up to 17 μm. The second technique is a detector-less s-SNOM system, exploiting a THz QCL as source and detector simultaneously. This approach enables amplitude- and phase-sensitive imaging by self-mixing interferometry with spatial resolution of 60-70 nm. %D 2018 %O This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. %T Sub-wavelength near field imaging techniques at terahertz frequencies %B Proceedings of the Quantum Sensing and Nano Electronics and Photonics XV %I SPIE %S SPIE OPTO