@inproceedings{discovery10060151,
          volume = {10540},
         address = {Bellingham (WA), USA},
            note = {This version is the version of record. For information on re-use, please refer to the publisher's terms and conditions.},
       booktitle = {Proceedings of the Quantum Sensing and Nano Electronics and Photonics XV},
          editor = {M Razeghi and GJ Brown and JS Lewis and G Leo},
          series = {SPIE OPTO},
           month = {January},
       publisher = {SPIE},
            year = {2018},
           title = {Sub-wavelength near field imaging techniques at terahertz frequencies},
         journal = {QUANTUM SENSING AND NANO ELECTRONICS AND PHOTONICS XV},
        abstract = {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 {\ensuremath{\mu}}m. 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.},
            issn = {0277-786X},
          author = {Giordano, MC and Viti, L and Mitrofanov, O and Scamarcio, G and Mastel, S and Hillenbrand, R and Ercolani, D and Sorba, L and Vitiello, MS},
             url = {https://doi.org/10.1117/12.2291518},
        keywords = {Terahertz radiation, Near field, Near field optics, Quantum cascade lasers, Signal detection, Sensors, Spatial resolution}
}