26 January 2018 Sub-wavelength near field imaging techniques at terahertz frequencies
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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 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.
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Maria Caterina Giordano, Maria Caterina Giordano, Leonardo Viti, Leonardo Viti, Oleg Mitrofanov, Oleg Mitrofanov, Gaetano Scamarcio, Gaetano Scamarcio, Stefan Mastel, Stefan Mastel, Rainer Hillenbrand, Rainer Hillenbrand, Daniele Ercolani, Daniele Ercolani, Lucia Sorba, Lucia Sorba, Miriam S. Vitiello, Miriam S. Vitiello, } "Sub-wavelength near field imaging techniques at terahertz frequencies", Proc. SPIE 10540, Quantum Sensing and Nano Electronics and Photonics XV, 105400N (26 January 2018); doi: 10.1117/12.2291518; https://doi.org/10.1117/12.2291518
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