Hybrid superconductor/semiconductor devices constitute a powerful platform to investigate the emergence of new topological state of matter. Among all possible semiconductor materials, InAs represents a promising choice, owing to its high quality, large g-factor and spin–orbit component. Here, we report on InAs-based devices both in one–dimensional and two–dimensional configurations. In the former, low-temperature measurements on a suspended nanowire are presented, inspecting the intrinsic spin–orbit contribution of the system. In the latter, Josephson Junctions between two Nb contacts comprising an InAs quantum well are investigated. Supercurrent flow is reported, with Nb critical temperature up to Tc ∼ 8 K. Multiple Andreev reflection signals are observed in the dissipative regime. In both systems, we show that the presence of external gates represents a useful knob, allowing for wide tunability and control of device properties, such as spin–orbit coherence length or supercurrent amplitude.
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.