912 research outputs found
Phase-sensitive terahertz imaging using room-temperature near-field nanodetectors
Imaging applications in the terahertz (THz) frequency range are severely restricted by diffraction. Near-field scanning probe microscopy is commonly employed to enable mapping of the THz electromagnetic fields with sub-wavelength spatial resolution, allowing intriguing scientific phenomena to be explored, such as charge carrier dynamics in nanostructures and THz plasmon-polaritons in novel 2D materials and devices. High-resolution THz imaging, so far, has relied predominantly on THz detection techniques that require either an ultrafast laser or a cryogenically cooled THz detector. Here, we demonstrate coherent near-field imaging in the THz frequency range using a room-temperature nanodetector embedded in the aperture of a near-field probe, and an interferometric optical setup driven by a THz quantum cascade laser. By performing phase-sensitive imaging of strongly confined THz fields created by plasmonic focusing, we demonstrate the potential of our novel architecture for high-sensitivity coherent THz imaging with sub-wavelength spatial resolution. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen
Cooling many particles at once
Published versio
High performance bilayer-graphene Terahertz detectors
We report bilayer-graphene field effect transistors operating as THz
broadband photodetectors based on plasma-waves excitation. By employing
wide-gate geometries or buried gate configurations, we achieve a responsivity
and a noise equivalent power in the 0.29-0.38 THz range, in photovoltage and photocurrent mode.
The potential of this technology for scalability to higher frequencies and the
development of flexible devices makes our approach competitive for a future
generation of THz detection systems.Comment: 8 pages, 5 figures. Submitted to Applied Physics Letter
Terahertz near-field nanoscopy based on detectorless laser feedback interferometry under different feedback regimes
Near-field imaging techniques, at terahertz frequencies (1-10 THz), conventionally rely on bulky laser sources and detectors. Here, we employ a semiconductor heterostructure laser as a THz source and, simultaneously, as a phase-sensitive detector, exploiting optical feedback interferometry combined with scattering near-field nanoscopy. We analyze the amplitude and phase sensitivity of the proposed technique as a function of the laser driving current and of the feedback attenuation, discussing the operational conditions ideal to optimize the nano-imaging contrast and the phase sensitivity. As a targeted nanomaterial, we exploit a thin (39 nm) flake of Bi2Te2.2Se0.8, a topological insulator having infrared active optical phonon modes. The self-mixing interference fringes are analyzed within the Lang-Kobayashi formalism to rationalize the observed variations as a function of Acket’s parameter C in the full range of weak feedback (C < 1)
DNA waves and water
Some bacterial and viral DNA sequences have been found to induce low
frequency electromagnetic waves in high aqueous dilutions. This phenomenon
appears to be triggered by the ambient electromagnetic background of very low
frequency. We discuss this phenomenon in the framework of quantum field theory.
A scheme able to account for the observations is proposed. The reported
phenomenon could allow to develop highly sensitive detection systems for
chronic bacterial and viral infections.Comment: Invited talk at the DICE2010 Conference, Castiglioncello, Italy
September 201
Near-field terahertz probes with room-temperature nanodetectors for subwavelength resolution imaging
Near-field imaging with terahertz (THz) waves is emerging as a powerful technique for fundamental research in photonics and across physical and life sciences. Spatial resolution beyond the diffraction limit can be achieved by collecting THz waves from an object through a small aperture placed in the near-field. However, light transmission through a sub-wavelength size aperture is fundamentally limited by the wave nature of light. Here, we conceive a novel architecture that exploits inherently strong evanescent THz field arising within the aperture to mitigate the problem of vanishing transmission. The sub-wavelength aperture is originally coupled to asymmetric electrodes, which activate the thermo-electric THz detection mechanism in a transistor channel made of flakes of blackphosphorus or InAs nanowires. The proposed novel THz near-field probes enable room-temperature sub-wavelength resolution coherent imaging with a 3.4 THz quantum cascade laser, paving the way to compact and versatile THz imaging systems and promising to bridge the gap in spatial resolution from the nanoscale to the diffraction limit
The role of the electromagnetic field in the formation of domains in the process of symmetry breaking phase transitions
In the framework of quantum field theory we discuss the emergence of a phase
locking among the electromagnetic modes and the matter components on an
extended space-time region. We discuss the formation of extended domains
exhibiting in their fundamental states non-vanishing order parameters, whose
existence is not included in the Lagrangian. Our discussion is motivated by the
interest in the study of the general problem of the stability of mesoscopic and
macroscopic complex systems arising from fluctuating quantum components in
connection with the problem of defect formation during the process of
non-equilibrium symmetry breaking phase transitions characterized by an order
parameter.Comment: Physical Review A, in the pres
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