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Reliable doping in semiconductor nanowires is essential for the development of novel optoelectronic devices. Dopant incorporation within the nanowire can allow for optimisation of key optoelectronic properties, such as electron mobility and carrier lifetime. Thus, in-depth characterisation of doping mechanisms in semiconductor nanowires and their effect on the nanowire optoelectronics properties is...
We present the optimum operating conditions for THz scattering-type near-field microscopes using a self-consistent quasi-static line dipole image method. We show that the optimum incident angle of THz wave depends on the complex refractive index of substrate, and significantly enhance the near-field scattering signal. We also find that forward-scattering signal is preferred to back-scattering signal...
We have experimentally investigated electronical excitation of Fano resonances in subwavelength slits. These resonances can provide strong concentration of electromagnetic waves under subwavelength conditions in microwave and terahertz regime as analogous to plasmonic Fano resonances in optics regime. It is observed that the quality factors of the resonances become exceedingly high by introducing...
We theoretically and experimentally study the scattering of p-polarized EM waves from 1D arrays of thin metal plates at THz frequencies. In the simulation results, the reflectance is normally small but extraordinarily high under certain conditions. The resonant conditions correspond to coupled excitations between the surface modes along the array and the cavity modes inside the parallel-plate waveguides...
The interaction of a slow-wave in a corrugated dielectric waveguide with drifting electron gas in a semiconductor with the multi-valleys conduction band is studied in the linear model. Contribution of each valley into the net loss/amplification is investigated. Substantial amplification is possible in large fields due to slow-wave interaction with carriers in satellite valleys.
Brownout refers to dust cloud created by the rotor downwash of a helicopter. When it occurs, the visibility becomes limited, or even null. The pilot can be desorientated and accident may happen. No existing imaging systems can see through dust clouds, in real-time and with sufficient resolution. Using waves between 100GHz and 1THz seems to be a good solution to make a compact and suitable imaging...
Semiconductors and metals respond to strong electric fields in a highly nonlinear fashion. Using single-cycle THz field transients it is possible to investigate this response in regimes not accessible by transport-based measurements. Extremely high fields can be applied without material damage, intrinsic, undoped materials can be studied, and field-induced electron emission into free space can be...
The possibility of generation of high-power (multi-megawatt) broadband terahertz radiation during stimulated backscattering of an intense millimeter-wavelength pump wave by a high-current reletivistic electron beam (REB) is shown. With allowance for a significant parameter spread that is typical for high-current REBs, the kinetic interaction regime is expedient, This regime leads to the broadening...
A 300 GHz pulse gyrotron has been developed for collective Thomson scattering diagnostics in the Large Helical Device with a careful design consideration. Single-mode oscillation of more than 320 kW was attained. The frequency spectrum was very narrow and stable across the pulse width up to 80 μs. No parasitic mode was observed during the whole pulse width including the turn-on and turn-off phases...
We propose and demonstrate a novel near-field probe, resonant at terahertz (THz) frequencies. A conical metal tip, with length 50–1000 μm is fabricated directly to the surface of a semiconductor surface, acting as a radially-polarized THz source. High field confinement is seen at the apex of the probe. The scattering efficiency is frequency dependent, and is likely related to the dipolar resonance...
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