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Interdigitated photoconductive (IPC) switches are convenient sources and detectors for terahertz (THz) time domain spectroscopy. However, reflection of the emitted or detected radiation within the device substrate can lead to echoes that inherently limits the spectroscopic resolution achievable. In this work, we design and realize low-temperature-grown-GaAs (LT-GaAs) IPC switches for THz pulse generation...
We describe an approach to terahertz near field microscopy based on integrating custom-designed photoelectric radiation sources with near field probes on a single chip. Here we present results from new planar and conical probe designs.
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...
In this paper, a patch antenna designed to operate in a UHF passive radar with a broadband about 19% is validated in a real semi-urban scenario. Novel techniques, such as using air gap as substrate and E shaped patch, were considered in the fabrication. The proposed solution is used in the surveillance acquisition system of IDEPAR demonstrator, a DVB-T based passive radar system, to evaluate the detection...
We have measured the transmission spectra of splitring resonator metamaterials from 0 to 10 THz for parallel and perpendicular polarizations. Calculations of the lattice and plasmon mode dispersion relations in combination with electromagnetic simulations confirm the presence of multiple higher order lattice and plasmon modes. High frequency high-Q resonances that result from plasmon-lattice mode...
We report on large-area photoconductive THz emitters and detectors with an LT-GaAs active region fabricated on quartz substrates using a lift-off transfer process. These devices are compared to the same LT-GaAs emitters when fabricated on the growth substrate. We find that the transferred devices show higher optical-to-THz conversion efficiencies and significantly larger breakdown fields.
THz coplanar waveguides were fabricated on quartz wafers with integrated epitaxially transferred low temperature grown gallium arsenide photoconductive switches. THz radiation was excited on-chip and transmitted through a tapering of the coplanar waveguide structure where it was focused down to ∼ 1.66μm. Theoretical modelling of the device confirms high E-field confinement and concentration.
A physical mechanism is presented which can generate coherent and tunable terahertz (THz) radiation. Due to the dramatical lifting of SPPs energy, the dispersion can cross the light line, thus, the SPPs excited by an moving electron beam can be transformed into THz radiation. The radiation power density is enhanced nearly three orders, up to 105 W/cm2. The radiation frequency can be widely tuned by...
In this work, a typical two-dimensional (2D) material MoS2 on a dielectric substrate is measured by terahertz time-domain spectroscopy (THz-TDS) and analyzed using the Drude model. The transmittance and sheet conductivity of monolayer MoS2 have been obtained. This technology can be used to measure the thin film 2D materials in THz frequency regions.
This paper describes a method to improve the return loss, gain, and directivity of a planar antenna. Our approach is based on using electromagnetic band gap (EBG) structures within a dielectric substrate. We designed two type of antennas: a reference one — a standard patch antenna- and a patch antenna having an EBG substrate, both of them work at an operation frequency of 15 GHz. The reference antenna...
We present THz surface emission by difference frequency generation in nonlinear quantum cascade lasers operating at room temperature. The device comprises two separate, transversely superimposed gratings, one for selective feedback of the mid-infrared modes and one for surface emission of the generated THz radiation. The mid-infrared grating is realized as a higher order, loss-coupled distributed...
“super”-broadband materials and tools are surveyed which seamlessly work over all the near-infrared, mid-infrared and far-infrared regions, covering nearly three decades of wavelengths from 700 nm to 333 μm, or frequencies from 0.9 THz to 14,000 cm−1.
We design a T-shape structure reflecting mirror covered a gold thin film on the high-resistivity silicon substrate (ρ=1000 Ω·Cm) for the detector array. The electric field distribution of the T-shape structure is simulated by using finite difference time domain (FDTD) solutions in the frequency range from 300 GHz to 400 GHz. The electric field can be gathered in the central area of the silicon substrate...
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