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Passive imaging cameras at sub-millimeter wavelengths are currently entering a new era with the development of large format arrays of direct detectors. Several of these arrays are being developed with bare absorbing meshes without any antenna coupling (lens or horn) structures. This paper uses a spectral electromagnetic model to analyze the performance of absorber based focal plane arrays in comparison...
We propose a novel method for establishing and aligning a THz ellipsometry system and for calibrating ellipsometry signals for precise THz ellipsometry measurements. The method significantly improves the THz ellipsometry accuracy compared to the current publications.
This paper presents a low-cost silicon-based terahertz computed tomography system for industrial volumetric imaging. The THz-CT scanner comprises a single radiator and detector at 490 GHz and a PTFE-lens based optical train that is fixed inside a portable cage system. It features a 2.5 mm resolution limited by the effective lens aperture and offers up to 62 dB SNR in chopped and 38 dB in a continuous-wave...
Illuminated by ultrashort optical pulses, large area multiplex terahertz semiconductor emitters that work on photo-Dember currents and Schottky potentials radiate a directional electromagnetic terahertz pulse which is controlled by the angular spectrum of the incident optical beam. Using the lens that focuses the incident near infra-red pulse, we have demonstrated THz emission focusing in free space...
The design, fabrication, and characterization of a terahertz transmission blazed-grating made out of paper tissue are presented. The angle dependent intensity observed in a spectroscopy setup is compared with the analytical results and electro-magnetic field scattering simulations. A close agreement between the measurements, simulations and analytical results illustrates the potential of this grating...
The properties of a machinable, high refractive index, low-loss, low-cost material are investigated. Both a THz-TDS and a Vector Network Analyzer (0.75–1.1 THz) are used to characterize the material and precisely obtain the absorption coefficient. Fresnel lenses are fabricated with a micro milling system to demonstrate the shaping capabilities of the aluminium nitride based ceramic.
A WR-3 waveguide band dynamic organic lens has been designed and its performance analysed using the CST Studio Suite software. In order to determine the dynamic behaviour of the lens, the patterned distribution of the electron-hole pairs in the photo-active region of the organic lens was input to the software, as a change in the complex permittivity. The dielectric response of the organic polymer...
The design and performance analysis are presented for a passive uncooled radiometer pixel suitable for integration in 28nm CMOS technology. In the configuration a single wideband antenna, operating from 200 GHz to 600 GHz, is connected to a pn-junction diode. Including the antenna-detector impedance mismatch, the detector shows an average NEP of 2.71 pW/√Hz such that, together with the antenna, the...
We present a nonuniform metasurface that operates as a flat lens at 400 GHz. Efficiency is enhanced by the use of a novel, tri-layer polarization-converting nonuniform meta-surface structure. The device is fabricated and experimentally characterized. The results confirm that the flat lens is indeed capable of focusing radiation to a focal spot with ∼68% efficiency. Constrained by spatial dispersion,...
We introduce a novel fast compressionless reconstruction algorithm for THz imaging. Based on Fourier imaging and a broadband THz spectrum, we demonstrate image reconstruction with high resolution using only 10s of pixels. First, we develop a mathematical framework based on polar Fourier optics and we demonstrate four cases where the fast reconstruction is possible. Second, we experimentally measure...
DESHIMA (Deep Spectroscopic High-redshift Mapper) is an instrument aiming at efficiently making spectroscopic redshift measurements of sub-mm wave galaxies (SMGs), thereby providing about the formation and the evolution of stars and galaxies. The aim of this work is to provide a preliminary study into the design of a wideband leaky lens antenna coupled quasi-optical system within a 1:3 bandwidth....
THz radiation can couple in various undesired ways to THz detectors, e.g. through wires or contact pads, aggravating calculation of sensible values for the device responsivity. We therefore investigate coupling of THz radiation to antenna-less large area field-effect transistors with dimensions in the range of the THz spot size proving that only a very small fraction of power is coupled through the...
In this paper a rigorous electromagnetic characterization of the setup for measuring the THz power radiated by pulsed photoconductive antenna is discussed. Such characterization is expressed in terms of efficiencies which quantify how much power is lost in the coupling between the various components involved in the measurement setup. The conducted analysis highlights how such efficiencies affect the...
We present the study of generation mechanism of terahertz (THz) radiation from tightly focused femtosecond laser pulses in a gas medium. The analysis of the experimental data led to the assumption that the dipole radiation prevails in most cases despite the existing conception regarding the dominating role of the quadrupole mechanism of radiation.
This contribution presents the design and sub-mm wave measurements of a wideband dual polarized leaky lens antenna coupled to kinetic inductance detector (KIDs) to be specifically used for tightly spaced focal plane arrays. The antenna is planar and composed by two crossed slots, fed by two orthogonal coplanar waveguide (CPW) lines. In transmission, the crossed CPW lines are fed differentially in...
Metasurfaces based on sub-wavelength patterning have major potential for arbitrary control of the wavefront of light by achieving local control of the phase, amplitude and polarization and allowing greater functionality and more compact devices. The resulting “flat” optical components hold promise to replace refractive and diffractive optics in a large number of applications ranging from camera modules...
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