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For terahertz microscopy, we propose an original approach with Planar Goubau Lines (PGL) by taking advantage of the confinement around the metallic strip. The idea is to obtain an alternative to the illumination by free space wave. The structure is fabricated on a thin high resistivity silicon substrate and it is composed of two CPW-PGL transitions, two bendings and a coupling region between the two...
High fill-factor, high extinction ratio THz polarizers have been fabricated with anti-reflection coatings to reduce insertion loss at target frequencies. The anti-reflection coating is made from inexpensive PVC and easy to apply using a hotplate. This coating technique has improved the transmission of perpendicularly polarized signal through the polarizer by ∼2 dB, resulting in transmission through...
Fabry-Perot resonances in planar terahertz metamaterial structures have been investigated both theoretically and experimentally. It has been demonstrated that performance of frequency-agile metamaterial modulator can be optimized by adjustment of dielectric substrate thickness in accordance with operating frequency of metamaterial.
The polarization response of THz wavelength metamaterials modulators have been researched, and a special modulator structure has been proposed, simulated and fabricated. Compared with the traditional split ring resonator modulators which are all polarization sensitive, the new structure has properties of polarization insensitive. The structure is a completely symmetrical metal structure and has the...
This article describes a semi-coaxial through glass via(TGV) interposer structure for high frequency three dimensional(3D) system applications. In order to overcome impedance mismatch in high frequency transition, a semi-coaxial structure is designed. The glass is 200 μm thick and the via's diameter is 50 μm. Re-distribution layer (RDL) line to TGV transition structure is designed and simulated to...
We demonstrate a technique of fabricating freestanding all-metal two-dimensional (2D) and three-dimensional (3D) terahertz metamaterials through injection molding of gallium, a metal that melts at temperatures slightly above room temperature. To obtain free-standing metamaterials, two polydimethylsiloxance (PDMS) molds are created using conventional soft lithography, reversibly bonded through van...
We present an approach for two-port on-wafer calibration to establish the test reference planes within the substrate of the device under test for the WR3 (220–325 GHz) and WR5 (140–220 GHz) frequency bands. On-wafer calibration is useful for characterizing elements such as transistors for modeling or for the confirmation of circuit models. There are numerous publications for on-wafer calibrations,...
Approaches based on thinning down the substrate under the antenna are often used in order to increase efficiency of detectors built with MOSFETs and antennae printed on thick substrates. Such detectors have relatively low responsivity. In applications where cheap individual pixels are required, standard silicon lenses used to increase the responsivity are prohibitively expensive. In this paper an...
This paper shows simulated and measured results of ultra-low cost metal mesh filters on electrically thick substrates for millimeter-wave and THz bands. It provides a broad overview of metal mesh filters currently available and suggest why it is worth moving to an electrically thick substrate for ultra-low cost applications. We demonstrate scalable traditional metal mesh filters on 525 µm thick fused...
To improve the coupling efficiency of Quantum Well Infrared Photo-detector (QWIP), a new grating was proposed. By optimizing the grating, it can work in 3∼5µm and realize an enhanced peak at 4.5µm. With the uniform result of simulation and experiment, an optimizing metallic grating was designed.
Recent simulation and experimental work has resulted in the realization of low-cost, substrate-based, THz wire-grid polarizers fabricated on crystalline-quartz substrates that exhibit both high extinction ratios and low insertion losses. The broad bandwidth performance of these high fill-factor wire-grid polarizers are characterized using terahertz time-domain spectroscopic techniques over a frequency...
Photoconductive antennas (PCA) (one of the most commonly used terahertz emitters) have limited performance (e.g. low output power) and as such, do not fully meet the increasing needs of applications. This work attempts to find a route to further improve the performance of PCA by studying the dependence of emission properties on various parameters. Using substrates of LT-GaAs and SI-GaAs, the responses...
InAs/AlSb Heterostructure Backward Tunneling Diodes (HBTDs) were grown on semi-insulating GaAs (100) substrate using molecular beam epitaxy (MBE). The current-voltage characteristics of the InAs/AlSb HBTDs, both at room temperatures (RT) and cryogenic temperatures, have been studied as a function of the InAs buffer thickness. It has been found that a thicker InAs buffer doesn't improve the surface...
A monolithic tunable single mode terahertz quantum cascade laser source based on intra-cavity difference frequency generation with a tuning range of ∼580 GHz is demonstrated at room temperature.
Polystyrene composites with 0.25 wt. % loading of oriented multiwall carbon nanotubes (MWCNTs) have been produced by stretching method. The composites showed anisotropy of transmission of millimeter wave radiation depending on sample orientation relative to the polarization of electromagnetic wave.
We present room-temperature broadly tunable external cavity terahertz sources based on Cherenkov intra-cavity difference frequency generation in mid-infrared quantum cascade lasers bonded with Si substrate. Laser chips are integrated into a Littrow-type external cavity system. Devices demonstrate continuous THz emission tuning from 1.2 THz to 5.9 THz at room temperature with peak power output varying...
THz polarizing beamsplitters have been fabricated, and tested experimentally with high extinction ratios, and low insertion loss. These new beamsplitters are substrate based and manufactured from simple materials, and are consequently very affordable. The performance of these beamsplitters is enhanced using structured-surface-plasmons and bi-periodic, high “effective-fill-factor.”
Negative-type liquid crystal material, which has an inverse dielectric anisotropy for the low frequency, is introduced on a microstripline for modulating its dielectric constant with low driving voltage and low power consumption. Since the molecular orientation response for the driving voltage is inverted in comparison with positive-type LC materials, the transmission MMW phase magnitude decreases...
Terahertz photoconductive antenna arrays with interdigitated electrodes are laid down on GaAs substrates in which different geometries are assessed for their ability to enhance performance of a time-domain spectrometer (TDS) system.
The effects of bending a 2-dimensional planar array of rectangular split-ring resonators (SRRs) is observed by mounting the array to varying diameter HDPE cylinders. By studying the transmission of pulsed THz light through the SRR-cylinder system, it shown that the resonant frequency and response of the arrays are tunable as a function of the radius of curvature.
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