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A new type of continuous-wave (CW) terahertz (THz) photomixer was fabricated using a single nanowire (Ø 120 nm) on low-temperature-grown (LTG) GaAs. The small diameter of the nanowire reduces the device capacitance by a factor of more than 10 compared to photomixers with conventional interdigital fingers. Furthermore, the single nanowire can handle currents > 20 mA without electromigration enabling...
A terahertz detector using an InAlAs/InGaAs high-electron-mobility-transistor (HEMT) integrated with a bow-tie antenna was proposed and fabricated. By utilizing ballistic transport in the short-channel, a current sensitivity of 1.5 A/W at 280 GHz was achieved by the detector having 70-nm T-gate HEMT without applying drain bias. We also measured the drain bias dependence of current sensitivity on the...
A novel beam scanning antenna in 0.2 Terahertz band based on frequency-scanning grating-reflector was studied in this paper. A bilayer structure is introduced and optimized to improve the diffraction efficiency and to suppress the specular beam. The frequency-controlled beam steering concept was verified by the quasi-optical measurements in 0.2THz band. The measured scanning range is 13.55° over the...
The design of dielectric wedge-scanned millimeter wave lens antennas with measured results is presented. The diffractive lens antenna (DLA) is treated; it incorporates a lens that transforms the radiation pattern of a scalar feedhorn. A schematic diagram of a zoned dielectric wedge-scanned DLA with Fresnel spherical surface is presented. An efficient device for scanning the beam produced by a DLA...
We report on the development of a tunable antenna coupled intersubband terahertz (TACIT) detector based on GaAs/AlGaAs two dimensional electron gas. A successful device design and micro-fabrication process have been developed which maintain the high mobility (1.1×106 cm2/V-s at 10K) of a 2DEG channel in the presence of a highly conducting backgate. Gate voltage-controlled device resistance and direct...
We are studying resonant-tunneling diodes (RTDs) with strong back injection of electrons from collector into quantum well. Such RTDs exhibit large negative differential conductance and they operate up to 1.46 THz in oscillators.
A FET detector, fabricated in a standard CMOS technology and coupled to a bow-tie antenna is characterized in terms of spatial response by using a deconvolution method. An optical setup is used to produce a predictable impulse response. The resulting spatial response shows interaction with other structures present on the chip, while the measured shape is in agreement with the antenna effective area...
Bow-tie antenna coupled field-effect transistors have been implemented in 0.25 μm AlGaN/GaN process technology and have been mounted on an aplanatic hemispherical silicon substrate lens. By asymmetric coupling of 590-GHz radiation to the channel, the transistors are used as direct power detectors, achieving system noise-equivalent power values of 166 pW/√Hz at 590 GHz (referred to the total beam power)...
This paper presents a 153–162 GHz pre-amplified power detector receiver based on a 250 nm InP/InGaAs/InP double heterojunction bipolar transistor (DHBT) process. The front end consists of a double slot antenna followed by a five stage low noise amplifier and a detector. The receiver is characterized through measurements of its response to broadband hot and cold terminations. A simplified method is...
Layered metasurfaces made of gold loop antennas are proposed for beam engineering at telecom band. Any transmitted amplitude or phase profile is designable by modifying the loop configuration cell by cell and layer by layer. Applications of 3D beam scanning and focusing are studied numerically and high efficiency of > 80% is achieved thanks to the low ohmic loss and the perfect impedance match...
We have proposed and fabricated an antenna-coupled microbolometer with a Joule-heating resistor at the center of a half-wave antenna on a Si substrate to achieve a high-performance sensing in 1 THz frequency region at a room-temperature. The heater is directly connected to a half-wave antenna at its center and the thermistor is thermally contacted to but electrically isolated from the heater by a...
We perform THz near-field measurements on bowtie antennas made of doped Si and gold. The measurements show a similar local field enhancement for the different materials. These measurements constitute the first demonstration of plasmonic near-field enhancement using semiconductors at THz frequencies. Semiconductors offer the possibility of ultrafast optical switching of plasmonic resonances (on a ps...
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...
The main objective of this paper is to present full-wave computational procedures and explicit equations leading to reproduce the experimental behavior of photoconductive antennas (PCAs) in the frame of time-domain spectroscopy systems. Additionally, the computational tools developed are aimed to analyze the efficiency of such antennas.
We present the performance of ErAs:GaAs photoconductive antennas measured with a 1550-nm time-domain spectrometer. The effect of the erbium concentration is studied in terms of spectrum and dynamic range. A 1%- and 2%-Er ErAs:GaAs PC switch were tested and showed detected frequencies up to at least 2.5 and 4 THz, respectively, with a low-frequency dynamic range of ∼50 and ∼55 dB.
A new method for modeling terahertz photoconductive antennas (THz-PCAs) is presented. The finite element method solver COMSOL® is utilized to combine Maxwell's, Poisson's and the Drift-Diffusion equations into a single 2D/3D multiphysics model. This model can then be used to computationally investigate and design THz-PCAs with more complex geometries compared with current numerical methods. Preliminary...
Dust emission is used in space applications for star-formation characterization normally acquired by different detectors operating at Infrared (IR) and sub-millimeter wave (sub-mm wave) frequencies. An integrated dual band detector working at both frequency ranges will be described in this paper. The proposed configuration implements a spiral antenna working at sub-millimeter wave frequencies whose...
In the pursuit of an uncooled THz sensor, we address the specific modeling and optimization method for micro-machined transistors for the implementation of antenna-coupled MOSFET bolometers. We discuss the degrees of freedom for maximizing the device's SNR, outlining also the trade-offs in relation to the requirements of an integrated read-out circuit. The methodology was applied to novel antenna-coupled...
The mechanism of the halfway power dependence Pn with 1<n<2 in the 1.5 μm excitation of low-temperature-grown GaAs was investigated and found to be well accounted for by a transition from linear to quadratic response.
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