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We discuss measurement system and method for establishing traceability of terahertz (THz) power to NIST standards over a 0.3 to 7.5 THz range. In addition, we describe the performance of an electrically-calibrated thermopile detector, which is used as the NIST standard for THz power measurements. Specifically, we present measurements of the reflectance and spatial uniformity of the thermopile detector.
We have developed a calorimeter for a metrology standard for measuring the power of terahertz (THz) waves. Since the THz calorimeter is based on the thermal balance between heat produced by THz waves and direct current (DC), it requires an equivalent factor for converting from THz to DC power. The DC equivalent factor, which is defined as the ratio between the thermal efficiency of THz and DC powers,...
A calorimetric power meter has been developed for the highly accurate power measurement of terahertz spatial light. A solid-state terahertz absorber is used when constant terahertz wave absorption occurs due to the dielectric loss of the absorber and the sensor frequency sensitivity can be calibrated by measuring the reflectance characteristics of the absorber in the terahertz region. The stable absorption...
In this paper, we report the repeatability of calorimetric measurement of absolute terahertz (THz) power at room temperature. Highly sensitive measurement at a sub-microwatt level was performed by using a calorimeter based on an isothermal temperature-control technique. The experiment was demonstrated at 1 THz using a photomixer as a THz source. Type A uncertainty in repeatability was evaluated to...
The development of the modular short-pulse pre-prototype as base for the 2 MW, 170 GHz, CW coaxial-cavity gyrotron for ITER upgrade and beyond is in progress at Karlsruhe Institute of Technology (KIT). The current modular pre-prototype configuration allows the generation of >2 MW RF output power in short-pulses with a reasonable electronic efficiency of approximately 30 % without depressed collector...
Evanescent holes in a curved mirror will be used to provide an ultra-stable high-loss path to monitor the power in a 94 GHz transmitted beam for the Pulsed Cloud Radar on the EarthCARE satellite. Here we present details of the calculations to determine the hole size necessary and preliminary measurements on functional and proto-flight models.
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.”
The electron cyclotron heating and current drive (ECH/ECCD) gyrotron complex on the DIII-D tokamak is being upgraded with the addition of new gyrotrons. The transmitted power monitoring in the high power millimeter wave transmission system will be upgraded with new rf power monitors sensitive to the wave polarization and mode content. The speed of the real time steering antenna is being increased...
Reflection phase gratings offer great potential as local oscillator beam multiplexers in THz imaging heterodyne receivers. Using the Lagrange's multipliers method, we have optimized the phase profiles to achieve high diffraction efficiencies for three, four and five beam linear multiplexers. Experimental results at 2.5 THz are reported for a three-beam bulk aluminum multiplexing device.
A Comparison of THz power radiated from dc biased SWCNT, Graphene and Palladium thin films is performed. By controlling the bandwidth using an edge-fed or center-fed antenna, we aim to indirectly probe the radiation mechanism by measuring the total radiated power. The main goal is to compare the measured power with a standard Nyquist thermal noise model.
PTB, the National Metrology Institute of Germany, and Sensor- and Lasertechnik, a company based in Germany, developed together novel THz detectors. They are based on a coated thin film pyroelectric foil. Intensive care has been taken to their sensitivity and spectral response to make them suitable for absolute power measurement of time-domain spectroscopy systems (TDS). Their power responsivity is...
We have extended the discovery of ultrafast extrinsic photoconductivity in ErA:GaAs to the 1550 nm-driven continuous-wave (CW) photomixer. The photocurrent in the photomixer has been measured as a function of 1550 nm laser power and bias voltage. Then the first ever 1550 nm ErAs:GaAs photomixing transceiver was setup and THz power was successfully measured. The work done here represents the first...
Recent outstanding results achieved with the HIFI instrument on board the Herschel Space Telescope are driving a new generation of high-resolution coherent detectors in the terahertz range, not only for astrophysics but also for planetary science and Earth science missions. Schottky based receivers in the THz range and advanced receiver topologies such as compact arrays and side-band-separation require...
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