| 1. |
- Barrientos, C. Z., et al.
(author)
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Vertically illuminated TW-UTC photodiodes for terahertz generation
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 405-408
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Conference paper (peer-reviewed)abstract
- More efficient continuous-wave photonic nearinfrared mixers as terahertz sources are investigated with the motivation to develop a universal photonic local oscillator for astronomical submillimeter/terahertz receiver systems. For this, our group has developed new concepts for vertically illuminated traveling-wave (TW) photomixers. The new device called TWUni- Travelling Carrier photodiodes (TW-UTC PD) was simulated, modeled and shall be optical/terahertz tested at the Electrical Engineering Department of the University of Chile, whereas device fabrication is performed at the MC2 cleanroom facility at Chalmers University of technology. We are reporting on first progresses in this direction.
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| 2. |
- Billade, Bhushan, 1982, et al.
(author)
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ALMA band 5 cartridge performance
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 112-
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Conference paper (peer-reviewed)abstract
- Work presented here concerns the design and performance of the ALMA Band 5 cold cartridge, one of the 10 frequency channels of ALMA project, a radio interferometer under construction at Atacama Desert in Chile. The Band 5 cartridge is a dual polarization receiver with the polarization separation performed by orthomode transducer (OMT) [1]. For each polarization, Band 5 receiver employs sideband rejection (2SB) scheme based on quadrature layout, with SIS mixers covering 163-211 GHz with 4-8 GHz IF. The LO injection circuitry is integrated with mixer chip and is implemented on the same substrate, resulting in a compact 2SB assembly. Amongst the other ALMA bands, the ALMA Band 5 being the lowest frequency band that uses all cold optics, has the largest mirror. Consequently, ALMA Band 5 mirror along with its support structure leaves very little room for placing OMT, mixers and IF subsystems. The constraints put by the size of cold optics and limited cartridge space, required of us to revise the original 2SB design and adopt a design where all the components like OMT, mixer, IF hybrid, isolators and IF amplifier are directly connected to each other without using any co-ax cables in-between. The IF subsystem uses the space between 4 K and 15 K stage of the cartridge and is thermally connected to 4 K stage. Avoiding co-ax cabling required use of custom designed IF hybrid, furthermore, due to limited cooling capacity at 4 K stage, resistive bias circuitry for the mixers is moved to 15 K stage and the IF hybrid along with an integrated bias-T is implemented using superconducting micro-strip lines. The E-probes for both LO and RF waveguide-to-microstrip transitions are placed perpendicular to the wave direction (back-piece configuration). The RF choke at the end of the probes provides a virtual ground for the RF/LO signal, and the choke is DC grounded to the chassis. The on-chip LO injection is done using a microstrip line directional coupler with slot-line branches in the ground plane. The isolated port of the LO coupler is terminated by floating wideband elliptical termination. The mixer employs two SIS junctions with junction area of 3 μm2 each, in twin junction configuration, followed by a quarter wave transformer to couple it to the signal probe. A quarter-wave high impedance line on an extra layer of SiO2 is used to extract the IF by separating from RF [2]. At the conference, we plan to present details of the cartridge design and results of the experimental characterization of the ALMA Band 5 cold cartridge.
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| 3. |
- Cherednichenko, Serguei, 1970, et al.
(author)
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Water vapor radiometer for ALMA: Optical design and verification
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 340-
-
Conference paper (peer-reviewed)abstract
- Atacama Large Millimeter wave Array (ALMA) is being built at a high altitude Atacama Desert in Chile. It will consist of 50 12m telescopes with heterodyne instruments to cover a large frequency range from about 30GHz to nearly 1THz. In order to facilitate the interferometer mode of operation all receivers have to be phase synchronized. It will be accomplished by phase locking of all local oscillators from a single reference source. However, a noticeable part of the phase error is caused as the signal propagates through the Earth atmosphere. Since this effect originates from the fluctuations of water vapors, it can be accounted for by carefully measuring the spectral width of one of water vapor resonance absorption lines. This will be done with a submillimeter heterodyne radiometer, Water Vapor Radiometer (WVR) [1]. WVR will measure the sky brightness temperature in the beam path of every telescope across the 183GHz water line with a spectral resolution of about 1GHz. Accuracy of the calculated optical delay is determined by the combination of the radiometric accuracy of the WVR and of the errors originated in the WVR illumination of the telescope. We will describe major challenges in the design of the WVR to comply with the stringent requirements set to the WVR. Several approaches to simulate the quasioptical waveguide which brings the signal from the telescope's subreflector to the mixer horn, were used: fundamental mode Gaussian beam propagation, combined ray tracing with diffraction effects (using package ZEMAX), and a full vector electromagnetic simulations (using GRASP). The computational time increases rapidly from the first method to the last one. We have found that ZEMAX results are quite close to the one from GRASP, however obtained with nearly instant computation, which allows multiple iterations during system optimization. The beam pattern of the WVR and of WVR with the optical Relay (used to bring the signal from the telescope's main axis to the WVR input window) was measured by a scalar beam scan at four planes in the far field. The experimental results correspond to the simulated ones with a high accuracy. The WVR illuminates the telescope subreflector with a spillover of less than 1.5% while maintaining high aperture efficiency. We developed an approach to calculate the beam center position at the subreflector (with is at 6m from the WVR) from our test data (at maximum 2m from the WVR) in order confirm the maximum beam deviation does not exceed 20mm, i.e. 1/15 of the beam width.
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| 4. |
- Henke, D., et al.
(author)
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Modeling SIS junction arrays for APEX band 3 (385-500 GHz)
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 381-388
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Conference paper (peer-reviewed)abstract
- Abstract- A methodology for the modeling of superconductinginsulator- superconducting (SIS) junction arrays will be presented and compared with measured results. In many cases, junction arrays (either in parallel or series) are treated as a single equivalent junction. The APEX Band 3 (385-500 GHz) receiver design has been implemented with two junctions connected in parallel via a section of inductive microstrip line. In this case, it is desirable to separately model each junction as the pumping between junctions is no longer symmetrical across the entire band. Since the performance of the SIS junction depends on its terminating network, a complicated interaction occurs when another junction is part of the embedding impedance and, therefore, there remain aspects of its performance that are difficult to analyse. A simplified model, demonstrated with MATLAB, will be given and compared with a more complete model implemented using a common circuit simulator, Agilent ADS. In both cases, each junction is represented by a quasi 5-port network determined using the quantum theory of mixing. The model is then used to predict the performance of the APEX Band 3 mixer and compared with measured results.
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| 5. |
- Kuzmin, Leonid, 1946
(author)
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Superconducting thermo-electric bolometer for cosmology instruments
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 47-50
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Conference paper (peer-reviewed)abstract
- A novel type of the zero-biased thermo-electric bolometer (TEB) is proposed. The bolometer is based on a Charge-to-Voltage Converter (CVC) with a Superconductor- Insulator-Normal (SIN) Tunnel Junction and a superconducting absorber. The absorption of photons in the absorber leads to excitation of quasiparticles with some fraction of charge imbalance, tunneling through the SIN junction and generation of voltage. The thermoelectric voltage is determined by accumulation of tunneling charge in an external capacitance. Conversion efficiency is very high and voltage values comparable with a superconducting gap are easily achieved. The zero-biased CVC-TEB can be effectively used for creation of an array of bolometers.
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| 6. |
- Liljedahl, Johanna, 1981, et al.
(author)
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Development of a HBV tripler for 0.6 THz
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 399-404
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Conference paper (peer-reviewed)abstract
- We report on the progress of the design of a HBV frequency tripler for 0.6 THz. The diode is based on the InGaAs/InAlAs/AlAs on InP material system, and the diode material and geometry has been optimised with regards to conversion efficiency. In designing the diode, it was found that self heating is the major limiting factor due to the poor thermal conductivity of InGaAs. The resulting HBV is a two-mesa diode from a three-barrier material, with a mesa area of 6×3 μm2, and is estimated to have a 6-7% conversion efficiency and 100 - 150 K self heating at an input power of 30 mW.
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| 7. |
- Mahashabde, Sumedh, 1985, et al.
(author)
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Focal plane array of thermo-electric bolometers
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 257-
-
Conference paper (peer-reviewed)abstract
- Novel concepts of the parallel and series array of Thermo-Electric Bolometers (TEB) with Superconductor-Insulator-Normal (SIN) Tunnel Junctions [1] have been proposed and realized for a distributed focal plane antenna. The arrays are developed for a pixel design based on arrays of TEBs coupled to a distributed slot antenna or dipole antenna [2] similar to array of Cold-Electron Bolometers (CEB) [3,4].
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| 8. |
- Nyström, Olle, 1979, et al.
(author)
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Integrated Setup for THz Receiver Characterization
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. P6-4
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Conference paper (peer-reviewed)abstract
- A highly versatile measurement setup has been built that allows complete characterization of the ALMA Band 5 cartridge. The measurement setup includes all necessary hardware and largely achieves automatic measurements for the system noise and sideband rejection with in-built optimization procedures. The measurement setup additionally comprises measurements of the receiver saturation, phase and amplitude stability, as well as optical beam characterization.
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| 9. |
- Otto, Ernst, 1971, et al.
(author)
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Cold-electron bolometer integrated with a unilateral finline
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 238-243
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Conference paper (peer-reviewed)abstract
- The Cold-Electron Bolometer (CEB) is a very sensitive millimetre-wave detector which is easy to integrate with planar circuits. CEB detectors have other important features such as high saturation power and very fast response. We have designed, fabricated and tested CEB detectors integrated across the slot of a unilateral finline on silicon substrate. Bolometers were fabricated using e-beam directwrite trilayer technology. The CEB performance was tested in a He3 sorption cryostat HELIOX-AC-V at a bath temperature of 280 mK. To reduce the background power radiation overheating the optical window in the cryostat was equipped with two low-pass filters with cut-off frequency 33 cm-1 and 100 cm-1 and 2 neutral density filters with 10 db attenuation each. DC IV curves were measured in a current bias mode, optical response was measured by irradiating samples with a microwave signal from IMPATT diode at 110 GHz modulated at 127 Hz. These tests were conducted by coupling power directly into the finline chip. The signal response was measured using a lock-in amplifier. The bolometer dark electrical noise equivalent power is estimated to be about NEP=5·10-16 W/Hz1/2.
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| 10. |
- Spasov, S., et al.
(author)
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Terahertz imaging with a highly-sensitive quantum dot detector
- 2010
-
In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 266-
-
Conference paper (peer-reviewed)abstract
- We report on an application of photon counting detector in the sub-terahertz range of electromagnetic waves for imaging of natural and stimulated radiation emitted by free standing objects. The detector is assembled from a GaAs/AlGaAs quantum dot, electron reservoir and quantum point contact (QPC). Its operation relies on photon-to-plasmon and plasmon-to-charge conversion, followed by charge measurement in a single-shot mode. Individual photons excite plasma waves in the quantum dot, with a resonance frequency determined by the shape of the QD confining potential. The plasma wave decays subsequently by single-particle electron-hole excitations, which change the electrostatic potential stepwise in the close proximity to the QD. The potential steps are probed with the QPC operating as a sensitive electrometer. A studied object is placed on a twodimensional translating stage. Its emission is projected through an optical window onto the detector attached to a 1K cold finger in a cryostat. Subsequently translating the stage in two space directions we are able to map the distribution of the emitted radiation. The presented technique has a potential for imaging of objects passively radiated in the sub-terahertz range.
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| 11. |
- Tang, Aik-Yean, 1980, et al.
(author)
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Parameter Extraction and Geometry Optimisation of Planar Schottky Diodes
- 2010
-
In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 361-
-
Conference paper (peer-reviewed)abstract
- The continuous interests in terahertz (300 GHz to 10 THz) applications have generated technology pressure in the search of reliable, room temperature operational and compact sources and detectors. Various terahertz sources such as optically pumped lasers, backward wave oscillators, and direct multiplied sources have been explored [1]. For direct multiplied sources, the GaAs-based Schottky diode is one of the most critical devices in heterodyne receivers operating at millimetre and sub-millimetre wavelengths. The importance of Schottky diode could be seen from the meticulous efforts in the diode technology advancement. This includes the evolvement of the whisker contact to the surface channel planar diode technology [2] as well as the circuit integration of the discrete Schottky diodes. For high frequency applications, the performance of a GaAs Schottky diode is limited by the parasitic elements [3] and the losses due to skin effects [4]. Thus, systematic studies of the Schottky diode parasitic elements and high frequency losses are very crucial in meeting the design goals. In the search of optimised diode performance, several studies on diode modelling have been performed [5], [6]. In this paper, we present a systematic method to estimate the diode geometry dependent parasitic elements and skin effect losses for diodes operating up to 400 GHz. Different diode geometries, such as padto- pad distance, buffer layer thickness and semi-insulating etch depth have been investigated. The equivalent circuit based method as in [7] has been used, where the parasitic elements are extracted through the least square error fitting of the S-parameters simulated in Ansoft HFSS simulator to the lumped equivalent circuit. Simulations are performed with the semi-insulating substrate of 3 μm (for the case of integrated diode on the membrane) and 10 μm (for the case of discrete diode). In addition, high frequency losses are investigated with the similar method, by using lossy conductors and adding a frequency dependent resistor in the lumped equivalent circuit. Analysis of the simulation and measurement results will be presented.
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| 12. |
- Tarasov, Mikhail, 1954, et al.
(author)
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Cold-electron bolometer array integrated with a 350 GHz cross-slot antenna
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 219-224
-
Conference paper (peer-reviewed)abstract
- Two series/parallel arrays of Cold-Electron Bolometers (CEB) with Superconductor-Insulator-Normal (SIN) tunnel junctions were integrated in orthogonal ports of a cross-slot antenna. The receiving system was designed for polarisation measurements in a 350 GHz frequency band with JFET readout at the BOOMERanG-FG balloon telescope. Each orthogonal array consists of 10 cold-electron bolometers connected in parallel for RF signal and in series for DC signal. The array was designed to increase the output resistance by a factor of 102 in comparison to a single CEB, for matching with JFET readout while maintaining the same conditions for RF coupling. The dynamic resistance of such array is 1 M5 at the bias point of maximal response. For the input microwave signal bolometers are connected in parallel. This provides matching to the 30 input impedance of a cross-slot antenna on Si substrate. The array of bolometers has a saturation power 10 times higher than a single bolometer. This significantly increases the dynamic range. With a measured temperature response of 8.8 μV/mK, a total absorber volume of 0.08 μm3, and an output noise of about 11 nV/Hz1/2, we estimated the dark electrical noise equivalent power as NEP=6*10-18 W/Hz1/2 at 280 mK. The optical response was measured using both hot/cold loads and a backward wave oscillator as sources of radiation.
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| 13. |
- Teyssier, D., et al.
(author)
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Herschel/HIFI In-flight commissioning and performance
- 2010
-
In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 23-28
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Conference paper (peer-reviewed)abstract
- The Herschel Space Observatory was successfully launched on the 14th of May, 2009, lifting into space the Heterodyne Instrument for the Far-Infrared (HIFI). After the standard early orbit operations on the Space-craft, the instrument was switched on for the first time on the 24th of May, kicking off an instrument Commissioning period of more than a month and a half. We present here the outcome of this Commissioning campaign, including the measured in-flight performance of the instrument. Among the challenges encountered during this period was the need to optimize the stability of the signal provided by the Local Oscillator (LO) chains in some of the frequency bands, in particular that covering the singly Ionized Carbon (C+) line at the upper edge of the HIFI range, and one of the backbones of the science program of the instrument. The same concept also allowed significant improvements in the upper end of the 3b LO chain. Another noticeable achievement was the very good co-alignment measured between the mixer beams in the respective H and V polarizations offered by HIFI, allowing for more than a simple build-in redundancy, as the observing efficiency will really benefits from the combination of the two mixers.
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| 14. |
- Zhao Ternehäll, Huan, 1982, et al.
(author)
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VNA-calibration and S-parameter characterization of submillimeter wave integrated membrane circuits
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 299-300
-
Conference paper (peer-reviewed)abstract
- A TRL-calibration kit enabling S-parameter characterization of membrane circuits has been developed for the WR-03 band. The TRL-design features 3 μm thick GaAs membrane circuits packaged in E-plane split waveguide blocks. Membrane filters have been characterized after the calibration.
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