| Records |
| Author |
Huebers, Heinz-Wilhelm; Pavlov, S.; Semenov, A.; Köhler, R.; Mahler, L.; Tredicucci, A.; Beere, H.; Ritchie, D.; Linfield, E. |
| Title |
Terahertz quantum cascade laser as local oscillator in a heterodyne receiver |
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Journal Article |
| Year |
2005 |
Publication |
Optics Express |
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Volume  |
13 |
Issue |
15 |
Pages |
5890-5896 |
| Keywords |
QCL heterodyne, 6 mW at 2.5 THz, HEB mixer, terahertz |
| Abstract |
Terahertz quantum cascade lasers have been investigated with respect to their performance as a local oscillator in a heterodyne receiver. The beam profile has been measured and transformed in to a close to Gaussian profile resulting in a good matching between the field patterns of the quantum cascade laser and the antenna of a superconducting hot electron bolometric mixer. Noise temperature measurements with the hot electron bolometer and a 2.5 THz quantum cascade laser yielded the same result as with a gas laser as local oscillator. |
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627 |
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Meledin, D.; Tong, C.-Y. E.; Blundell, R.; Goltsman, G. |
| Title |
Measurement of intermediate frequency bandwidth of hot electron bolometer mixers at terahertz frequency range |
Type |
Journal Article |
| Year |
2003 |
Publication |
IEEE Microw. Wireless Compon. Lett. |
Abbreviated Journal |
IEEE Microw. Wireless Compon. Lett. |
| Volume |
13 |
Issue |
11 |
Pages |
493-495 |
| Keywords |
waveguide NbN HEB mixers |
| Abstract |
We have developed a new experimental setup for measuring the IF bandwidth of superconducting hot electron bolometer mixers. In our measurement system we use a chopped hot filament as a broadband signal source, and can perform a high-speed IF scan with no loss of accuracy when compared to coherent methods. Using this technique we have measured the 3 dB IF bandwidth of hot electron bolometer mixers, designed for THz frequency operation, and made from 3-4 nm thick NbN film deposited on an MgO buffer layer over crystalline quartz. |
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1531-1309 |
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1509 |
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Loudkov, D.; Tong, C.-Y. E.; Blundell, R.; Kaurova, N.; Grishina, E.; Voronov, B.; Gol’tsman, G. |
| Title |
An investigation of the performance of the superconducting HEB mixer as a function of its RF embedding impedance |
Type |
Journal Article |
| Year |
2005 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
15 |
Issue |
2 |
Pages |
472-475 |
| Keywords |
waveguide NbN HEB mixers |
| Abstract |
We have conducted an investigation of the optimal embedding impedance for a waveguide superconducting hot-electron bolometric (HEB) mixer. Three mixer chip designs for 800 GHz, offering nominal embedding resistances of 70 /spl Omega/, 35 /spl Omega/, and 15 /spl Omega/, have been developed. We used both High Frequency Structure Simulator (HFSS) software and scale model impedance measurements in the design process. We subsequently fabricated HEB mixers to these designs using 3-4 nm thick NbN thin film. Receiver noise temperature measurements and Fourier Transform Spectrometer (FTS) scans were performed to determine the optimal combination of embedding impedance and normal-state resistance for a 50 Ohm IF load impedance. A receiver noise temperature of 440 K was measured at a local oscillator frequency 850 GHz for a mixer with normal state resistance of 62 /spl Omega/ incorporated into a circuit offering a nominal embedding impedance of 70 /spl Omega/. We conclude from our data that, for low noise operation, the normal state resistance of the HEB mixer element should be close to the embedding impedance of the mixer mount. |
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1439677 |
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1464 |
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Alda, Javier; Rico-García, José M.; López-Alonso, José M.; Boreman, G. |
| Title |
Optical antennas for nano-photonic applications |
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Journal Article |
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2005 |
Publication |
Nanotechnology |
Abbreviated Journal |
Nanotech. |
| Volume |
16 |
Issue |
5 |
Pages |
S230-S234 |
| Keywords |
optical antennas |
| Abstract |
Antenna-coupled optical detectors, also named optical antennas, are being developed and proposed as alternative detection devices for the millimetre, infrared, and visible spectra. Optical and infrared antennas represent a class of optical components that couple electromagnetic radiation in the visible and infrared wavelengths in the same way as radioelectric antennas do at the corresponding wavelengths. The size of optical antennas is in the range of the detected wavelength and they involve fabrication techniques with nanoscale spatial resolution. Optical antennas have already proved and potential advantages in the detection of light showing polarization dependence, tuneability, and rapid time response. They also can be considered as point detectors and directionally sensitive elements. So far, these detectors have been thoroughly tested in the mid-infrared with some positive results in the visible. The measurement and characterization of optical antennas requires the use of an experimental set-up with nanometric resolution. On the other hand, a computation simulation of the interaction between the material structures and the incoming electromagnetic radiation is needed to explore alternative designs of practical devices. |
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RPLAB @ gujma @ |
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734 |
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| Author |
Semenov, Alexei; Richter, Heiko; Smirnov, Konstantin; Voronov, Boris; Gol'tsman, Gregory; Hübers, Heinz-Wilhelm |
| Title |
The development of terahertz superconducting hot-electron bolometric mixers |
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Journal Article |
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2004 |
Publication |
Supercond. Sci. Technol. |
Abbreviated Journal |
Supercond. Sci. Technol. |
| Volume |
17 |
Issue |
5 |
Pages |
436-439 |
| Keywords |
NbN HEB mixers |
| Abstract |
We present recent advances in the development of NbN hot-electron bolometric (HEB) mixers for flying terahertz heterodyne receivers. Three important issues have been addressed: the quality of the source NbN films, the effect of the bolometer size on the spectral properties of different planar feed antennas, and the local oscillator (LO) power required for optimal operation of the mixer. Studies of the NbN films with an atomic force microscope indicated a surface structure that may affect the performance of the smallest mixers. Measured spectral gain and noise temperature suggest that at frequencies above 2.5 THz the spiral feed provides better overall performance than the double-slot feed. Direct measurements of the optimal LO power support earlier estimates made in the framework of the uniform mixer model. |
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357 |
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