| Records |
| Author |
Semenov, A.; Richter, H.; Hübers, H.-W.; Petrenko, D.; Tretyakov, I.; Ryabchun, S.; Finkel, M.; Kaurova, N.; Gol’tsman, G.; Risacher, C.; Ricken, O.; Güsten, R. |
| Title |
Optimization of the intermediate frequency bandwidth in the THz HEB mixers |
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Abstract |
| Year |
2014 |
Publication |
Proc. 25th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 25th Int. Symp. Space Terahertz Technol. |
| Volume |
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Issue |
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Pages |
54 |
| Keywords |
NbN HEB mixer |
Abstract  |
We report on the studies of the intermediate frequency (IF) bandwidth of quasi-optically coupled NbN hot-electron bolometer (HEB) mixers which are aimed at the optimization of the mixer performance at terahertz frequencies. Extension of the IF bandwidth due to the contribution of electron diffusion to the heat removal from NbN microbolometers has been already demonstrated for NbN HEBs at subterahertz frequencies. However, reducing the size of the microbolometer causes degradation of the noise temperature. Using in-situ multilayer manufacturing process we succeeded to improve the transparency of the contacts for electrons which go away from microbolometer to the metallic antenna. The improved transparency and hence coupling efficiency counterbalances the noise temperature degradation. HEB mixers were tested in a laboratory heterodyne receiver with a narrow-band cold filter which allowed us to eliminate direct detection. We used a local oscillator with a quantum cascade laser (QCL) at a frequency of 4.745 THz [1] which was developed for the H-Channel of the German Receiver for Astronomy at Terahertz frequencies (GREAT). Both the noise and gain bandwidth were measured in the IF range from 0.5 to 8 GHz using the hot-cold technique and preliminary calibrated IF analyzer with a tunable microwave filter. For optimized HEB geometry we found the noise bandwidth as large as 7 GHz. We compare our results with the conventional and the hot-spot mixer models and show that further extension of the IF bandwidth should be possible via improving the sharpness of the superconducting transition. The cross characterization of the HEB mixer was performed in the test bed of GREAT at the Max-Planck-Institut für Radioastronomie with the same QCL LO and delivered results which were consistent with the laboratory studies. |
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1359 |
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Semenov, A. D.; Gousev, Y. P.; Nebosis, R. S.; Renk, K. F.; Yagoubov, P.; Voronov, B. M.; Gol’tsman, G. N.; Syomash, V. D.; Gershenzon, E. M. |
| Title |
Heterodyne detection of THz radiation with a superconducting hot‐electron bolometer mixer |
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Journal Article |
| Year |
1996 |
Publication |
Appl. Phys. Lett. |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
69 |
Issue |
2 |
Pages |
260-262 |
| Keywords |
NbN HEB mixers |
| Abstract |
We report on the use of a superconducting hot‐electron bolometer mixer for heterodyne detection of terahertz radiation. Radiation with a wavelength of 119 μm was coupled to the mixer, a NbN microbridge, by a hybrid quasioptical antenna consisting of an extended hyperhemispherical lens and a planar logarithmic spiral antenna. We found, at an intermediate frequency of 1.5 GHz, a system double side band noise temperature of ≊40 000 K and conversion losses of 25 dB. We also discuss the possibilities of further improvement of the mixer performance. |
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0003-6951 |
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1610 |
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Ryabchun, S.; Tong, C.-yu E.; Blundell, R.; Kimberk, R.; Gol’tsman, G. |
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Effect of microwave radiation on the stability of terahertz hot-electron bolometer mixers |
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Conference Article |
| Year |
2006 |
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Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
| Volume |
6373 |
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63730J (1 to 5) |
| Keywords |
NbN HEB mixers, hot-electron bolometer mixers, stability, Allan variance, LO power fluctuations |
| Abstract |
We report our studies of the effect of microwave radiation, with a frequency much lower than that corresponding to the energy gap of the superconductor, on the performance of the NbN hot-electron bolometer (HEB) mixer incorporated into a THz heterodyne receiver. It is shown that exposing the HEB mixer to microwave radiation does not result in a significant rise of the receiver noise temperature and degradation of the mixer conversion gain so long as the level of microwave power is small compared to the local oscillator drive. Hence the injection of a small, but controlled amount of microwave radiation enables active compensation of local oscillator power and coupling fluctuations which can significantly degrade the stability of HEB mixer receivers. |
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SPIE |
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Anwar, M.; DeMaria, A.J.; Shur, M.S. |
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Terahertz Physics, Devices, and Systems |
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1441 |
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Hajenius, M.; Yang, Z. Q.; Gao, J. R.; Baselmans, J. J. A.; Klapwijk, T. M.; Voronov, B.; Gol'tsman, G. |
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Optimized sensitivity of NbN hot electron bolometer mixers by annealing |
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Journal Article |
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2007 |
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IEEE Trans. Appl. Supercond. |
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IEEE Trans. Appl. Supercond. |
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17 |
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2 |
Pages |
399-402 |
| Keywords |
NbN HEB mixers |
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We report that the heterodyne sensitivity of superconducting hot-electron bolometers (HEBs) increases by 25-30% after annealing at 85degC in high vacuum. The devices studied are twin-slot antenna coupled mixers with a small area NbN bridge of 1 mum times 0.15 mum, above which there is a SiO 2 passivation layer. The mixer noise temperature, gain, and resistance versus temperature curve of a HEB before and after annealing are compared and analysed. We show that the annealing reduces the intrinsic noise of the mixer by 37% and makes the superconducting transition of the bridge and the contacts sharper. We argue that the reduction ofthe noise is mainly due to the improvement of the transparency of the contact/film interface. The lowest receiver noise temperature of 700 K is measured at a local oscillator frequency of 1.63 THz and at a bath temperature of 4.2 K. |
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1051-8223 |
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1426 |
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Shurakov, A.; Tong, C.-Y. E.; Blundell, R.; Kaurova, N.; Voronov, B.; Gol'tsman, G. |
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Microwave stabilization of a HEB mixer in a pulse-tube cryocooler |
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Journal Article |
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2013 |
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IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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23 |
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3 |
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1501504-1501504 |
| Keywords |
NbN HEB mixers |
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We report the results of our study of the stability of an 800 GHz hot electron bolometer (HEB) mixer cooled with a pulse-tube cryocooler. Pulse-tube cryocoolers introduce temperature fluctuations as well as mechanical vibrations at a frequency of ~1 Hz, both of which can cause receiver gain fluctuations at that frequency. In our system, the motor of the cryocooler was separated from the cryostat to minimize mechanical vibrations, leaving thermal effects as the dominant source of the receiver gain fluctuations. We measured root mean square temperature variations of the 4 K stage of ~7 mK. The HEB mixer was pumped by a solid state local oscillator at 810 GHz. The root mean square current fluctuations at the low noise operating point (1.50 mV, 56.5 μA) were ~0.12 μA, and were predominantly due to thermal fluctuations. To stabilize the bias current, microwave radiation was injected to the HEB mixer. The injected power level was set by a proportional-integral-derivative controller, which completely compensates for the bias current oscillations induced by the pulse-tube cryocooler. Significant improvement in the Allan variance of the receiver output power was obtained, and an Allan time of 5 s was measured. |
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1051-8223 |
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1372 |
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