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| Author |
Darula, Marian; Semenov, Alex D.; Hübers, Heinz-Wilhelm; Schubert, Josef |
| Title |
Quasioptical high-Tc superconductor Josephson mixer at terahertz frequencies |
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Abstract |
| Year |
2000 |
Publication |
Proc. 11th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 11th Int. Symp. Space Terahertz Technol. |
| Volume |
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Pages |
515 |
| Keywords |
HTS Josephson mixers |
| Abstract |
Mixers based on Josephson junctions from conventional superconductor materials have demonstrated excellent performance at subgap frequencies. The advantages of Josephson mixers are low optimal power of the local oscillator and large intermediate frequency bandwidth but their noise temperature increases dramatically at frequencies corresponding to the energy gap of the superconductor, which is typically below 1 THz for widely used materials. The large energy gap of oxide superconductors makes them promising candidates for development of terahertz Josephson mixers. Here we report on experimental study of the quasioptical mixer utilizing bicrystal Josephson junction from high-transition-temperature YBa 2 Cu 3 O 7-δ film. Junctions with a width of 2 µm were fabricated from 100 nm thick laser ablated films on bicrystal MgO substrates and had the and the J C R n product of about 2 mV at 4.2 K. The planar complementary logarithmic spiral antenna incorporated into co-planar waveguide was patterned from 200 nm thick gold film thermally evaporated in situ on top of the YBa 2 Cu 3 O 7-δ film. The mixer chip was clamped to the extended hemispherical silicon lens. Performance of the mixer was investigated at 4.5 K bath temperature. We used FIR laser as a local oscillator at frequencies 0.698 and 2.52 THz. System noise temperature (DSB) was determined from Y-factor measured with 300 K and 77 K loads. At 0.698 THz the lowest noise temperature 1750 K was observed when the mixer was biased with the fixed current to the region in the vicinity of either the first Shapiro step or the critical current. Between these two bias points the noise temperature increased to ≈ 20000 K. As function of the local oscillator power the noise temperature reached the minimum when the critical current was suppressed to the half of its equilibrium value. Power of the local oscillator absorbed by the mixer at optimal operation was of the order 100 nW. The present design of our antenna limits the upper operation frequency to the value of 1.8 THz. Nevertheless, we clearly observed Shapiro steps at the frequency 2.52 THz. Bearing in mind an improved design of the antenna, we estimate the 3000 K DSB noise temperature at this frequency. |
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1555 |
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Cherednichenko, S.; Rönnung, F.; Gol’tsman, G.; Kollberg, E.; Winkler, D. |
| Title |
YBa2Cu3O7-δ hot-electron bolometer mixer at 0.6 THz |
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Conference Article |
| Year |
2000 |
Publication |
Proc. 11th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 11th Int. Symp. Space Terahertz Technol. |
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517-522 |
| Keywords |
YBCO HTS HEB mixers |
| Abstract |
We present an investigation of hot-electron bolometric mixer based on a YBa 2 Cu 3 O 7-δ (YBCO) superconducting thin film. Mixer conversion loss of –46 dB, absorbed local oscillator power and intermediate frequency bandwidth were measured at the local oscillator frequency 0.6 THz. The fabrication technique for nanoscale YBCO hot-electron bolometer (HEB) mixer integrated with a planar antenna structure is described. |
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1556 |
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Cherednichenko, S.; Kroug, M.; Yagoubov, P.; Merkel, H.; Kollberg, E.; Yngvesson, K. S.; Voronov, B.; Gol’tsman, G. |
| Title |
IF bandwidth of phonon cooled HEB mixers made from NbN films on MgO substrates |
Type |
Conference Article |
| Year |
2000 |
Publication |
Proc. 11th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 11th Int. Symp. Space Terahertz Technol. |
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219-227 |
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NbN HEB mixers, cinversion gain bandwidth, IF bandwidth |
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An investigation of gain and noise bandwidth of phonon-cooled hot-electron bolometric (HEB) mixers is presented. The radiation coupling to the mixers is quasioptical through either a spiral or twin-slot antenna. A maximum gain bandwidth of 4.8 GHz is obtained for mixers based on a 3.5 nm thin NbN film with Tc= 10 K. The noise bandwidth is 5.6 GHz, at the moment limited by parasitic elements in the, device mount fixture. At 0.65 THz the DSB receiver noise temperature is 700-800 К in the IF band 1-2 GHz, and 1150-2700 К in the band 3.5-7 GHz. |
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1557 |
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Yngvesson, K. S.; Gerecht, E.; Musante, C. F.; Zhuang, Y.; Ji, M.; Goyette, T. M.; Dickinson, J. C.; Waldman, J.; Yagoubov, P. A.; Gol’tsman, G. N.; Voronov, B. M.; Gershenzon, E. M. |
| Title |
Low-noise HEB heterodyne receivers and focal plane arrays for the THz regime using NbN |
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Conference Article |
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1999 |
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Proc. SPIE |
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Proc. SPIE |
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3795 |
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357-368 |
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NbN HEB mixers |
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We have developed prototype HEB receivers using thin film superconducting NbN devices deposited on silicon substrates. The devices are quasi-optically coupled through a silicon lens and a self-complementary log-specific toothed antenna. We measured DSB receiver noise temperatures of 500 K (13 X hf/2k) at 1.56 THz and 1,100 K (20 X hf/2k) at 2.24 THz. Noise temperatures are expected to fall further as devices and quasi-optical coupling methods are being optimized. The measured 3 dB IF conversion gain bandwidth for one device was 3 GHz, and it is estimated that the bandwidth over which the receiver noise temperature is within 3 dB of its minimum value is 6.5 GHz which is sufficient for a number of practical applications. We will discuss our latest results and give a detailed description of our prototype setup and experiments. We will also discuss our plans for developing focal plane arrays with tens of Hot Electron Bolometric mixer elements on a single silicon substrate which will make real time imaging systems in the THz region feasible. |
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SPIE |
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Hwu, R.J.; Wu, K. |
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Terahertz and Gigahertz Photonics |
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1561 |
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Cherednichenko, S.; Ronnung, F.; Gol'tsman, G.; Gershenzon, E.; Winkler, D. |
| Title |
YBa2Cu3O7-δ hot-electron bolometer with submicron dimensions |
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Conference Article |
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1999 |
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Proc. 10th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 10th Int. Symp. Space Terahertz Technol. |
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181-189 |
| Keywords |
YBCO HTS HEB mixers |
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Photoresponse of YBa2Cu3O7-δ hot-electron bolometers to modulated near-infrared radiation was studied at a modulation .frequenc y var y ing from 0.2 MHz to 2 GHz. Bolometers were _fabricated from a 50 12 M thick film and had in-plane areas of 10x10 , um 2 . 2x0.2 s um', 1x0.2 p.m', and 0.5x0.2 jim. We found that nonequilibrium phonons cool down more effectively for the bolometers with smaller area. For the smallest bolometer the bolometric component in the response is 10 dB less than for the largest one. |
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1572 |
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