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0kunev, 0.; Dzardanov, A.; Ekstrom, H.; Jacobsson, S.; Kollberg, E.; Gol'tsman, G.; Gershenzon, E. |
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Title |
NbN hot electron waveguide mixer for 100 GHz operation |
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1994 |
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Proc. 5th Int. Symp. Space Terahertz Technol. |
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Proc. 5th Int. Symp. Space Terahertz Technol. |
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214-224 |
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waveguide NbN HEB mixers |
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NbN is a promising superconducting material used to develope hot- electron superconducting mixers with an IF bandwidth over 1 GHz. In the 100 GHz frequency range, the following parameters were obtained for NbN films 50 A thick: the noise temperature of the receiver (DSB) 1000 K; the conversion losses 10 d13, the IF bandwidth 1 GHz; the local oscillator power 1 /LW. An increase of NbN film thickness up to 80-100 A and increase of working temperature up to 7-8 K, and a better mixer matching may allow to broader the IF band up to 3 Gllz, to reduce the conversion losses down to 3-5 dB and the noise tempera- ture down to 200-300 K. |
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1644 |
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Author |
Elantev, Andrey I.; Karasik, Boris S. |
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Title |
Noise temperature of a superconducting hot-electron mixer |
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1994 |
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Proc. 5th Int. Symp. Space Terahertz Technol. |
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Proc. 5th Int. Symp. Space Terahertz Technol. |
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225 |
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HEB mixers |
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1645 |
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Gershenzon, E. M.; Gol'tsman, G. N. |
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Title |
Hot electron superconductive mixers |
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1993 |
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Proc. 4th Int. Symp. Space Terahertz Technol. |
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Proc. 4th Int. Symp. Space Terahertz Technol. |
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618-622 |
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HEB mixers |
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1656 |
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Gol'tsman, G. N.; Elant'iev, A. I.; Karasik, B. S.; Gershenzon, E. M. |
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Title |
Antenna – coupled superconducting electron-heating bolometer |
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Conference Article |
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1993 |
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Proc. 4th Int. Symp. Space Terahertz Technol. |
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Proc. 4th Int. Symp. Space Terahertz Technol. |
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623-628 |
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HEB |
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We propose a novel antenna-coupled superconducting bolometer based on electron-heating in the resistive state. A short narrow ultrathin super- conducting film strip (sized approximately 4x1x0.01 pm 3 ), which is in good thermal contact with the thermostat, serves as a resistive load for infrared or submillimeter current. In contrast to conventional isothermal super- conducting bolometers electron-heating ones can have a higher sensitivity which grows when filni. thickness is reduced. Response time of electron- heating bolometer does not depend on heat transfer from the film to the enviroment. To calculate the sensitivity (NEP), we have used experimental data on wideband Al, Nb and NbN bolometers which have the same un- derlying physical mechanism. The bolom.eters have been made in the form of a structure composed of a number of long narrow strips. The values of for Al, NEP have been found to be 1.5 . 113 -16 1 140 -15 ) and 2 . 10 – 14werT,-1/2 – Nb and NbN respectively. In the paper, the prospects are also discussed of improving the picosecond YBaCuO detector, developed recently. NEP value of the detector, if combined with a microantenna, can reach the order of 10- •ilz-v2. |
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1657 |
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Neroev, V. V.; Iomdina, E. N.; Khandzhyan, A. T.; Khodzhabekyan, N. V.; Sengaeva, M. D.; Ivanova, A. V.; Seliverstov, S. V.; Teplyakova, K. O.; Goltsman, G. N. |
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Experimental study of the effect of corneal hydration and its biomechanical properties on the results of photorefractive keratectomy |
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2021 |
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Vestn. Oftalmol. |
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Vestn. Oftalmol. |
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137 |
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3 |
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68-75 |
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THz scanning, cornea, photorefractive keratectomy, medicine |
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Abstract |
Water content in the cornea may affect the outcome of its excimer laser ablation, especially in presbyopic patients with myopic refraction. This hypothesis can be tested by scanning the cornea in the terahertz (THz) range to determine its hydration level.
Purpose: To study the effect of hydration of the cornea determined by non-contact THz scanning and its biomechanical parameters on the results of photorefractive keratectomy (PRK) in an experiment.
Material and methods: PRK was performed using the Nidek EC-5000 QUEST excimer laser on 8 rabbit eyes. Corneal hydration was evaluated by determining the reflection coefficient (RC) in the THz electromagnetic radiation range before PRK, after 3-5 days, and after 1, 2, 3, and 4 months. Clinical examination included autorefractometry, assessment of corneal thickness and other anatomical and optical parameters of the anterior eye segment (Galilei G6, Ziemer Ophthalmic Systems AG 6.0.2, Switzerland), measurement of corneal hysteresis (CH) and corneal resistance factor (CRF) using the Ocular Response Analyzer (ORA; Reichert, USA), as well as tear production (Schirmer test).
Results: The initial water content in the cornea has a significant effect on the thickness of the removed layer, i.e. on the PRK effect, with correlation coefficient of Rs= -0.976 (p<0.01). The correlation between CH and the ablation depth is less pronounced (Rs=0.643), and CRF had no correlation with it (Rs= -0.089). Biomechanical indicators of the cornea depend on its hydration: changes in CH and CRF after excimer laser ablation qualitatively coincide with changes in RC, the correlation coefficient between RC and the initial value of CH is R= -0.619 (moderate negative correlation).
Conclusion: THz scanning is an effective non-contact technology for monitoring corneal hydration level. The mismatch of the hypoeffect of keratorefractive excimer laser intervention planned for patients with presbyopia with the actual outcome can be caused by individual decrease in the initial water content in the cornea. |
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Russian |
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1794 |
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