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Dive into the research topics where Alexey A. Karpov is active.

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Featured researches published by Alexey A. Karpov.


IEEE Transactions on Applied Superconductivity | 2007

Low Noise 1 THz–1.4 THz Mixers Using Nb/Al-AlN/NbTiN SIS Junctions

Alexey A. Karpov; David W. Miller; Frank Rice; J. A. Stern; Bruce Bumble; H. G. LeDuc; Jonas Zmuidzinas

We present the development of a low noise 1.2 THz and 1.4 THz SIS mixers for heterodyne spectrometry on the Stratospheric Observatory For Infrared Astronomy (SOFIA) and Herschel Space Observatory. This frequency range is above the limit for the commonly used Nb quasi particle SIS junctions, and a special type of hybrid Nb/AlN/NbTiN junctions has been developed for this project. We are using a quasi-optical mixer design with two Nb/AlN/NbTiN junctions with an area of 0.25. The SIS junction tuning circuit is made of Nb and gold wire layers. At 1.13 THz the minimum SIS receiver uncorrected noise temperature is 450 K. The SIS receiver noise corrected for the loss in the LO coupler and in the cryostat optics is 350-450 K across 1.1-1.25 THz band. The receiver has a uniform sensitivity in a full 4-8 GHz IF band. The 1.4 THz SIS receiver test at 1.33-1.35 THz gives promising results, although limited by the level of available LO power. Extrapolation of the data obtained with low LO power level shows a possibility to reach 500 K DSB receiver noise using already existing SIS mixer.


Proceedings of SPIE | 2006

Development of 1.25 THz SIS mixer for Herschel Space Observatory

Alexey A. Karpov; David P. Miller; Frank Rice; J. A. Stern; Bruce Bumble; H. G. LeDuc; Jonas Zmuidzinas

We summarize the development and the delivery of two SIS mixers for the 1.1-1.25 THz band of the heterodyne spectrometer of Herschel Observatory (HSO). The quasi-optical SIS mixer has two Nb/AlN/NbTiN junctions with the area of 0.25 um2. The Josephson critical current density in the junction is 30-50 kA/cm2. The tuning circuit integrated with SIS junction has the base electrode of Nb and a gold wire layer. With the new SIS mixers the test receiver maximum Y factor is 1.41. The minimum receiver uncorrected DSB noise temperature is 450 K. The SIS receiver noise corrected for the loss in the optics is 350-450 K across the 1100-1250 GHz band. The receiver has a uniform sensitivity in the full IF range of 4-8 GHz. The sub-micron sized SIS junction shape is optimized to ease the suppression of the Josephson current, and the receiver operation is stable. The measured mixer beam pattern is symmetrical and, in a good agreement with the requirements, has the f/d =4.25 at the central frequency of the operation band. The minimum DSB SIS receiver noise is close to 6 hv/k, the lowest value achieved thus far in the THz frequencies range.


IEEE Transactions on Applied Superconductivity | 2009

Development of Low Noise THz SIS Mixer Using an Array of Nb/Al-AlN/NbTiN Junctions

Alexey A. Karpov; David P. Miller; J. A. Stern; Bruce Bumble; H. G. LeDuc; Jonas Zmuidzinas

We report the development of a low noise and broadband SIS mixer aimed for 1 THz channel of the Caltech Airborne Submillimeter Interstellar Medium Investigations Receiver (CASIMIR), designed for the Stratospheric Observatory for Infrared Astronomy, (SOFIA). The mixer uses an array of two 0.24 mum2 Nb/Al-AlN/NbTiN SIS junctions with the critical current density of 30-50 kA/cm2 . An on-chip double slot planar antenna couples the mixer circuit with the telescope beam. The mixer matching circuit is made with Nb and gold films. The mixer IF circuit is designed to cover 4-8 GHz band. A test receiver with the new mixer has a low noise operation in 0.87-1.12 THz band. The minimum receiver noise measured in our experiment is 353 K (Y = 1.50). The receiver noise corrected for the loss in the LO injection beam splitter is 250 K. The combination of a broad operation band of about 250 GHz with a low receiver noise makes the new mixer a useful element for application at SOFIA.


Archive | 2005

Low noise NbTiN 1.25 THz SIS mixer for Herschel Space Observatory

Alexey A. Karpov; David Harry Miller; Frank Rice; Jeffrey A. Stern; Bruce Bumble; Henry G. Leduc; Jonas Zmuidzinas


Archive | 2009

Broadband SIS mixer for 1 THz Band

Alexey A. Karpov; David Harry Miller; Jeffrey A. Stern; Bruce Bumble; H. G. LeDuc; Jonas Zmuidzinas


Archive | 2008

Low noise 1.4 THz SIS mixer for SOFIA

Alexey A. Karpov; David Harry Miller; Jeffrey A. Stern; Bruce Bumble; H. G. LeDuc; Jonas Zmuidzinas


Archive | 2008

Development of 1 THz SIS mixer for SOFIA

Alexey A. Karpov; David P. Miller; Jeffrey A. Stern; Bruce Bumble; H. G. LeDuc; Jonas Zmuidzinas


Archive | 2009

Low noise 1.2 THz SIS mixer for Herschel radio observatory

Alexey A. Karpov; David P. Miller; Frank Rice; J. A. Stern; Bruce Bumble; H. G. LeDuc; J. Zmuidzinasa


Archive | 2002

Low noise SIS mixer with Nb tuning circuit for the frequency above 1 THz

Alexey A. Karpov; Jonas Zmuidzinas; Frank Rice; David Harry Miller; Jeffrey A. Stern; Bruce Bumble; H. G. LeDuc


Archive | 2010

1.4 THz SIS Mixer Using Nb and Al Tuning Circuit

Alexey A. Karpov; D. Miller; J. A. Stern; F. Rice; H. G. LeDuc; J. Zmuidzinas

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Bruce Bumble

Jet Propulsion Laboratory

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H. G. LeDuc

Jet Propulsion Laboratory

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Jonas Zmuidzinas

California Polytechnic State University

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Frank Rice

California Institute of Technology

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Jeffrey A. Stern

California Institute of Technology

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J. A. Stern

Jet Propulsion Laboratory

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Henry G. Leduc

University of Southern California

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David W. Miller

Massachusetts Institute of Technology

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