Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Superconductor Science and Technology

Pushing the operating range of SIS mixers into the THz regime

T. M. Klapwijk, Pieter Dieleman, M. W. M. de Graauw

Published Dec 1, 1997• 5 citations
Publisher

Abstract

In recent years, responding to the need of the astronomical community, superconductor - insulator - superconductor (SIS) mixers have been developed to operate at THz frequencies. Best results are obtained by using niobium-based tunnel junctions with well-matched low-loss normal metal striplines, which are found to be less lossy than niobium striplines operated above the gap frequency of niobium (700 GHz). Niobium nitride tunnel junctions with a magnesium oxide tunnel barrier, although having reasonable-quality current - voltage characteristics, have been found to be unsuitable owing to excess shot noise resulting from pinholes in the barrier.

DOI
10.1088/0953-2048/10/12/003

Related papers

SIS and bolometer mixers for terahertz frequencies

K. H. Gundlach, Matthias Schicke

The need for extremely sensitive heterodyne receivers in the astronomical community has created strong efforts to develop appropriate frequency mixers. Nb/Al-Al x O y -Nb tunnel junctions with Nb matching circuits lead to best results up to approximately 700 GHz, the energy-gap frequency of Nb. For higher frequencies the Nb in the matching circuit becomes lossy and is replaced beyond 800 GHz by Al (which operates in the normal conducting state). The gap frequency of NbN is as high as 1.2 THz, but NbN technology is not yet mature. Practical films still have substantial radio frequency losses and the barrier of NbN tunnel junctions is too leaky. More recently, NbTiN, for which the gap frequency is also about 1.2 THz, was found to have very low losses, and is therefore a good choice for tuning circuits. New interesting tunnel junctions for mixers around 1 THz are NbTiN-MgO-NbTiN and Nb/Al-AlN x -NbTiN. Excellent performance from about 1 THz up to several terahertz can be expected from hot-electron transition-edge bolometer mixers. They consist of NbN or Nb microbridges, they do not need matching circuits and their frequency limit is not determined by the gap frequency.

Superconductor Science and Technology•Nov 23, 2000•20 citations

Development of SIS mixers for 1 THz

Jonas Stasys Zmuidzinas, J. Kooi, Jonathan H. Kawamura +4 more

SIS heterodyne mixer technology based on niobium tunnel junctions has now been pushed to frequencies over 1 THz, clearly demonstrating that the SIS junctions are capable of mixing at frequencies up to twice the energy gap frequency (4(Delta) /h). However, the performance degrades rapidly above the gap frequency of niobium (2(Delta) /h approximately equals 700 GHz) due to substantial ohmic losses in the on-chip tuning circuit. To solve this problem, the tuning circuit should be fabricated using a superconducting film with a larger energy gap, such as NbN; unfortunately, NbN films often have a substantial excess surface resistance in the submillimeter band. In contrast, the SIS mixer measurements we present in this paper indicate that the losses for NbTiN thin films can be quite low.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Jul 31, 1998•27 citations

THz SIS mixers with normal-metal Al tuning circuits

M. Bin, Michael C. Gaidis, Jonas Stasys Zmuidzinas +2 more

Nb-based superconductor - insulator - superconductor (SIS) mixers with Nb tuning circuits have demonstrated good results up to the Nb gap frequency. Above the gap frequency the performance is expected to degrade quickly because RF loss in Nb becomes significant. In this paper we present the results of an effort to extend Nb-based SIS mixers to THz frequencies by employing lower-loss normal-metal Al wiring and tuning structures. The SIS mixer has two Nb/Al-oxide/Nb junctions connected by an Al microstrip inductor. The direct detection response of the device was measured by a Fourier transform spectrometer. A double-side-band receiver noise temperature of 840 K was obtained at 1042 GHz when the device was operated at 2.5 K.

Superconductor Science and Technology•Apr 1, 1996•5 citations

Low-noise THz Niobium SIS Mixers

Mei Bin

This thesis describes the development of low-noise heterodyne receivers at THz frequencies for submillimeter astronomy using Nb-based superconductor-insulator-superconductor (SIS) tunneling junctions. The mixers utilize a quasi-optical configuration which consists of a planar twin-slot antenna and antisymmetrically-fed two-junctions on an antireflection-coated silicon hyperhemispherical lens. On-chip integrated tuning circuits, in the form of microstrip lines, are used to obtain maximum coupling efficiency in the designed frequency band. To reduce the rf losses in the integrated tuning circuits above the superconducting Nb gap frequency (~ 700 GHz), normal-metal Al is used to replace Nb as the tuning circuits. To account the rf losses in the micros trip lines, we calculated the surface impedance of the AI films using the nonlocal anomalous skin effect for finite thickness films. Nb films were calculated using the Mattis-Bardeen theory in the extreme anomalous limit. Our calculations show that the losses of the Al and Nb microstrip lines are about equal at 830 GHz. For Al-wiring and Nb-wiring mixers both optimized at 1050 GHz, the RF coupling efficiency of Al-wiring mixer is higher than that of Nb-wiring one by almost 50%. We have designed both Nb-wiring and Al-wiring mixers below and above the gap frequency. A Fourier transform spectrometer (FTS) has been constructed especially for the study of the frequency response of SIS receivers. This FTS features large aperture size (10 inch) and high frequency resolution (114 MHz). The FTS spectra, obtained using the SIS receivers as direct detectors on the FTS, agree quite well with our theoretical simulations. We have also, for the first time, measured the FTS heterodyne response of an SIS mixer at sufficiently high resolution to resolve the LO and the sidebands. Heterodyne measurements of our SIS receivers with Nb-wiring or Al-wiring have yielded results which arc among the best reported to date for broadband heterodyne receivers. The Nb-wiring mixers, covering 400 - 850 GHz band with four separate fixed-tuned mixers, have uncorrected DSB receiver noise temperature around 5hv/kb to 700 GHz, and better than 540 K at 808 GHz. An Al-wiring mixer designed for 1050 GHz band has an uncorrected DSB receiver noise temperature 840 K at 1042 GHz and 2.5 K bath temperature. Mixer performance analysis shows that Nb junctions can work well up to twice the gap frequency and the major cause of loss above the gap frequency is the rf losses in the microstrip tuning structures. Further advances in THz SIS mixers may be possible using circuits fabricated with higher-gap superconductors such as NbN. However, this will require high-quality films with low RF surface resistance at THz frequencies.

•Sep 1, 1997•8 citations

Low-noise 1 THz niobium superconducting tunnel junction mixer with a normal metal tuning circuit

M. Bin, Michael C. Gaidis, Jonas Stasys Zmuidzinas +2 more

We describe a 1 THz quasioptical SIS mixer which uses a twin-slot antenna, an antireflection-coated silicon hyperhemispherical lens, Nb/Al-oxide/Nb tunnel junctions, and an aluminum normal-metal tuning circuit in a two-junction configuration. Since the mixer operates substantially above the gap frequency of niobium (ν≳2Δ/h∼700 GHz), a normal metal is used in the tuning circuit in place of niobium to reduce the Ohmic loss. The frequency response of the device was measured using a Fourier transform spectrometer and agrees reasonably well with the theoretical prediction. At 1042 GHz, the uncorrected double-sideband receiver noise temperature is 840 K when the physical temperature of the mixer is 2.5 K. This is the first SIS mixer which outperforms GaAs Schottky diode mixers by a large margin at 1 THz.

Applied Physics Letters•Mar 18, 1996•97 citations

Low-noise THz-range Nb based SIS Receivers for Radio Astronomy

Kirill I. Rudakov, Andrey V. Khudchenko, Lyudmila V. Filippenko +4 more

This repost describes our results on development of low-noise heterodyne THz receivers for ground based and space radio astronomy. Superconductor-insulator-superconductor (SIS) mixers that employ high quality Nb-based tunnel junctions are the key element of the most sensitive heterodyne THz receivers. In particular we present here the SIS receivers for frequency range 211-275 GHz and 800-950 GHz with double sideband (DSB) noise temperature of about 25 K and 220 K, respectively. The latest results on development, fabrication techniques and experimental study of the SIS receivers will be discussed.

International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)•Nov 8, 2020•7 citations
In recent years, responding to the need of the astronomical community, superconductor - insulator - superconductor (SIS) mixers have been developed to operate at THz frequencies. Best results are obtained by using niobium-based tunnel junctions with well-matched low-loss normal metal striplines, which are found to be less lossy than niobium striplines operated above the gap frequency of niobium (700 GHz). Niobium nitride tunnel junctions with a magnesium oxide tunnel barrier, although having reasonable-quality current - voltage characteristics, have been found to be unsuitable owing to excess shot noise resulting from pinholes in the barrier.
The need for extremely sensitive heterodyne receivers in the astronomical community has created strong efforts to develop appropriate frequency mixers. Nb/Al-Al x O y -Nb tunnel junctions with Nb matching circuits lead to best results up to approximately 700 GHz, the energy-gap frequency of Nb. For higher frequencies the Nb in the matching circuit becomes lossy and is replaced beyond 800 GHz by Al (which operates in the normal conducting state). The gap frequency of NbN is as high as 1.2 THz, but NbN technology is not yet mature. Practical films still have substantial radio frequency losses and the barrier of NbN tunnel junctions is too leaky. More recently, NbTiN, for which the gap frequency is also about 1.2 THz, was found to have very low losses, and is therefore a good choice for tuning circuits. New interesting tunnel junctions for mixers around 1 THz are NbTiN-MgO-NbTiN and Nb/Al-AlN x -NbTiN. Excellent performance from about 1 THz up to several terahertz can be expected from hot-electron transition-edge bolometer mixers. They consist of NbN or Nb microbridges, they do not need matching circuits and their frequency limit is not determined by the gap frequency.
SIS heterodyne mixer technology based on niobium tunnel junctions has now been pushed to frequencies over 1 THz, clearly demonstrating that the SIS junctions are capable of mixing at frequencies up to twice the energy gap frequency (4(Delta) /h). However, the performance degrades rapidly above the gap frequency of niobium (2(Delta) /h approximately equals 700 GHz) due to substantial ohmic losses in the on-chip tuning circuit. To solve this problem, the tuning circuit should be fabricated using a superconducting film with a larger energy gap, such as NbN; unfortunately, NbN films often have a substantial excess surface resistance in the submillimeter band. In contrast, the SIS mixer measurements we present in this paper indicate that the losses for NbTiN thin films can be quite low.
Nb-based superconductor - insulator - superconductor (SIS) mixers with Nb tuning circuits have demonstrated good results up to the Nb gap frequency. Above the gap frequency the performance is expected to degrade quickly because RF loss in Nb becomes significant. In this paper we present the results of an effort to extend Nb-based SIS mixers to THz frequencies by employing lower-loss normal-metal Al wiring and tuning structures. The SIS mixer has two Nb/Al-oxide/Nb junctions connected by an Al microstrip inductor. The direct detection response of the device was measured by a Fourier transform spectrometer. A double-side-band receiver noise temperature of 840 K was obtained at 1042 GHz when the device was operated at 2.5 K.
This thesis describes the development of low-noise heterodyne receivers at THz frequencies for submillimeter astronomy using Nb-based superconductor-insulator-superconductor (SIS) tunneling junctions. The mixers utilize a quasi-optical configuration which consists of a planar twin-slot antenna and antisymmetrically-fed two-junctions on an antireflection-coated silicon hyperhemispherical lens. On-chip integrated tuning circuits, in the form of microstrip lines, are used to obtain maximum coupling efficiency in the designed frequency band. To reduce the rf losses in the integrated tuning circuits above the superconducting Nb gap frequency (~ 700 GHz), normal-metal Al is used to replace Nb as the tuning circuits. To account the rf losses in the micros trip lines, we calculated the surface impedance of the AI films using the nonlocal anomalous skin effect for finite thickness films. Nb films were calculated using the Mattis-Bardeen theory in the extreme anomalous limit. Our calculations show that the losses of the Al and Nb microstrip lines are about equal at 830 GHz. For Al-wiring and Nb-wiring mixers both optimized at 1050 GHz, the RF coupling efficiency of Al-wiring mixer is higher than that of Nb-wiring one by almost 50%. We have designed both Nb-wiring and Al-wiring mixers below and above the gap frequency. A Fourier transform spectrometer (FTS) has been constructed especially for the study of the frequency response of SIS receivers. This FTS features large aperture size (10 inch) and high frequency resolution (114 MHz). The FTS spectra, obtained using the SIS receivers as direct detectors on the FTS, agree quite well with our theoretical simulations. We have also, for the first time, measured the FTS heterodyne response of an SIS mixer at sufficiently high resolution to resolve the LO and the sidebands. Heterodyne measurements of our SIS receivers with Nb-wiring or Al-wiring have yielded results which arc among the best reported to date for broadband heterodyne receivers. The Nb-wiring mixers, covering 400 - 850 GHz band with four separate fixed-tuned mixers, have uncorrected DSB receiver noise temperature around 5hv/kb to 700 GHz, and better than 540 K at 808 GHz. An Al-wiring mixer designed for 1050 GHz band has an uncorrected DSB receiver noise temperature 840 K at 1042 GHz and 2.5 K bath temperature. Mixer performance analysis shows that Nb junctions can work well up to twice the gap frequency and the major cause of loss above the gap frequency is the rf losses in the microstrip tuning structures. Further advances in THz SIS mixers may be possible using circuits fabricated with higher-gap superconductors such as NbN. However, this will require high-quality films with low RF surface resistance at THz frequencies.
We describe a 1 THz quasioptical SIS mixer which uses a twin-slot antenna, an antireflection-coated silicon hyperhemispherical lens, Nb/Al-oxide/Nb tunnel junctions, and an aluminum normal-metal tuning circuit in a two-junction configuration. Since the mixer operates substantially above the gap frequency of niobium (ν≳2Δ/h∼700 GHz), a normal metal is used in the tuning circuit in place of niobium to reduce the Ohmic loss. The frequency response of the device was measured using a Fourier transform spectrometer and agrees reasonably well with the theoretical prediction. At 1042 GHz, the uncorrected double-sideband receiver noise temperature is 840 K when the physical temperature of the mixer is 2.5 K. This is the first SIS mixer which outperforms GaAs Schottky diode mixers by a large margin at 1 THz.
This repost describes our results on development of low-noise heterodyne THz receivers for ground based and space radio astronomy. Superconductor-insulator-superconductor (SIS) mixers that employ high quality Nb-based tunnel junctions are the key element of the most sensitive heterodyne THz receivers. In particular we present here the SIS receivers for frequency range 211-275 GHz and 800-950 GHz with double sideband (DSB) noise temperature of about 25 K and 220 K, respectively. The latest results on development, fabrication techniques and experimental study of the SIS receivers will be discussed.