Superconducting quantum detectors

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A 650 GHz Unilateral Finline SIS Mixer Fed by a Multiple Flare-Angle Smooth-Walled Horn

IEEE Transactions on Terahertz Science and Technology Institute of Electrical and Electronics Engineers (IEEE) 2:1 (2012) 40-49

Authors:

Boon-Kok Tan, Ghassan Yassin, Paul Grimes, Jamie Leech, Karl Jacobs, Christopher Groppi
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A High Performance 700 GHz Feed Horn

Journal of Infrared, Millimeter, and Terahertz Waves Springer Nature 33:1 (2012) 1-5

Authors:

Boon-Kok Tan, Jamie Leech, Ghassan Yassin, Phichet Kittara, Mike Tacon, Sujint Wangsuya, Christopher Groppi
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Experimental Investigation of a Low-Cost, High Performance Focal-Plane Horn Array

IEEE Transactions on Terahertz Science and Technology Institute of Electrical and Electronics Engineers (IEEE) 2:1 (2012) 61-70

Authors:

Jamie Leech, Boon Kok Tan, Ghassan Yassin, Phichet Kittara, Sujint Wangsuya
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Josephson pair tunnelling influence on the performance of an SIS mixer near its superconducting gap

International Journal of Terahertz Science and Technology Terahertz Science and Technology 4:3 (2011) 123-127

Authors:

Boon Tan, G Yassin

Abstract:

We report the investigation of the influence of Josephson pair tunnelling on the sensitivity of an SIS mixer near the superconducting gap of niobium. Hot and cold load measurements were carried out from 600 GHz to 700 GHz, without completely supressing the Josephson effect. We have noticed that when measurements were made at bias points near the first Shapiro step, significantly higher values of Y-factor could be obtained with magnetic field strengths that made the Shapiro step sharper, rather then those that supressed the step. This resulted in a significant improvement in noise temperature of the mixer at those bias points. This observation is important for SIS mixers operating at frequencies near or above gap frequency (ωgap) because the warping of the second negative photon step to the positive display side, narrowing down the bias voltage interval in which measurement of the Y-factor at the first photon step could be done.
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The influence of Josephson Pair Tunnelling on the Sensitivity of an SIS mixer Near the Superconducting Gap

4th UK/Europe Chine Workshop on Millimetre Waves and Terahertz Technologies University of Strathclyde (2011)

Authors:

Boon Tan, G Yassin

Abstract:

We report the investigation of the influence of Josephson pair tunnelling on the sensitivity of an SIS mixer near the superconducting gap of niobium. Hot and cold load measurements were carried out from 600 GHz to 700 GHz, without completely supressing the Josephson effect. We have noticed that when measurements were made at bias points near the first Shapiro step, significantly higher values of Y-factor could be obtained with magnetic field strengths that made the Shapiro step sharper, rather then those that supressed the step. This resulted in a significant improvement in noise temperature of the mixer at those bias points. This observation is important for SIS mixers operating at frequencies near or above gap frequency (ωgap) because the warping of the second negative photon step to the positive display side, narrowing down the bias voltage interval in which measurement of the Y-factor at the first photon step could be done.

Details from ORA