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A superconducting millimetre switch with multiple nano-bridges

Boon-Kok Tan, G. Yassin, L. S. Kuzmin, Ernst Otto, H. Merabet, Chris E. North

Published Jan 1, 2014• 4 citations
OpenAlex

Abstract

In this paper, we describe the design of a planar superconducting on/off switch comprising a high normal resistance nano-bridge deposited across a slotline transmission line. We present preliminary experimental results measured at 220 GHz range, and we discuss in detail the various parameters that affect the performance of the planar on/off switch, including the optimum thickness required for the nano-bridge to achieve high dynamic range and low transmission loss. The analysis is done by combining the accurate superconducting surface impedance description with rigorous electromagnetic simulations, and comparing the simulated results with the measured performance of a previously fabricated on/off switch fed by a backto- back unilateral finline taper. Finally, we propose an improved method to further increase the dynamic range of the switch, by introducing a multi-bridge design to tune out the residual inductance of the nano-bridges.

Related papers

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We present the design of planar superconducting on/off switch comprising a number of high normal resistance nano-bridges deposited across a the slot of a unilateral finline. We have simulated the performance of this device and have shown that it has a much larger dynamic range than a single nano-bridge fabricated from the same material (Niobium Nitride, NbN). The response of a single bridge device was measured either directly using a terahertz power meter or by using superconductor-insulator-superconductor (SIS) device as direct detector. In either method, we have demonstrated good agreement between simulations and measurements, and therefore confirmed the integrity of our analysis of the device performance. We have recently designed and fabricated multiple nano-bridges superconducting switches using 50m thick NbN film. The measurement of these devices is currently in progress and we expect to report the results in the forthcoming ISSTT conference in March.

ORA review team•Jan 1, 2015•3 citations

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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Jun 14, 2006•6 citations
In this paper, we describe the design of a planar superconducting on/off switch comprising a high normal resistance nano-bridge deposited across a slotline transmission line. We present preliminary experimental results measured at 220 GHz range, and we discuss in detail the various parameters that affect the performance of the planar on/off switch, including the optimum thickness required for the nano-bridge to achieve high dynamic range and low transmission loss. The analysis is done by combining the accurate superconducting surface impedance description with rigorous electromagnetic simulations, and comparing the simulated results with the measured performance of a previously fabricated on/off switch fed by a backto- back unilateral finline taper. Finally, we propose an improved method to further increase the dynamic range of the switch, by introducing a multi-bridge design to tune out the residual inductance of the nano-bridges.
We present the design of planar superconducting on/off switch comprising a number of high normal resistance nano-bridges deposited across a the slot of a unilateral finline. We have simulated the performance of this device and have shown that it has a much larger dynamic range than a single nano-bridge fabricated from the same material (Niobium Nitride, NbN). The response of a single bridge device was measured either directly using a terahertz power meter or by using superconductor-insulator-superconductor (SIS) device as direct detector. In either method, we have demonstrated good agreement between simulations and measurements, and therefore confirmed the integrity of our analysis of the device performance. We have recently designed and fabricated multiple nano-bridges superconducting switches using 50m thick NbN film. The measurement of these devices is currently in progress and we expect to report the results in the forthcoming ISSTT conference in March.
We present preliminary measured responses of a planar superconducting on/off switch centred at the 220 GHz. The superconducting switch, comprising three niobium nitride (NbN) bridges, deposited across the slotline section of a back-to-back unilateral linline, made of a similar superconducting material. The transmission characteristics of the superconducting switch illuminated by a sub-millimetre source were measured using a superconductor-insulator-superconductor (SIS) chip as direct detector. The NbN bridges were switched from the super-conducting state to the normal state by a bias current exceeding the critical current of the bridges. With this arrangement, we have measured a switching dynamic range of ∼ 13 dB at 245 GHz, demonstrating the successful operation of the multiple NbN bridges planar superconducting on/off switch.
We present preliminary measured responses of a planar superconducting on/off switch operating at millimeter wavelengths. The superconducting switch, comprising three niobium nitride (NbN) bridges, is deposited across the slotline section of a back-to-back unilateral finline. The transmission characteristics of the superconducting switch illuminated by a millimeter source was measured using a superconductor-insulator-superconductor (SIS) tunnel junction as direct detector. The NbN bridges were switched from the superconducting state to the normal state by passing current through the bridges with magnitude that exceeds its critical current value. With this arrangement, we have measured a typical switching dynamic range of approximately 10 dB across the 205-240 GHz band, with the highest dynamic range of ~ 20 dB at 230 GHz. This demonstrated the successful operation of the multiple NbN bridges as a planar superconducting on/off switch.
We present the design and some preliminary measured results of a planar superconducting on/off switch comprising two niobium nitride (NbN) bridges deposited across the slotline section of a unilateral finline. The two bridges are separated by a distance of λ/4, such that the superconducting impedance of the bridges could be cancelled out at the resonance frequency. Both the NbN bridges were switched from the superconducting state to the normal state via a bias current exceeding the critical current of the NbN film. A millimetre wave source calibrated with a terahertz power meter is used to illuminate the switch, and the response of the switch in each state was measured using a superconductor-insulator-superconductor (SIS) chip as a direct detector. Preliminary measured results agreed generally well with our simulations, especially when the multiple wave reflection effect is included in our model.
We describe the design and fabrication of a 220 GHz superconductor-insulator-superconductor (SIS) mixer with ultrawide IF bandwidth. The mixer is fabricated on a 100 µm thick quartz substrate, with planar circuit on-chip integration. The RF power is coupled to the tunnel junction via a unilateral finline taper and a slotline-to-microstrip transition. We used a double-stub tuning network to tune out the junction’s parasitic capacitance at a broad RF bandwidth, and matched the output impedance of the mixer to the input impedance of the IF amplifier (50 Ω) from 4–18 GHz using a 6-stage IF impedance-transformer. We have fabricated these devices and have measured good DC current-voltage (IV) characteristic curves. The heterodyne mixing performance of these devices is currently being measured, and we expect to present the results in the forthcoming ISSTT conference in March.
Several technologies are now being considered for modulating the polarization in various B-mode instruments, including rotating quasioptical half-wave plates in front of the focal plane array, rotating waveguide half-wave plates and Faraday rotators. It is not at all clear that any of these techniques is feasible without heavy penalty in cost or performance. A potentially much more efficient method is to use a pseudo-correlation polarimeter in conjunction with a planar circuit phase switch. We investigate three different devices for use as mm-wave switches, SIS tunnel junctions, capacitively coupled superconducting nanostrips and RF MEMS. The SIS tunnel junction switches operate by switching between two different bias voltages, while the nanostrip switch operates by changing the impedance of a resonant circuit by driving the nanostrip from the superconducting to normal state. In each case the RF signal sees two substantially different complex impedance states, hence could be switched from one transmission line branch to another. In MEMS this is achieved by mechanical movement of one plate of a parallel plate capacitor system. Although RF MEMS have been reported at high microwave and low mm-wave frequencies, in this work we have investigated cryogenic MEMS for operation at high mm-wave frequencies (225 GHz) using superconducting transmission lines. We present and compare designs and simulations of the performance of phase switches based on all three switching technologies, as well as preliminary experimental results for each of the switches. Finally we also present designs of phase shift circuits that translates the on/off switching into phase modulation.