Softwaretechnik-Trends

Aluminum Sub-Micron Superconducting Hot-Electron Bolometer Mixer

Irfan A. Siddiqi, A. Verevkin, D. E. Prober, Anders J. Skalare, Boris S. Karasik, William R. McGrath, P. M. Echternach, Henry George LeDuc

Published May 1, 2000• 3 citations

OpenAlex

Abstract

We report on microwave measurements of superconducting aluminum hot-electron bolometers (Al HEBs). Diffusion-cooled Al HEB mixers are ideal candidates for space-borne and terrestrial remote-sensing applications in the Terahertz frequency range since they are predicted to have small local oscillator (LO) power requirements, intermediate frequency (IF) bandwidths ! 10 GHz, and a noise temperature lower than that of Nb and NbN HEBs. Mixer measurements were made at an LO frequency ~30 GHz LO, with an IF in the range 0.1-7.3 GHz. For T < 0.8 K, a magnetic field H=0.1-0.3T was applied to suppress the superconductivity in the contact pads, and partly in the bridge. For a 0.6 μm long Al HEB, we measure an IF bandwidth of 4 GHz, a conversion efficiency η = -8dB, and a mixer noise temperature Tm ! 4K, DSB (Tmixer=Toutput noise/2η). These results are shown to be in quantitative agreement with simple theoretical predictions.

Related papers

Noise and conversion efficiency of aluminum superconducting hot-electron bolometer mixer

Irfan A. Siddiqi, A. Verevkin, D. E. Prober +5 more

We report on microwave measurements of superconducting aluminum hot-electron bolometers (Al HEBs). Diffusion-cooled Al HEB mixers are good candidates for space-borne applications in the Terahertz frequency range since they are predicted to have small local oscillator (LO) power requirements, intermediate frequency (IF) bandwidths /spl gsim/10 GHz, and a noise temperature lower than that of Nb and NbN HEB mixers. Mixer measurements were made at an LO frequency /spl sim/30 GHz, with an IF in the range 0.1 to 7.3 GHz. For T<0.8 K, a magnetic field H=0.1-0.3 T was applied to suppress the superconductivity in the contact pads, and partly in the bridge. For a 0.6 /spl mu/m long device, we measure an IF bandwidth of 4 GHz, a conversion efficiency /spl eta/=-8 dB, and a mixer noise temperature T/sub M//spl gsim/4 K, DSB (T/sub mixer/=T/sub output noise//2/spl eta/). These results are shown to be in quantitative agreement with simple theoretical predictions.

IEEE Transactions on Applied SuperconductivityMar 1, 200117 citations

Aluminum hot-electron bolometer mixers at submillimeter wavelengths

Anders J. Skalare, William R. McGrath, P. M. Echternach +4 more

Diffusion-cooled aluminum hot-electron bolometer (HEB) mixers are of interest for low-noise high resolution THz-frequency spectroscopy within astrophysics. Al HEB mixers offer operation with an order of magnitude less local oscillator power, higher intermediate frequency bandwidth and potentially lower noise than competing devices made from other materials. We report on mixer experiments at 618 GHz with devices fabricated from films with sheet resistances in the range from about 55 /spl Omega/ down to about 9 /spl Omega/ per square. Intermediate frequency bandwidths of up to 3 GHz were measured (1 /spl mu/m long device), with absorbed local oscillator power levels of 0.5 to 6 nW and mixer conversion up to -21.5 dB. High input coupling efficiency implies that the electrons in the device are able to thermalize before escaping from the device. It was found that the long coherence length complicates mixer operations due to the proximity of the contact pads. Also, saturation at the IF frequency may be a concern for this type of device, and warrants further studies.

IEEE Transactions on Applied SuperconductivityMar 1, 200117 citations

Heterodyne mixing in diffusion-cooled superconducting aluminum hot-electron bolometers

Irfan A. Siddiqi, A. Verevkin, D. E. Prober +4 more

We present microwave (30 GHz) measurements on aluminum superconducting hot-electron bolometer (HEB) mixers. Aluminum HEB mixers have a lower superconducting transition temperature than niobium and niobium nitride devices, and are predicted to have improved sensitivity and require less local oscillator power. The devices studied consist of a narrow superconducting aluminum microbridge with contacts comprised of thick aluminum, titanium, and gold. A perpendicular magnetic field is used to suppress superconductivity in the contacts. The device length is much shorter than the electron–phonon inelastic length [L≪(Dτe–ph)1/2] and thus the intermediate frequency (IF) bandwidth is set by the diffusion time of hot electrons from the microbridge into the contacts. We discuss limitations on the IF bandwidth in very short HEB mixers with fully normal contacts. Overall, the microwave heterodyne mixing results show good performance with a mixer noise temperature inferred from the conversion efficiency and output noise of TM⩾4 K, double side band (DSB). Measurements at 618 GHz yield a conversion efficiency approximately 10 dB lower than observed at 30 GHz. Output saturation by background radiation is postulated to contribute significantly to this difference. A similar decrease in conversion efficiency in the microwave mixing measurements is observed when broadband noise is added to the rf input signal. We discuss the tradeoff between increased sensitivity and the occurrence of saturation effects in low transition temperature HEBs.

Journal of Applied PhysicsApr 1, 200213 citations

Low-noise and wideband hot-electron superconductive mixer for terahertz frequencies

Boris S. Karasik, Anders J. Skalare, William R. McGrath +7 more

Superconductive hot-electron bolometer (HEB) mixers have been built and tested in the frequency range from 1.1 THz to 2.5 THz. The mixer device is a 0.15 - 0.3 micrometer microbridge made from a 10 nm thick Nb film. This device employs diffusion as a cooling mechanism for hot electrons. The double sideband noise temperature was measured to be less than or equal to 3000 K at 2.5 THz and the mixer IF bandwidth is expected to be at least 10 GHz for a 0.1 micrometer long device. The local oscillator (LO) power dissipated in the HEB microbridge was 20 - 100 nW. Further improvement of the mixer characteristics can be potentially achieved by using Al microbridges. The advantages and parameters of such devices are evaluated. The HEB mixer is a primary candidate for ground based, airborne and spaceborne heterodyne instruments at THz frequencies. HEB receivers are planned for use on the NASA Stratospheric Observatory for Infrared Astronomy (SOFIA) and the ESA Far Infrared and Submillimeter Space Telescope (FIRST). The prospects of a submicron-size YBa2Cu3O7-(delta ) (YBCO) HEB are discussed. The expected LO power of 1 - 10 (mu) W and SSB noise temperature of approximately equals 2000 K may make this mixer attractive for various remote sensing applications.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIENov 13, 19981 citation

Low-noise and wideband hot-electron superconductive mixers for THz frequencies

Boris S. Karasik, Anders J. Skalare, Rolf A. Wyss +5 more

Superconductive hot-electron bolometer (HEB) mixers have been built and tested in the frequency range 1.1-2.5 THz. The mixer device is a 0.15-03 /spl mu/m microbridge made from a 10 nm thick Nb film. This device employs diffusion as a cooling mechanism for hot electrons. The double sideband noise temperature was measured to be /spl les/3000 K at 2.5 THz and the mixer IF bandwidth is /spl ap/9-10 GHz for a 0.1 /spl mu/m long device. The local oscillator (LO) power dissipated in the HEB microbridge was 20-100 nW. Further improvement of the mixer characteristics can be potentially achieved by using Al microbridges. The advantages and parameters of such devices are evaluated The HEB mixer Is a primary candidate for ground based, airborne and spaceborne heterodyne instruments at THz frequencies. HEB receivers are planned for use on the NASA Stratospheric Observatory for Infrared Astronomy (SOFIA) and the ESA Far Infrared and Submillimeter Space Telescope (FIRST). The prospects of a submicron-size YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) HEB are also discussed. The expected LO power of 1-10 /spl mu/W and SSB noise temperature of /spl ap/2000 K may make this mixer attractive for various remote sensing applications.

IEEE International Conference on Terahertz Electronics (THz)Nov 27, 20025 citations

Reduced Tc Niobium superconducting HEB mixers

Henry George LeDuc, B. Bumble, Irfan A. Siddiqi +1 more

A reduction in the mixer noise is expected when using superconductors with a lower transition temperature (Tc) since the thermal noise components of the mixer noise should scale with Tc. Also, the local oscillator (LO) power required for a diffusion-cooled device should decrease as Tc when Tbath<<Tc. We previously studied mixing in aluminum based hot-electron bolometers (HEBs) at microwave frequencies (~30 GHz), and observed a significant improvement in noise performance, and a reduction in LO power as predicted. However, the bias voltage range over which good mixer performance was observed was ~ 5-10 μV. These devices are thus susceptible to saturation effects, in particular output saturation. In the present work, we have investigated Nb HEBs whose Tc is lowered by applying a magnetic field. The goal is to study a case intermediate between Nb and Al, and hopefully to find properties that will allow use in practical receivers. A 15 kOe perpendicular magnetic field was applied to a Nb HEB (L=0.16 μm, W=0.08 μm, RN=90Ω) to reduce Tc from 5.2 K to 2.4 K. The mixer noise, as inferred from the output noise and the conversion efficiency, decreased from 390 K, DSB to 171 K, DSB. The LO power required for near optimum mixer conversion efficiency (ηmixer = 9 dB in this device) was 8nW in zero field, and ~ 2 nW when Tc was reduced to 2.4K. Tbath=0.22K. The conversion bandwidth was previously measured to be 2.4 GHz and the same bandwidth was observed in the presence of a magnetic field. By lowering Tc, the voltage range over which good mixing was observed also decreased. However, even with Tc reduced to 2.4 K, the conversion efficiency dropped by 3dB from its maximum value only when the bias voltage was changed by ~ 90 μV. Saturation effects should thus be much less of a concern in these devices than in Al HEBs. In situations where the application of a large magnetic field is not feasible, we suggest using Ta based HEBs. Ta HEBs should have Tc ~ 3-3.5K and material properties very similar to Nb.

Feb 14, 20010 citations