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Jackson BD, Baryshev AM, de Lange G, Gao JR, Shitov SV, Iosad NN, et al. Low-noise 1 THz superconductor-insulator-superconductor mixer incorporating a NbTiN/SiO2/Al tuning circuit. Appl. Phys. Lett.. 2001;79(3):436.
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Barends R, Hajenius M, Gao JR, Klapwijk TM. Current-induced vortex unbinding in bolometer mixers. Appl Phys Lett. 2005;87:263506 (1 to 3).
Abstract: We present a description of the current-voltage characteristics of hot electron bolometers in terms of the current-dependent intrinsic resistive transition of NbN films. We find that, by including this current dependence, we can correctly predict the complete current-voltage characteristics, showing excellent agreement with measurements for both low and high bias and for small as well as large devices. It is assumed that the current dependence is due to vortex-antivortex unbinding as described in the Berezinskii–Kosterlitz–Thouless theory. The presented approach will be useful in guiding device optimization for noise and bandwidth.
Keywords: HEB mixer numerical model, HEB model, IV-curves, vortex-antivortex, Berezinskii–Kosterlitz–Thouless theory, diffusion cooling channel, diffusion channel, distributed HEB model, distributed model, self-heating effect, temperature profile
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Zhang W, Khosropanah P, Gao JR, Kollberg EL, Yngvesson KS, Bansal T, et al. Quantum noise in a terahertz hot electron bolometer mixer. Appl Phys Lett. 2010;96(11):111113–(1.
Abstract: We have measured the noise temperature of a single, sensitive superconducting NbN hot electron bolometer (HEB) mixer in a frequency range from 1.6 to 5.3 THz, using a setup with all the key components in vacuum. By analyzing the measured receiver noise temperature using a quantum noise (QN) model for HEB mixers, we confirm the effect of QN. The QN is found to be responsible for about half of the receiver noise at the highest frequency in our measurements. The beta-factor (the quantum efficiency of the HEB) obtained experimentally agrees reasonably well with the calculated value.
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Gao JR, Hovenier JN, Yang ZQ, Baselmans JJA, Baryshev A, Hajenius M, et al. Terahertz heterodyne receiver based on a quantum cascade laser and a superconducting bolometer. Appl Phys Lett. 2005;86:244104 (1 to 3).
Abstract: We report the first demonstration of an all solid-stateheterodyne receiver that can be used for high-resolution spectroscopy above 2THz suitable for space-based observatories. The receiver uses a NbN superconducting hot-electron bolometer as mixer and a quantum cascade laser operating at 2.8THz as local oscillator. We measure a double sideband receiver noise temperature of 1400K at 2.8THz and 4.2K, and find that the free-running QCL has sufficient power stability for a practical receiver, demonstrating an unprecedented combination of sensitivity and stability.
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Klapwijk TM, Barends R, Gao JR, Hajenius M, Baselmans JJA. Improved superconducting hot-electron bolometer devices for the THz range. In: Proc. SPIE. Vol 5498.; 2004. p. 129–39.
Abstract: Improved and reproducible heterodyne mixing (noise temperatures of 950 K at 2.5 THz) has been realized with NbN based hot-electron superconducting devices with low contact resistances. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature, has been used to understand the physical conditions during the mixing process. We find that the mixing is predominantly due to the exponential rise of the local resistivity as a function of electron temperature.
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