Meledin, D. V., Marrone, D. P., Tong, C. - Y. E., Gibson, H., Blundell, R., Paine, S. N., et al. (2004). A 1-THz superconducting hot-electron-bolometer receiver for astronomical observations. IEEE Trans. Microwave Theory Techn., 52(10), 2338–2343.
Abstract: In this paper, we describe a superconducting hot-electron-bolometer mixer receiver developed to operate in atmospheric windows between 800-1300 GHz. The receiver uses a waveguide mixer element made of 3-4-nm-thick NbN film deposited over crystalline quartz. This mixer yields double-sideband receiver noise temperatures of 1000 K at around 1.0 THz, and 1600 K at 1.26 THz, at an IF of 3.0 GHz. The receiver was successfully tested in the laboratory using a gas cell as a spectral line test source. It is now in use on the Smithsonian Astrophysical Observatory terahertz test telescope in northern Chile.
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Lindgren, M., Zorin, M. A., Trifonov, V., Danerud, M., Winkler, D., Karasik, B. S., et al. (1994). Optical mixing in a patterned YBa2Cu3O7-δ thin film. Appl. Phys. Lett., 65(26), 3398–3400.
Abstract: Mixing of 1.56 µm infrared radiation from two lasers in a high quality YBa2Cu3O7-δ thin film, patterned to parallel strips, was demonstrated. A mixer bandwidth of 18 GHz, limited by the measurement system, was obtained. A model based on nonequilibrium electron heating gives a good fit to the data and predicts an intrinsic mixer bandwidth in excess of 100 GHz, operating in the whole infrared spectrum. Reduction of bolometric effects and ways to decrease the conversion loss of the mixer is discussed. The minimum conversion loss is expected to be ~10 dB.
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Karasik, B. S., & Elantiev, A. I. (1996). Noise temperature limit of a superconducting hot-electron bolometer mixer. Appl. Phys. Lett., 68(6), 853–855.
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Karasik, B. S., Il'in, K. S., Pechen, E. V., & Krasnosvobodtsev, S. I. (1996). Diffusion cooling mechanism in a hot-electron NbC microbolometer mixer. Appl. Phys. Lett., 68(16), 2285–2287.
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Floet, D. W., Baselmans, J. J. A., Klapwijk, T. M., & Gao, J. R. (1998). Resistive transition of niobium superconducting hot-electron bolometer mixers. Appl. Phys. Lett., 73(19), 2826.
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Fu, K., Zannoni, R., Chan, C., Adams, S. H., Nicholson, J., Polizzi, E., et al. (2008). Terahertz detection in single wall carbon nanotubes. Appl. Phys. Lett., 92(3), 033105.
Abstract: It is reported that terahertz radiation from 0.69 to 2.54 THz has been sensitively detected in a device consisting of bundles of carbon nanotubes containing single wall metallic carbon nanotubes, quasioptically coupled through a lithographically fabricated antenna, and a silicon lens. The measured data are consistent with a bolometric detection process in the metallic tubes and the devices show promise for operation well above 4.2 K.
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Siddiqi, I., & Prober, D. E. (2004). Nb–Au bilayer hot-electron bolometers for low-noise THz heterodyne detection. Appl. Phys. Lett., 84(8), 1404.
Abstract: The sensitivity of present Nb diffusion-cooled hot-electron bolometer (HEB) mixers is not quantum limited, and can be improved by reducing the superconducting transition temperature TC. Lowering TC reduces thermal fluctuations, resulting in a decrease of the mixer noise temperature TM. However, lower TC mixers have reduced dynamic range and saturate more easily due to background noise. We present 30 GHz microwave measurements on a bilayer HEB system, Nb–Au, in which TC can be tuned with Au layer thickness to obtain the maximum sensitivity for a given noise background. These measurements are intended as a guide for the optimization of THz mixers. Using a Nb–Au mixer with TC = 1.6 K, we obtain TM = 50 K with 2 nW of local oscillator (LO) power. Good mixer performance is observed over a wide range of LO power and bias voltage and such a device should not exhibit saturation in a THz receiver.
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Il'in, K. S., Lindgren, M., Currie, M. A., Semenov, D., Gol'tsman, G. N., Sobolewski, R., et al. (2000). Picosecond hot-electron energy relaxation in NbN superconducting photodetectors. Appl. Phys. Lett., 76(19), 2752–2754.
Abstract: We report time-resolved characterization of superconducting NbN hot-electron photodetectors using an electro-optic sampling method. Our samples were patterned into micron-size microbridges from 3.5-nm-thick NbN films deposited on sapphire substrates. The devices were illuminated with 100 fs optical pulses, and the photoresponse was measured in the ambient temperature range between 2.15 and 10.6 K (superconducting temperature transition TC). The experimental data agreed very well with the nonequilibrium hot-electron, two-temperature model. The quasiparticle thermalization time was ambient temperature independent and was measured to be 6.5 ps. The inelastic electron–phonon scattering time Ï„e–ph tended to decrease with the temperature increase, although its change remained within the experimental error, while the phonon escape time Ï„es decreased almost by a factor of two when the sample was put in direct contact with superfluid helium. Specifically, Ï„e–ph and Ï„es, fitted by the two-temperature model, were equal to 11.6 and 21 ps at 2.15 K, and 10(±2) and 38 ps at 10.5 K, respectively. The obtained value of Ï„e–ph shows that the maximum intermediate frequency bandwidth of NbN hot-electron phonon-cooled mixers operating at TC can reach 16(+4/–3) GHz if one eliminates the bolometric phonon-heating effect.
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Hübers, H. - W., Semenov, A., Holldack, K., Schade, U., Wüstefeld, G., & Gol’tsman, G. (2005). Time domain analysis of coherent terahertz synchrotron radiation. Appl. Phys. Lett., 87(18), 184103 (1 to 3).
Abstract: The time structure of coherent terahertz synchrotron radiation at the electron storage ring of the Berliner Elektronensynchrotron und Speicherring Gesellschaft has been analyzed with a fast superconducting hot-electron bolometer. The emission from a single bunch of electrons was found to last ∼1500ps at frequencies around 0.4THz, which is much longer than the length of an electron bunch in the time domain (∼5ps). It is suggested that this is caused by multiple reflections at the walls of the beam line. The quadratic increase of the power with the number of electrons in the bunch as predicted for coherent synchrotron radiation and the transition from stable to bursting radiation were determined from a single storage ring fill pattern of bunches with different populations.
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Kawamura, J., Blundell, R., Tong, C. -yu E., Gol’tsman, G., Gershenzon, E., Voronov, B., et al. (1997). Low noise NbN lattice-cooled superconducting hot-electron bolometric mixers at submillimeter wavelengths. Appl. Phys. Lett., 70(12), 1619–1621.
Abstract: Lattice-cooled superconducting hot-electron bolometric mixers are used in a submillimeter-wave waveguide heterodyne receiver. The mixer elements are niobium nitride film with 3.5 nm thickness and ∼10 μm2 area. The local oscillator power for optimal performance is estimated to be 0.5 μW, and the instantaneous bandwidth is 2.2 GHz. At an intermediate frequency centered at 1.4 GHz with 200 MHz bandwidth, the double sideband receiver noise temperature is 410 K at 430 GHz. The receiver has been used to detect molecular line emission in a laboratory gas cell.
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