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Hübers, H. - W., Semenov, A., Schubert, J., Gol'tsman, G., Voronov, B., & Gershenzon, E. (2000). Performance of the phonon-cooled hot-electron bolometric mixer between 0.7 THz and 5.2 THz. In Proc. 8-th Int. Conf. on Terahertz Electronics (pp. 117–119).
Abstract: We report on the phonon cooled NbN hot electron bolometer as mixer in the terahertz frequency range. Its hybrid antenna consists of a hyperhemispheric silicon lens and a logarithmic-spiral feed antenna. Noise temperatures have been measured between 0.7 THz and 5.2 THz. A quarter wavelength layer of Parylene works as antireflection coating for the silicon lens and reduces the noise temperature by about 30. It was found that the antenna pattern at 2.5 THz is determined by the feed antenna and not by the diameter of the lens.
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Semenov, A. D., Gol'tsman, G. N., & Sobolewski, R. (2002). Hot-electron effect in superconductors and its applications for radiation sensors. Supercond. Sci. Technol., 15(4), R1–R16.
Abstract: The paper reviews the main aspects of nonequilibrium hot-electron phenomena in superconductors and various theoretical models developed to describe the hot-electron effect. We discuss implementation of the hot-electron avalanche mechanism in superconducting radiation sensors and present the most successful practical devices, such as terahertz mixers and direct intensity detectors, for far-infrared radiation. Our presentation also includes the novel approach to hot-electron quantum detection implemented in superconducting x-ray to optical photon counters.
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Semenov, A. D., Richter, H., Hubers, H. - W., Gunther, B., Smirnov, A., Il'in, K. S., et al. (2007). Terahertz performance of integrated lens antennas with a hot-electron bolometer. IEEE Trans. Microw. Theory Techn., 55(2), 239–247.
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Semenov, A., Richter, H., Smirnov, K., Voronov, B., Gol'tsman, G., & Hübers, H. - W. (2004). The development of terahertz superconducting hot-electron bolometric mixers. Supercond. Sci. Technol., 17(5), 436–439.
Abstract: We present recent advances in the development of NbN hot-electron bolometric (HEB) mixers for flying terahertz heterodyne receivers. Three important issues have been addressed: the quality of the source NbN films, the effect of the bolometer size on the spectral properties of different planar feed antennas, and the local oscillator (LO) power required for optimal operation of the mixer. Studies of the NbN films with an atomic force microscope indicated a surface structure that may affect the performance of the smallest mixers. Measured spectral gain and noise temperature suggest that at frequencies above 2.5 THz the spiral feed provides better overall performance than the double-slot feed. Direct measurements of the optimal LO power support earlier estimates made in the framework of the uniform mixer model.
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Semenov, A., Il'yin, K., Siegel, M., Smirnov, A., Pavlov, S., Richter, H., et al. (2006). Intermediate frequency bandwidth of a hot-electron mixer: Comparision with bolometric models. In Proc. 17th Int. Symp. Space Terahertz Technol. (pp. 73–76). Paris, France.
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