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Kroug, M., Yagoubov, P., Gol'tsman, G., & Kollberg, E. (1997). NbN quasioptical phonon cooled hot electron bolometric mixers at THz frequencies. In Inst. Phys. Conf. Ser. (Vol. 1, pp. 405–408). Bristol.
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Gerecht, E., Musante, C. F., Wang, Z., Yngvesson, K. S., Waldman, J., Gol'tsman, G. N., et al. (1997). NbN hot electron bolometric mixer for 2.5 THz: the phonon cooled version. In Proc. 8th Int. Symp. Space Terahertz Technol. (pp. 258–271).
Abstract: We describe an investigation of a NbN HEB mixer for 2.5 THz. NbN HEBs are phonon-cooled de-. vices which are expected, according to theory, to achieve up to 10 GHz IF conversion gain bandwidth. We have developed an antenna coupled device using a log-periodic antenna and a silicon lens. We have demon- strated that sufficient LO power can be coupled to the device in order to bring it to the optimum mixer oper- ating point. The LO power required is less than 1 microwatts as measured directly at the device. We also describe the impedance characteristics of NbN devices and compare them with theory. The experimental results agree with theory except for the imaginary part of the impedance at very low frequencies as was demonstrated by other groups.
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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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Cherednichenko, S., Yagoubov, P., Il'In, K., Gol'tsman, G., & Gershenzon, E. (1997). Large bandwidth of NbN phonon-cooled hot-electron bolometer mixers on sapphire substrates. In Proc. 8th Int. Symp. Space Terahertz Technol. (pp. 245–257).
Abstract: The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 mm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 1.1 wide and 211 long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.5 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature.
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Cherednichenko, S., Yagoubov, P., Il'in, K., Gol'tsman, G., & Gershenzon, E. (1997). Large bandwidth of NbN phonon-cooled hot-electron bolometer mixers. In Proc. 27th Eur. Microwave Conf. (Vol. 2, pp. 972–977). IEEE.
Abstract: The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 nm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 um wide and 2 um long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.2 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature.
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Boreman, G. D. (1997). Infrared microantennas. SPIE, 3110, 882–885.
Abstract: We present results of mesurments of the polarization response of asymetric spiral antennas coupled Ni-NiO-Ni diodes, over the wavelength range 10.2 to 10.7 μm. The feed structure of the antenna imposes an elliptical polarization singature that is different from the circular polarization expected from a symmetric spiral. We develop a lossy-transmission-line model yielding the measured polarization response. A combination of a balanced and an unbalanced mode is required. Reflected current waves from the arm ends are significant.
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Semenov, A. D., Heusinger, M. A., Renk, K. F., Menschikov, E., Sergeev, A. V., Elant'ev, A. I., et al. (1997). Influence of phonon trapping on the performance of NbN kinetic inductance detectors. IEEE Trans. Appl. Supercond., 7(2), 3083–3086.
Abstract: Voltage and microwave photoresponse of NbN thin films to modulated and pulsed optical radiation reveals, far below the superconducting transition, a response time consistent with the lifetime of nonequilibrium quasiparticles. We show that even in 5 nm thick films at 4.2 K the phonon trapping is significant resulting in a quasiparticle lifetime of a few nanoseconds that is an order of magnitude larger than the recombination time. Values and temperature dependence of the quasiparticle lifetime obey the Bardeen-Cooper-Schrieffer theory and are in quantitative agreement with the electron-phonon relaxation rate determined from the resistive response near the superconducting transition. We discuss a positive effect of the phonon trapping on the performance of kinetic inductance detectors.
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Verevkin, A. A., Ptitsina, N. G., Smirnov, K. V., Gol'tsman, G. N., Voronov, B. M., Gershenzon, E. M., et al. (1997). Hot electron bolometer detectors and mixers based on a superconducting-two-dimensional electron gas-superconductor structure. In Proc. 4-th Int. Semicond. Device Research Symp. (pp. 163–166).
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Ekstörm, H., Kollberg, E., Yagoubov, P., Gol'tsman, G., Gershenzon, E., & Yngvesson, S. (1997). Gain and noise bandwidth of NbN hot-electron bolometric mixers. Appl. Phys. Lett., 70(24), 3296–3298.
Abstract: We have measured the noise performance and gain bandwidth of 35 Å thin NbN hot-electron mixers integrated with spiral antennas on silicon substrate lenses at 620 GHz. The best double-sideband receiver noise temperature is less than 1300 K with a 3 dB bandwidth of ≈5 GHz. The gain bandwidth is 3.2 GHz. The mixer output noise dominated by thermal fluctuations is 50 K, and the intrinsic conversion gain is about −12 dB. Without mismatch losses and excluding the loss from the beamsplitter, we expect to achieve a receiver noise temperature of less than 700 K.
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Zorin, M., Milostnaya, I., Gol'tsman, G. N., & Gershenzon, E. M. (1997). Fast NbN superconducting switch controlled by optical radiation. IEEE Trans. Appl. Supercond., 7(2), 3734–3737.
Abstract: The switching time and the optical control power of the NbN superconducting switch have been measured. The device is based on the ultrathin film 5-8 nm thick patterned as a structure of several narrow parallel strips (/spl sim/1 /spl mu/m wide) connected to wide current leads. The current-voltage characteristic of the switch at temperature 4.2 K demonstrated a hysteresis due to DC current self-heating. We studied the superconducting-to-resistive state transition induced by both optical and bias-current excitations. The optical pulse duration was /spl sim/20 ps and the rise time of the current step was determined to be less than 50 ps. The optical pulse was delivered to the switch by the semiconductor laser through an optical fiber. We found that the measured switching time is less than the duration of the optical excitation. The threshold optical power density does not exceed 3/spl middot/10/sup 3/ W/cm/sup 2/. The proposed device can be used in the fiber input of LTS rapid single flux quantum circuits.
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