Optical response of a cold-electron bolometer array

A multielement bolometric receiver system has been developed to measure the power and polarization of radiation at a calculated frequency of 345 GHz. Arrays of ten series-parallel connected cold-electron bolometers have been pairwise integrated into orthogonal ports of a cross-slot antenna. Arrays are connected in parallel in the high-frequency input signal and in series in the output signal, which is measured at a low frequency, and in a dc bias. Such an array makes it possible to increase the output resistance by two orders of magnitude as compared to an individual bolometer under the same conditions of high-frequency matching and to optimize the matching with the JFET amplifier impedance up to dozens of megohms. Parallel connection ensures matching of the input signal to the cross-slot antenna with an impedance of 30 Ω on a massive silicon dielectric lens. At a temperature of 100 mK, a response to the thermal radiation of a thermal radiation source with an emissivity of 0.3, which covers the input aperture of the antenna and is heated to 3 K, is 25 μV/K. Taking into account real noise, the optical fluctuation dc sensitivity is 5 mK, the estimated sensitivity corresponding to the noise of the amplifier is about 10⁻⁴ K/Hz^1/2, and the noise-equivalent power is about (1–5) × 10⁻¹⁷ W/Hz^1/2.     

Low-noise wide-band hot-electron bolometer mixer based on an NbN film

We develop and study a hot-electron bolometer mixer made of a two-layer NbN–Au film in situ deposited on a silicon substrate. The double-sideband noise temperature of the mixer is 750K at a frequency of 2.5 THz. The conversion efficiency measurements show that at the superconducting transition temperature, the intermediate-frequency bandwidth amounts to about 6.5GHz for a mixer 0.112 μm long. These record-breaking characteristics are attributed to the improved contacts between a sensitive element and a helical antenna and are reached due to using the in situ deposition of NbN and Au layers at certain stages of the process.     

Carbon nanotube based bolometer

The contacts of single carbon nanotubes and bundles of carbon nanotubes with superconducting and metallic electrodes are investigated in order to create bolometers and electron coolers. Tunneling contacts of the carbon nanotubes with aluminum electrodes are obtained. The current-voltage characteristics of junctions are analyzed for temperatures from room temperature to 300 mK. The resistance of individual nanotubes is primarily determined by defects and is too large for applications. The use of the bundles of carbon nanotubes makes it possible to considerably reduce the resistance of the bolometer, which is determined by a small number of conducting tubes with good tunneling contacts with the electrodes. The energy gap is equal to hundreds and tens of millivolt in the former and latter cases, respectively. Structures containing bundles of carbon nanotubes can be described in a model with a Schottky barrier. The samples with bundles of carbon nanotubes exhibit the bolometric response to external high-frequency radiation at a frequency of 110 GHz with an amplitude up to 100 μV and a temperature voltage response to 0.4 mV/K.     

THz/sub-THz bolometer based on electron heating in a semiconductor waveguide

Direct detection THz/sub-THz bolometer is proposed. In it an electromagnetic wave propagates in the bipolar semiconductor waveguide, heats electrons and holes there, and therefore creates their bipolar thermodiffusion flow and, as well as, the electromotive force (emf). The flow causes the carrier excess concentration. Both this concentration and emf are used to get the bolometer response voltage. The bolometer theoretical model is developed. The possibility without cooling or moderate cooling (about 100 K for the Cd_0.2Hg_0.8Te bolometers) to get acceptable for applications values of the noise equivalent power is shown. Experimental results confirm the main model conclusions.     

Terahertz heterodyne receivers based on superconductive hot-electron bolometer mixers

We consider recent results in development of hot-electron bolometer mixers. Special attention is paid to optimization of the contacts between the antenna and the active area of a superconducting film. An important result in the study of the parasitic effect of direct detection is obtained during the measurement of the noise temperatures by the hot/cold load method. The latest results of studies of the waveguide hot-electron bolometer mixers and their successful practical applications are considered. Progress in development of high-frequency (over 1.3 THz) heterodyne receivers for several important international projects is discussed and new submillimeter radio astronomy projects ESPRIT and SAFIR are described.     

Microwave photonics reconfigurable mixer based on polarization modulator

A reconfigurable and stable mixer is proposed and demonstrated in this paper. It mainly consists of a dual-driven Mach–Zehnder modulator and a polarization modulator with several polarization controllers (PC) and polarizers (Pol). According to the theoretical analysis, different functions (such as single ended mixer, balanced mixer, I/Q mixer and image rejection mixer) can be realized by adjusting the PCs and Pols. The simulation results verify the possibility of multi-functions that realized by the reconfigurable mixer. In addition, another research on how the non-ideal parameters affect the image rejection ratio (ISR) and conversion efficiency of the mixer is also carried. The results show that both of them perform better as the extinction ratio gets higher. However, they are incurring a sharp decrease if the DC bias points deviate from the settled values. In the meantime, the results also indicate that the higher modulation indices lead to a better ISR. A 57.12 dB ISR can be achieved with conversion efficiency of ? 9.53 dB.     

Infrared dipole-coupled bolometer response on a hemispherical silicon immersion lens

Response of an infrared (λ = 10.6 μm) dipole antenna-coupled bolometer fabricated at the center of the flat side of a hemispherical silicon immersion lens is presented. Predicted and measured antenna patterns as well as the ratio of power from the lens-side to the air-side are provided as a function of illumination F/#. The power-division ratio, Φ_lens/Φ_air, is shown to be given by the square root of the lens dielectric constant, ${?}_{\text{Si}}^{1/2}=3.4$, for F/# larger than F/2 whereas as F/# decreases to F/1 the ratio increases to 5 due to off-axis features in the radiation pattern.     

Electron cooling in a normal-metal hot-electron bolometer

Normal-metal hot-electron bolometers, each of which contains two superconductor-insulator-normal metal (SIN) junctions for electron cooling and two SIN junctions for temperature measurements, were fabricated and experimentally studied. The electron cooling by SIN junctions is an analog of the Peltier effect and allows one to reduce the effective electron temperature of a bolometer. The electron temperature was determined from the ratio of the differential resistance to normal one for several values of a constant bias. At a phonon temperature of 250 mK, the resistance ratio at zero bias reached 1000, which was close to the theoretical value for an ideal SIN junction. A decrease in the electron temperature from 250 to 90 mK was obtained.     

基于二极管精确电路模型的183GHz分谐波混频器设计

针对亚毫米波混频二极管管对电路模型不够精确的问题,采用场路结合协同分析,将进出二极管的频率信号分类处理,建立了一种应用于亚毫米波分谐波混频器电路的反向并联二极管对精确电路模型。基于获取的管对精确电路模型,建立了全局性的分谐波混频器电路的集总元件等效电路模型,设计并实现了一款183GHz分谐波混频器。测试结果表明混频器在本振频率为92GHz、功率为2mW,射频频率176~192GHz范围内,双边带变频损耗小于6.8dB,等效噪声温度小于800K,在182GHz测得最小双边带变频损耗为4.9dB,与仿真数据吻合较好。     

A simple image-reject mixer based on two parallel phase modulators

A simple photonic microwave image-reject mixer (IRM) using two parallel phase modulators is proposed. First, a photonic microwave mixer with phase shift ability is achieved using two parallel phase modulators (PMs), an optical bandpass filter, three polarization controllers, three polarization beam splitters and two balanced photodetectors. At the output of the mixer, two frequency downconverted signals with tunable frequency difference can be obtained. By adjusting the phase difference as 90° and utilizing an electrical 90° hybrid, the useless components can be eliminated, and the image reject operation is realized. The key advantage of the proposed scheme is the usage of PM, which avoid the DC bias shifting problem and make the system simple and stable. A simulation is performed to verify the proposed scheme, a relative ??90° or 90° phase shift can be obtained between the two output ports of the photonic microwave mixer, at the output of the IRM, 60 dB image-reject ratio is obtained.     

Terahertz spectroscopy with a Josephson oscillator and a SINIS bolometer

The voltage response of a thin-film normal-metal hot-electron bolometer based on a SINIS (superconductor-insulator-normal metal-insulator-superconductor) structure to the radiation of a high-temperature Josephson junction in the terahertz frequency region was measured. Bolometers were integrated with planar log-periodic and double-dipole antennas, and Josephson junctions were integrated with log-periodic antennas. Measurements showed that the Josephson junction at a temperature of 260 mK was overheated by the transport current, so that its electron temperature exceeded 3 K at a bias voltage of 1 mV. The maximum response of a bolometer with a double-dipole antenna was observed at a frequency of 300 GHz, which agreed well with the calculated value. The Josephson radiation was observed at frequencies up to 1.7 THz. The voltage response of a bolometer reached 4×10⁸ V/W, and the total noise-equivalent power reached 1.5×10^?17 W/Hz^1/2.     

基于二极管精确电路模型的183 GHz分谐波混频器设计

针对亚毫米波混频二极管管对电路模型不够精确的问题,采用场路结合协同分析,将进出二极管的频率信号分类处理,建立了一种应用于亚毫米波分谐波混频器电路的反向并联二极管对精确电路模型。基于获取的管对精确电路模型,建立了全局性的分谐波混频器电路的集总元件等效电路模型,设计并实现了一款183 GHz分谐波混频器。测试结果表明混频器在本振频率为92 GHz、功率为2 mW,射频频率176～192 GHz范围内,双边带变频损耗小于6.8 dB,等效噪声温度小于800 K,在182 GHz测得最小双边带变频损耗为4.9 dB,与仿真数据吻合较好。     

超导HEB的I-V特性模拟

超导热电子测热辐射仪(Superconducting Hot-electron Bolom eter,HEB)是一种检测器件,可以对1THz以上的电磁辐射进行高灵敏度的检测。该工作是利用双温模型,假设电子和声子各自处在平衡态,但具有不同的温度,根据热平衡原理,计算出电子和声子温度在HEB桥上的分布,得到桥两端的电压值,从而得出器件的I-V特性。分析了实验环境温度,转变宽度和薄膜厚度对器件I-V的要求,并与实验测量的结果相比较,为进一步研究超导HEB的混频特性打下基础。     

Experimental study of a normal-metal hot electron bolometer with capacitive coupling

Normal-metal hot-electron bolometer with capacitive coupling (CCNHEB) is a further development of the concept of a normal-metal hot-electron bolometer with Andreev mirrors (ANHEB). It was proposed to eliminate the frequency and energy restrictions inherent in ANHEB, in which Andreev mirrors act efficiently only with relatively long absorbers and at energies below the superconducting gap. An important advantage of the CCNHEB is its simple topology, in which the same tunnel junctions provide thermal decoupling, noise protection, temperature measurement, and it can be used for electron cooling. The temperature response of the bolometer was measured at temperatures down to 260 mK. The observed response dV/dT=1.7mV/K corresponds to the sensitivity S=0.4×10⁹V/W. The measured noise at the amplifier output with this sample was found to be V _na =4nV/Hz^1/2, which corresponds to a noise-equivalent power of 10^?17W/Hz^1/2. To measure optical response, black-body radiation was used as a source of signal inside the cryostat. The source was a thin NiCr film sputtered on a thin sapphire substrate and suspended by nylon threads. Optical measurements proved to be in good agreement with the dc measurements.     

Analysys of the concept of a superconducing bolometer with rf readout

The concept of a superconducting transition-edge bolometer with rf readout, which was proposed in a number of earlier publications, is analyzed. It is shown that such a device cannot in fact operate at the edge of the superconducting transition, and nonequilibrium effects in the superconductor play the major role in its response to the electromagnetic action. A mathematical model is developed, which explains qualitatively the experimental results reported earlier and indicating an unstable response to the action of a readout (pump) signal. The possibility of obtaining a stable response with an optimal choice of parameters of the device is also demonstrated.     

HL-2M 等离子体辐射量热计系统的研制

HL-2M 装置辐射量热计系统采用 16 通道光电二极管阵列作为探测器,11 个探测器阵列,共有 176 个探测通道,被设计在同一个小截面内,交叉覆盖上下偏滤器、等离子体边缘和等离子体芯部区域。数值模拟结 果显示,根据这种视线布局能够精确地估算出等离子体的总辐射功率;运用相关层析反演方法能够重建出等离子 体辐射功率密度的分布特征。在 HL-2M 初始等离子体放电中,根据中平面的探测器阵列对等离子体辐射特征进 行了初步的实验分析。     

Propagation of ballistic phonons in crystals and their detection with a detachable bolometer

Ballistic phonons were generated in single-crystalline sapphire samples by scanning the crystal surface with the electron beam in a scanning electron microscope equipped with a low-temperature stage. The phonons were detected using a superconducting thin film (granular Al) bolometer configuration which could be detached from the sample crystal (allowing repeated use). We have applied these experimental techniques for obtaining phonon images of laser-drilled holes in the sample crystals, achieving a spatial resolution of better than 10 m.     

Submillimeter-wave receiver with a balanced monolithic mixer

We describe the design of a superheterodyne receiver with a balanced monolithic integrated mixer and describe the technique and results of parameter measurements of the receiver and mixer over the frequency range 287–365 GHz. In the middle of this range, the double-band noise temperature of the receiver is 1500±50 K, while the double-band noise temperature and conversion loss of the mixer are 1250±50 K and 10±0.5 dB, respectively. Comparison with mixers and receivers of other types is performed. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 6, pp. 573–580, February 1999.