Investigation of the Speed of a SINIS Bolometer at a Frequency of 350 GHz

We have measured the time of the optical response of a 350-GHz radiation detector based on a superconductor–insulator–normal metal–insulator–superconductor tunnel structure with a suspended normal-metal bridge integrated into a planar log-periodic antenna. The transient characteristics of the detector were recorded when irradiated by a fast cryogenic blackbody source with a rise time of the order of microseconds. For this purpose, a short intense heating pulse was fed to an emitting NiCr film radiation source with a low heat capacity. The measured response time was 1.8 ± 0.5 μs at a bolometer electron temperature of 0.17 K, with a detection sensitivity of 10^–17–10^–18 W Hz^–1/2 being potentially achievable.     

Temperature sensitivity and noise of an HTSC Josephson detector on a sapphire bicrystal substrate at 77 K

In YBa₂Cu₃O_{7 ? x} films grown on sapphire bicrystal substrates, the Josephson junctions are prepared based on artificial grain boundaries formed by the turn of the crystal lattices about the [100] axis. The films are deposited by the laser ablation method on the buffer CeO₂ layer. The critical film temperature reaches 88.5 K with a transition width of 1.5 K. Junctions from 2 to 3-μ m wide are integrated into the planar log-periodic antennas and their characteristics are measured at 77 K. The characteristic voltage I _c R _n reaches 570 μV. With exposure to external radiation at a frequency of 113 GHz, the Shapiro steps were observed on the current-voltage characteristic. The temperature sensitivity of this detector placed in a quasi-optical receiving unit is measured. At the modulation of the input radiation temperature 77 K/300 K, a response of more than 200 nV is observed at the detector output. At the modulation frequency, intrinsic noise is about 1 nV/Hz^1/2, which corresponds to a temperature resolution of 1 K.     

Monolithic Uncooled 8 × 8 Bolometer Arrays Based on Poly-SiGe Thermistor

This paper presents a monolithic uncooled 8 × 8 bolometer array with polycrystalline silicon-germanium (poly-SiGe) thermistors as active elements. The poly-SiGe films are deposited by ultrahigh vacuum vapor deposition (UHV/CVD) system and the dependence of the temperature coefficient of resistance (TCR) on annealing temperature has been investigated. To decrease the thermal conductance of the bolometer, the poly-SiGe thermistor was formed on a four leg suspended microbridge. The improved porous silicon micromachining techniques described here enable the integration of the bolometer array with the MOS readout circuitry. The measurements and calculations show that the mean responsivity is 1.07 × 10⁴ V/W with an uncorrected uniformity of 10.5% and a thermal response time of 10.5 ms, and the detectivity of 3.75 × 10⁸ cm Hz^1/2/W is achieved at a chopping frequency of 30 Hz and a bias voltage of 5 V.     

Terahertz pulse driven Josephson junctions

The voltage response of a Josephson junction to a pulsed terahertz current is evaluated in the limit of a negligible junction capacitance (overdamped limit). The time-dependent superconductor phase difference across the junction is calculated in the framework of the standard resistive shunted junction model by using a perturbative method. The pulsed current bias affects the time average value of the voltage across the junction and current steps are induced in the current–voltage characteristics for voltage values depending on the pulse repetition rate. The current step height is proportional to the square of the pulse time width (τ) to the period (T) ratio. A fast response detector for pulsed Terahertz radiation is proposed, with an expected responsivity of the order of 0.1 V/W and an equivalent noise power of about 3 × 10^?10 W/Hz^1/2.     

Temperature sensitivity and noise of an HTSC Josephson detector on a sapphire bicrystal substrate at 77 K

In YBa₂Cu₃O_{7 − x} films grown on sapphire bicrystal substrates, the Josephson junctions are prepared based on artificial grain boundaries formed by the turn of the crystal lattices about the [100] axis. The films are deposited by the laser ablation method on the buffer CeO₂ layer. The critical film temperature reaches 88.5 K with a transition width of 1.5 K. Junctions from 2 to 3-μ m wide are integrated into the planar log-periodic antennas and their characteristics are measured at 77 K. The characteristic voltage I _c R _n reaches 570 μV. With exposure to external radiation at a frequency of 113 GHz, the Shapiro steps were observed on the current-voltage characteristic. The temperature sensitivity of this detector placed in a quasi-optical receiving unit is measured. At the modulation of the input radiation temperature 77 K/300 K, a response of more than 200 nV is observed at the detector output. At the modulation frequency, intrinsic noise is about 1 nV/Hz^1/2, which corresponds to a temperature resolution of 1 K. Original Russian Text ? M. Tarasov, E. Stepantsov, A. Kalabukhov, M. Kupriyanov, D. Winkler, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, pp. 828–831.     

Cold-electron bolometer arrays

To improve electron cooling, expand the dynamic range, and match the input and output impedances, series/parallel arrays of cold-electron bolometers have been developed, manufactured, and measured at temperatures from 50 to 350 mK. The bolometers are integrated into cross-slot antennas to analyze the polarization of cosmic microwave background radiation at a frequency of 345 GHz. The maximum temperature response is 6.5 μV/mK. The noise-equivalent electric power at a temperature of 300 mK is 1.2 × 10^?17 W/Hz^1/2.     

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.     

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.     

高Tc超导薄膜约瑟夫逊结光探测研究

我们研制了具有约瑟夫逊效应的高Tc GdBa₂Cu₃O₇-薄膜双晶晶界结,对其交直流约瑟夫逊效应进行了观测,并用其进行光探测,用波长为0.6328μm的He-Ne激光器辐照双晶结结区,系统观测了双晶晶界结的光响应特性,得到的最好结果如下噪音等效功率NEP=1.9×10^-13W,归一化探测率D=53×109cmHz^1/2W^-1,响应率Rv=4.2×10⁷V/W,响应时间τ=4.35×10^-7s.     

Bi-SQUID arrays and parallel SQIF structures for active electrically small antennas

The basic physics of the development of broadband active electrically small superconductive antennas for the subgigahertz and gigahertz frequency ranges, based on series arrays with cells characterized by a highly linear voltage response to the magnetic component B of an electromagnetic signal, are under consideration. As such cells, bi-SQUIDs and cells based on two parallel SQIF structures that are differentially connected are proposed. Series arrays of cells with linear voltage response, including an antenna prototype, are fabricated using standard niobium technology with a critical current density of Josephson junctions of 4.5 kA/cm² and are studied experimentally. The data obtained allow estimation of the achievable dV/dB conversion factor and the sensitivity ??B for an antenna integrated with a magnetic flux converter, placed on an available area of 3.3 × 3.3 mm of a chip 5 × 5 mm in size. These values are found to be 10 ??V/nT and 20 fT/Hz^1/2, respectively. The conversion factor increases in proportion with the area a ² occupied by the antenna with a square flux converter, and the sensitivity is improved as a ^?3/2.     

Thermoelectric ac Josephson effect in SNS junctions

It was experimentally evidenced, that Josephson radiation from an SNS junction exists, when a heat flow across the junction exceeds a critical value P_c. The ac component of the thermoelectric voltage was observed directly. The heat-flux-voltage characteristic of a TaCuTa junction showed steps of constant voltage, when the junction was irradiated by an external electromagnetic field at frequenct ～ 10² Hz.     

Submillimeter-wave Josephson spectroscopy

A Josephson high-temperature superconducting (HTSC) submillimeter-wave spectrometer is designed, built, and experimentally investigated. The integrated detection structure of the spectrometer includes a YBCO Josephson junction on a bicrystalline boundary, a double-slot or log-periodic antenna, and a low-inductance resistive shunt. The selective detector response and the response at an intermediate frequency of 1.4 GHz are measured under the action of a signal in the frequency range 350–1250 GHz. Three methods of spectroscopy are investigated using this setup: 1) a method of Hilbert spectroscopy with processing of the detector response is implemented; 2) it is found that for a wide Josephson line at intermediate frequency (IF) the response has the same form as the detector response, making it possible to obtain a spectrum and the width of the generation line from IF response measurements; 3) for a narrow Josephson line the IF response corresponds to the regime of conversion with self-pumping. A new method is proposed for calculating the emission spectrum. The method consists of simple shift, summation, and subtraction operations. The advantages of the method are simplicity, high sensitivity, and high resolution. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 5, 338–343 (10 September 1999)     

Double-slot antennas on extended hemispherical and elliptical quartz dielectric lenses

In this paper, the theoretical far-field patterns and Gaussianbeam coupling efficiencies are investigated for a double-slot antenna placed on quartz hemispherical lenses with varying extension lengths. The radiation patterns of the double-slot antenna are computed using ray-tracing inside the lens and electric and magnetic field integration on the spherical dielectric surface. The theoretical results are equally valid for double-dipole, log-periodic, and spiral antennas, and are presented in extension length/radius and radius/. Therefore, the results yield universal design curves for quartz lenses of different diameters and at different frequencies and using different antennas. The results indicate that forsingle units, there exists a wide range of extension lengths (ext. length/radius=0.61 to 0.76) which result in high Gaussian-coupling efficiencies to moderately highf/# systems. Forimaging array applications with high packing densities, an extension length/radius=0.82 to 0.93 (depending on frequency) will result in peak directivity and highest packing density but lower Gaussian-coupling efficiencies.     

Ambient temperature or moderately cooled semiconductor hot electron bolometer for mm and sub-mm regions

A model of semiconductor hot electron bolometer (SHEB), in which electromagnetic radiation heats only electrons in narrow-gap semiconductor without its lattice slow-response heating, is considered. Free carrier heating changes the generation-recombination processes that are the reason of semiconductor resistance rise. It is estimated, that Hg_0.8Cd_0.2Te detector noise equivalent power (NEP) for mm and sub-mm radiation wavelength range can reach NEP ∼10⁻¹¹ W at Δf = 1 Hz signal gain frequency bandwidth. Measurements performed at electromagnetic wave frequencies v = 36, 39, 55, 75 GHz, and at 0.89 and 1.58 THz too, with non-optimized Hg_0.8Cd_0.2Te antenna-coupled bolometer prototype confirmed the basic concept of SHEB. The experimental sensitivity S_v ∼2 V/W at T = 300 K and the calculated both Johnson-Nyquist and generation-recombination noise values gave estimation of SHEB NEP ∼3.5 × 10⁻¹⁰ W at the band-width Δf = 1 Hz and v = 36 GHz.     

Low noise submillimeter SIS receiver with niobium nitride quasiparticle tunnel junctions

We have developed and tested a submillimeter waveguide SIS mixer with NbN-MgO-NbN quasiparticle tunnel junctions. The two junction array is integrated in a full NbN printed circuit. The NbN film critical temperature is 15 K and the junction gap voltage is 5 mV. The size of the junctions is 1.4 × 1.4 µm and Josephson critical current density is about 1.5 KA/cm² resulting in junction R_NC product about 40. The inductive tuning circuit in NbN is integrated with each junction in two junction array. A single non contacting backshort was tuned at each frequency in the mixer block.At 306 GHz the minimum DSB receiver noise temperature is as low as 230 K. The sources of the receiver noise and of the limits of the NbN SIS submillimeter mixer improvement are discussed.     

嵌入到Fabry-Perot谐振腔的双晶约瑟夫森结阵列的阻抗匹配和相位锁定研究

在He等人所做的嵌入到Fabry-Perot谐振腔中约瑟夫森结阵列的微波辐照研究基础上,提出了同时实现约瑟夫森结阵列阻抗匹配和相位锁定的方法,进行了相关的电磁仿真和数值计算.双晶约瑟夫森结阵列被制作在YSZ双晶基片上,同时被嵌入到Fabry-Perot谐振腔内.通过在基片上制作与结阵列集成的串联馈电半波偶极天线阵,并对其结构进行优化实现了结与天线的匹配,数值计算表明结的辐射效率达到94%;利用天线阵辐射场的特征和对模型合理的设计,使Fabry-Perot谐振腔和基片同时谐振在合适的模式下,从而使结阵列与谐 关键词： 约瑟夫森结阵列 阻抗匹配 相位锁定 Fabry-Perot谐振腔     

基于VO2薄膜非致冷红外探测器光电响应研究

VO₂薄膜是非致冷微测辐射热红外探测器热敏电阻材料.研究中应用微电子工艺制备了VO₂溅射薄膜红外探测器,在296K的环境中测试了该探测器在不同的直流偏置、光调制频率下对873K标准黑体源8—12μm红外辐射的光电响应以及器件的噪声电压,在10和30Hz的调制频率下其响应率分别大于17kV/W和接近10kV/W.该探测器实现了探测率D大于1.0×10⁸cm (Hz)^1/2/W,热时间常量为0.011s的8—12μm非致冷 关键词： 非致冷测辐射热探测器 红外探测器 二氧化钒 薄膜     

Sub-THz radiation room temperature sensitivity of long-channel silicon field effect transistors

Room temperature operating n-MOSFETs (n-type metal-oxide silicon field effect transistors) used for registration of sub-THz (sub-terahertz) radiation in the frequency range ν = 53−145 GHz are considered. n-MOSFETs were manufactured by 1-μm Si CMOS technology applied to epitaxial Si-layers (d ≈15 μm) deposited on thick Si substrates (d = 640 μm). It was shown that for transistors with the channel width to length ratio W/L = 20/3 μm without any special antennas used for radiation input, the noise equivalent power (NEP) for radiation frequency ν ≈76 GHz can reach NEP ∼6×10⁻¹⁰ W/Hz^1/2. With estimated frequency dependent antenna effective area S_est for contact wires considered as antennas, the estimated possible noise equivalent power NEP_pos for n-MOSFET structures themselves can be from ∼15 to ∼10³ times better in the specral range of ν ∼55–78 GHz reaching NEP_pos ≈10⁻¹² W/Hz^1/2.     

Quasioptical superconducting hot electron bolometer for submillmeter waves

We report on a superconducting hot electron bolometer coupled to radiation via a broadband antenna. The bolometer, a structured NbN film, was patterned on a thin dielectric membrane between terminals of a gold slotline antenna. We investigated the response to submillimeter radiation (wave-lengths 0.1 mm to 0.7 mm) in the fundamental Gaussian mode. We found that the directivity of the antenna was constant within a factor of 2.5 through the whole experimental range. The noise equivalent power of the bolometer at 119 µm was 3 · 10^–13 W/Hz^1/2; a time constant of 160 ps was estimated.     

Normal-metal hot-electron bolometer with Andreev reflection from superconductor boundaries

This paper describes the design and experimental testing of a high-sensitivity hot-electron bolometer based a film of normal metal, exploiting the Andreev reflection from superconductor boundaries, and cooled with the help of a superconductor-insulator-normal metal junction. At the measured thermal conductivity, G≈6×10⁻¹² W/K, and a time constant of τ=0.2 μs, and a temperature of 300 mK, the estimated noise-equivalent power NEP=5×10⁻¹⁸ W/Hz^1/2, assuming that temperature fluctuations are the major source of noise. At a temperature of 100 mK, the thermal conductivity drops to G≈7×10⁻¹⁴ W/K, which yields NEP=2×10⁻¹⁹ W/Hz^1/2 at a time constant of τ=5 μs. The microbolometer has been designed to serve as a detector of millimeter and FIR waves in space-based radio telescopes. Zh. éksp. Teor. Fiz. 115, 1085–1092 (March 1999)