Low Noise Temperature Research Articles

Sensitivity evaluation of optical receiver mixers

In optical receivers for realisation of procedures of heterodyning of a signal, both at a stage of formation, and at reception, as a rule, diodes are used. At the same time diodes, being electronic devices, are characterised by internal noises, which limit the sensitivity of reception. The nature of internal noise of electronic devices is determined by thermal processes and shot effect, which in their turn are determined not only by the ambient background temperature, but also by the frequency of received radiations. To present the results of estimation of the threshold sensitivity of diode mixers in heterodyning paths of optical receivers. Results are presented on the development of an approach to sensitivity estimation of heterodyne receiver mixer estimation. Estimation expressions for calculating the internal noise level of an optical mixer are obtained. The approach of shot noise estimation characterising the threshold sensitivity from the position of noise temperature is proposed. Simplified expressions of dependence of threshold sensitivity as a function of radiation frequency at a given temperature are obtained. Noise values in terms of temperature for different frequencies are calculated. A practical method of measuring the noise temperature, which characterises the sensitivity of reception, based on measuring the output voltage when receiving signals from sources with known temperatures of emitters, is substantiated. The values of the signal-to-noise ratio of the threshold sensitivity for different frequency ranges are presented. The obtained analytical expressions allow us to conclude that the rational solution is the choice of the frequency range in the region of 0.1…1 THz, because it is characterised by a relatively low noise temperature, but at the same time it is able to provide a high speed of message transmission.

Global shutter CMOS vision sensors and event cameras for on‐chip dynamic information

AbstractThe on‐chip extraction of dynamic information from a scene can be addressed with either frame‐based CMOS vision, also called smart image sensors, or dynamic vision sensors, also known as event cameras. When implemented with a pinned photodiode (PPD) as a 4‐transistor active pixel sensor (4T‐APS), the former brings about the benefits of low temporal noise and dark current but without high dynamic range (HDR). The latter comes with the benefits of HDR and a fast event detection rate with low power consumption. The drawback is the background activity noise, which leads to additional hardware or algorithms to keep it low. This paperanalyses the mismatch and noise of a global shutter 4T‐APS implementation with local HDR through an overflow capacitor and correlated double sampling (CDS) to provide low noise events through frame differencing. The aim is to narrow the gap with dynamic vision sensors in terms of event rate and dynamic range. We show that our solution would be competitive with event cameras in scenarios with slow moving objects and a relatively wide dynamic range (85 dB).

VCO Design With Uniformly Low Phase Noise Versus Frequency and Temperature for $D$-Band Applications

VCO Design With Uniformly Low Phase Noise Versus Frequency and Temperature for $D$-Band Applications

InGaAs/AlInAsSb avalanche photodiodes with low noise and strong temperature stability

High-sensitivity avalanche photodiodes (APDs) are used to amplify weak optical signals in a wide range of applications, including telecommunications, data centers, spectroscopy, imaging, light detection and ranging, medical diagnostics, and quantum applications. This paper reports antimony-based separate absorption, charge, and multiplication structure APDs on InP substrates. Al0.7In0.3As0.79Sb0.21 is used for the multiplier region, and InGaAs is used as the absorber. The excess noise is comparable to that of silicon APDs; the k-value is more than one order of magnitude lower than that of APDs that use InP or InAlAs for the gain region. The external quantum efficiency without an anti-reflection coating at 1550 nm is 57%. The gradient of the temperature coefficient of avalanche breakdown voltage is 6.7 mV/K/μm, which is less than one-sixth that of InP APDs, presenting the potential to reduce the cost and complexity of receiver circuits. Semi-insulating InP substrates make high-speed operation practical for widely reported AlxIn1−xAsySb1−y-based APDs.

Demonstration of High-Performance GaN-Based Hall Sensors on Si Substrate by Simulation and Experiment Verification

This work demonstrates high-performance wide bandgap GaN-based Hall sensors by theoretical simulation and experimental verification on 6-in wafer. Compared with the conventional fourfold rotationally symmetric cross-shaped structure, the twofold symmetric one has more flexible parameter selection and is able to exhibit better overall performances. The effects of different input and output aspect ratios on the device characteristics are investigated in detail. The simulation data show that the geometric factor and sensitivity of the devices are obviously improved with the increase of the aspect ratio of the input and output terminals, which is also demonstrated by the experimental results from the fabricated Hall sensors. The temperature drift coefficient is found to be less than 100 ppm/K in a wide temperature range of 300–675 K, and the minimum offset voltage is only 52 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{V}$ </tex-math></inline-formula> when the input current is kept at 1.0 mA. In addition, the angle- and noise-related characteristics of the devices are also investigated, and the root-mean-square voltage noise is determined to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.48~\mu \text{V}$ </tex-math></inline-formula> . Finally, the good uniformity of the 6-in wafer was verified. The low working noise and good temperature stability in a wide temperature range endow the fabricated GaN-based magnetic sensors with promising applications in harsh and high-temperature environments.

Multimode Physics in the Mode Locking of Semiconductor Quantum Dot Lasers

Quantum dot lasers are an attractive option for light sources in silicon photonic integrated circuits. Thanks to the three-dimensional charge carrier confinement in quantum dots, high material gain, low noise and large temperature stability can be achieved. This paper discusses, both theoretically and experimentally, the advantages of silicon-based quantum dot lasers for passive mode-locking applications. Using a frequency domain approach, i.e., with the laser electric field described in terms of a superposition of passive cavity eigenmodes, a precise quantitative description of the conditions for frequency comb and pulse train formation is supported, along with a concise explanation of the progression to mode locking via Adler’s equation. The path to transform-limited performance is discussed and compared to the experimental beat-note spectrum and mode-locked pulse generation. A theory/experiment comparison is also used to extract the experimental group velocity dispersion, which is a key obstacle to transform-limited performance. Finally, the linewidth enhancement contribution to the group velocity dispersion is investigated. For passively mode-locked quantum dot lasers directly grown on silicon, our experimental and theoretical investigations provide a self-consistent accounting of the multimode interactions giving rise to the locking mechanism, gain saturation, mode competition and carrier-induced refractive index.

An Image Localization System Based on Single Photon

As an essential part of artificial intelligence, many works focus on image processing which is the branch of computer vision. Nevertheless, image localization faces complex challenges in image processing with image data increases. At the same time, quantum computing has the unique advantages of improving computing power and reducing energy consumption. So, combining the advantage of quantum computing is necessary for studying the quantum image localization algorithms. At present, many quantum image localization algorithms have been proposed, and their efficiency is theoretically higher than the corresponding classical algorithms. But, in quantum computing experiments, quantum gates in quantum computing hardware need to work at very low temperatures, which brings great challenges to experiments. This paper proposes a single-photon-based quantum image localization algorithm based on the fundamental theory of single-photon image classification. This scheme realizes the operation of the mixed national institute of standards and technology database (MNIST) quantum image localization by a learned transformation for non-noise condition, noisy condition, and environmental attack condition, respectively. Compared with the regular use of entanglement between multi-qubits and low-temperature noise reduction conditions for image localization, the advantage of this method is that it does not deliberately require low temperature and entanglement resources, and it improves the lower bound of the localization success rate. This method paves a way to study quantum computer vision.

L-band cryogenic radio astronomy receiver front-end of the Square Kilometre Array

This paper describes the design and measured performance of the band 2 (L-band, 950 MHz–1760 MHz) cryogenic receiver front-end of the Square Kilometre Array (SKA) radio telescope dish array. The system comprises a wide flare-angle axially corrugated conical horn, a dual linearly polarized orthogonal mode transduce, a noise injection directional coupler, and two amplification stages. Its compact design and cryogenic cooling allow for a very low receiver noise temperature, and it presents another step in the continuous improvement of the noise temperature performance. A Gifford–McMahon cooler physically cools the OMT with its integrated directional coupler to around 70 K, and the first stage low-noise amplifier to about 15 K. A bespoke measurement setup was designed to measure the system’s performance. The measured receiver noise is about 6 K across the frequency band.

Noise Performance and Thermalization of a Single Electron Transistor using Quantum Fluids

We report on low-temperature noise measurements of a single electron transistor (SET) immersed in superfluid 4He. The device acts as a charge sensitive electrometer able to detect the fluctuations of charged defects in close proximity to the SET. In particular, we measure telegraph switching of the electric current through the device originating from a strongly coupled individual two-level fluctuator. By embedding the device in a superfluid helium immersion cell, we are able to systematically control the thermalizing environment surrounding the SET and investigate the effect of the superfluid on the SET noise performance. We find that the presence of superfluid 4He can strongly suppress the switching rate of the defect by cooling the surrounding phonon bath.

Search for dark photon dark matter: Dark E field radio pilot experiment

We are building an experiment to search for dark matter in the form of dark photons in the nano- to milli-eV mass range. This experiment is the electromagnetic dual of magnetic detector dark radio experiments. It is also a frequency-time dual experiment in two ways: We search for a high-Q signal in wide-band data rather than tuning a high-$Q$ resonator, and we measure electric rather than magnetic fields. In this paper we describe a pilot experiment using room temperature electronics which demonstrates feasibility and sets useful limits to the kinetic coupling $\epsilon \sim 10^{-12}$ over 50--300 MHz. With a factor of 2000 increase in real-time spectral coverage, and lower system noise temperature, it will soon be possible to search a wide range of masses at 100 times this sensitivity. We describe the planned experiment in two phases: Phase-I will implement a wide band, 5-million channel, real-time FFT processor over the 30--300 MHz range with a back-end time-domain optimal filter to search for the predicted $Q\sim 10^6$ line using low-noise amplifiers. We have completed spot frequency calibrations using a biconical dipole antenna in a shielded room that extrapolate to a $5 \sigma$ limit of $\epsilon\sim 10^{-13}$ for the coupling from the dark field, per month of integration. Phase-II will extend the search to 20 GHz using cryogenic preamplifiers and new antennas.

Deep reflector prime focus feed for space communication

In this paper, design of a prime-focus feed for a deep reflector, Earth–Moon–Earth space communication system is described. The feed is based on a circular waveguide equipped with two chokes in order to minimise sidelobes and illuminate the deep dish with a high aperture efficiency of 70 % . Based on sun noise measurements, it is estimated that the antenna system presents very low noise temperature values, below 30 K, making this feed favourable for space communication.

A temperature measurement system with high resolution and low noise

Due to the temperature fluctuation, both the self-gravity disturbance level of the gravitational wave detection vehicle and the laser interference measurement system are affected, which brings great noise to the gravitational wave measurement, and the temperature field fluctuation has become one of the most important noise sources of the inertial sensor. In order to ensure the noise level of the inertial sensor to meet the needs of detection, this paper uses the AC bridge to reduce the self-noise of the temperature measurement system, improve the resolution of the temperature measurement system, and realize a high-resolution and low-noise temperature measurement system. The experimental results show that the effective value of self-noise of the temperature measurement system is about 3.65 × 10[Formula: see text], and the long-period noise is less than 1 × 10[Formula: see text]. It can be used in the space gravitational wave detection test and control system.

High-resolution impedance mapping using electrically activated quantitative phase imaging

Retrieving electrical impedance maps at the nanoscale rapidly via nondestructive inspection with a high signal-to-noise ratio is an unmet need, likely to impact various applications from biomedicine to energy conversion. In this study, we develop a multimodal functional imaging instrument that is characterized by the dual capability of impedance mapping and phase quantitation, high spatial resolution, and low temporal noise. To achieve this, we advance a quantitative phase imaging system, referred to as epi-magnified image spatial spectrum microscopy combined with electrical actuation, to provide complementary maps of the optical path and electrical impedance. We demonstrate our system with high-resolution maps of optical path differences and electrical impedance variations that can distinguish nanosized, semi-transparent, structured coatings involving two materials with relatively similar electrical properties. We map heterogeneous interfaces corresponding to an indium tin oxide layer exposed by holes with diameters as small as ~550 nm in a titanium (dioxide) over-layer deposited on a glass support. We show that electrical modulation during the phase imaging of a macro-electrode is decisive for retrieving electrical impedance distributions with submicron spatial resolution and beyond the limitations of electrode-based technologies (surface or scanning technologies). The findings, which are substantiated by a theoretical model that fits the experimental data very well enable achieving electro-optical maps with high spatial and temporal resolutions. The virtues and limitations of the novel optoelectrochemical method that provides grounds for a wider range of electrically modulated optical methods for measuring the electric field locally are critically discussed.

High-bandwidth, variable-resistance differential noise thermometry.

We have developed Johnson noise thermometry applicable to mesoscopic devices with variable source impedance with high bandwidth for fast data acquisition. By implementing differential noise measurement and two-stage impedance matching, we demonstrate noise measurement in the frequency range of 120 MHz-250MHz with a wide sample resistance range of 30 Ω-100kΩ tuned by gate voltages and temperature. We employed high-frequency, single-ended low noise amplifiers maintained at a constant cryogenic temperature in order to maintain the desired low noise temperature. We have achieved thermometer calibration with temperature precision up to 650 μK measuring a 200 mK temperature modulation on a 10K background with 30s of averaging. Using this differential noise thermometry technique, we measured thermal conductivity on a bilayer graphene sample spanning the metallic and semiconducting regimes in a wide resistance range, and we compared it to the electrical conductivity.

On the Theory and Design of Cold Resistors

The concept of using special electrical circuit design to realize “cold resistors”, i.e., an active resistor circuitry with lower effective noise temperature, was first introduced about 80 years ago. Later on, various kinds of artificial resistors were applied in different research areas, such as gravitational wave detection, photo-amplifiers and quartz oscillators. Their proofs of concepts were experimentally proved. Unfortunately, the complete theory was not found even though several attempts had been published, sometimes with errors. In this paper, we describe a correct and complete circuit theoretical model of a cold resistor system. The results are confirmed by computer simulations. A design tool for this circuit is also shown.

A cantilever torque magnetometry method for the measurement of Hall conductivity of highly resistive samples.

We present the first measurements of Hall conductivity utilizing a torque magnetometry method. A Corbino disk exhibits a magnetic dipole moment proportional to Hall conductivity when voltage is applied across a test material. This magnetic dipole moment can be measured through torque magnetometry. The symmetry of this contactless technique allows for the measurement of Hall conductivity in previously inaccessible materials. Finally, we calculate a low-temperature noise bound, demonstrate the lack of systematic errors, and measure the Hall conductivity of sputtered indium tin oxide.

Performance of Low-Noise Ferrite Shield in a K-Rb-21Ne Co-Magnetometer

Spin-exchange relaxation-free (SERF) co-magnetometer is considered to be a promising nuclear spin gyroscope due to its ultrahigh rotation measurement sensitivity and magnetic field disturbance cancellation ability. Recent experiments indicate that the relaxation of the noble-gas spins would result in reduction of the magnetic field disturbance cancellation ability, which means that magnetic noise from the passive magnetic shield in a SERF co-magnetometer can cause rotation rate measurement error. In this paper, the magnetic field frequency response of a SERF atomic magnetometer is derived based on state space method and the magnetic noise of different shield materials are measured. The magnetic noise error model in a SERF co-magnetometer is then derived and the magnetic noise induced rotation rate measurement error is quantitatively evaluated. The superiority of ferrite shield is shown by the performance of a K-Rb-21Ne co-magnetometer. Experimental results show that ferrite shield with lower magnetic noise and better temperature stability is a more favorable choice for the inner shield of the co-magnetometer.

Low-noise, High-PSRR and Positive-TC Voltage Reference for a Temperature- and Supply-compensated CMOS Ring Oscillator

A new CMOS voltage source is designed to provide a low-noise, high-PSRR, and positive temperature coefficient (TC) voltage reference, which is required to compose a regulator to compensate for the effect of temperature and supply-voltage variations in CMOS ring oscillators. With a TSMC 90 nm CMOS process, the proposed circuit improves the supply- and temperaturesensitivity of a CMOS inverter-based ring oscillator by more than 28 dB ±10% of VDD and by 30 dB from -40oC to 100oC, respectively.

Deep levels analysis in wavelength extended InGaAsBi photodetector

InP based dilute bismide InGaAsBi material is emerging as a promising candidate for extending short wavelength infrared detection. One critical factor to limit the performance of these InGaAsBi photodiodes is dark current caused by defects within the material. In this work, low frequency noise spectroscopy (LFNS) and temperature varied photoluminescence was used to characterize the defect levels in the devices. Three deep levels located at Ec − 0.33 eV, Ev + 0.14 eV, and Ec − 0.51 eV were identified from the LFNS spectra, which are consistent with emission peak energy found by photoluminescence spectra of InGaAsBi.

A High-Order L-Band HTS Filter for Sensitive Detecting

In this paper, a new high-temperature superconducting (HTS)-based microwave radiometer with an improved sensitivity is presented. The cryogenic receiver front end consists of an HTS filter and a cryogenic low noise amplifier (LNA). The cryogenic receiver front end shows an ultra-low noise figure and can suppress radio frequency interference (RFI) effectively. The proposed HTS filter works at a center frequency of 1.4135 GHz with a bandwidth of 25 MHz. The measured mid-band insertion loss, side band steepness, and out-of-band attenuation of the HTS filter are 0.14 dB, 35 dB/MHz, and 80 dB, respectively. The noise figure of the cryogenic LNA is about 0.27 dB at a temperature of 77 K. Compared with other total power radiometers, the proposed radiometer has a lower receiver noise temperature, which can improve the sensitivity with a short integration time of the satellite-based salinity meter. In addition, since the bandwidth of the salinity meter is fixed and the integration time of satellite-based equipment is limited, such a low receiver noise temperature can increase the flexibility of future satellite payload configuration program.