Ultrasensitive Detectors Research Articles

Broadband and Ultrasensitive Graphene-Based Mechanical Wave Detector with Nanosecond Response Used for Biological Photoacoustic Imaging.

Achieving broadband and sensitive mechanical wave detection with fast time response remains a great challenge. Here, we exploited the polarization-sensitive absorption characteristics and ultrafast photoelectric response of graphene to construct a broadband and ultrasensitive detector with a nanosecond response for mechanical wave detection. The unprecedented performance of the graphene-based detector allowed us to detect high-frequency mechanical waves over 100 MHz with a detection limit of 0.18 kPa. Moreover, we applied the detector in high-contrast photoacoustic imaging of human hairs and a mouse hindlimb to demonstrate its capability in detection of photoacoustic waves. This device could also find application in other areas such as THz detection and modulation.

Ultrasensitive graphene position-sensitive detector induced by synergistic effects of charge injection and interfacial gating

Abstract Position-sensitive detectors (PSDs) are essential components to the realization of displacement and vibration detection, optical remote control, robot vision, etc. The light sensitivity of PSDs is a crucial parameter, which determines the operating range or detection accuracy of the measurement systems. Here, we devise an ultrasensitive PSD based on graphene/Si hybrid structure by using the synergistic effect of charge injection and interfacial gating. Photogenerated carriers in Si are separated by the built-in electric field at the surface. Holes diffuse laterally in inversion layer and then inject into graphene to form photoresponse. Meanwhile, the electrons in bulk Si that move to the area under graphene cause a gating effect, thus introducing a high gain. With the benefit of synergistic effect, the detection limit power of our device can be pushed to pW level, which is reduced by two orders of magnitude compared to previously reported graphene based PSD. Furthermore, even for infrared light of 1064 nm, the PSD still retains position sensitivity to 1 nW weak light, as well as fast response speed at the μs level. This work provides the potential of graphene as a promising material for ultraweak light position sensitive detection.

Ultrasensitive and stable X-ray detection using zero-dimensional lead-free perovskites

Abstract Sensitive and reliable X-ray detectors are essential for medical radiography, industrial inspection and security screening. Lowering the radiation dose allows reduced health risks and increased frequency and fidelity of diagnostic technologies for earlier detection of disease and its recurrence. Three-dimensional (3D) organic–inorganic hybrid lead halide perovskites are promising for direct X-ray detection – they show improved sensitivity compared to conventional X-ray detectors. However, their high and unstable dark current, caused by ion migration and high dark carrier concentration in the 3D hybrid perovskites, limits their performance and long-term operation stability. Here we report ultrasensitive, stable X-ray detectors made using zero-dimensional (0D) methylammonium bismuth iodide perovskite (MA3Bi2I9) single crystals. The 0D crystal structure leads to a high activation energy (Ea) for ion migration (0.46 eV) and is also accompanied by a low dark carrier concentration (~ 106 cm−3). The X-ray detectors exhibit sensitivity of 10,620 µC Gyair−1 cm−2, a limit of detection (LoD) of 0.62 nGyair s−1, and stable operation even under high applied biases; no deterioration in detection performance was observed following sensing of an integrated X-ray irradiation dose of ~23,800 mGyair, equivalent to > 200,000 times the dose required for a single commercial X-ray chest radiograph. Regulating the ion migration channels and decreasing the dark carrier concentration in perovskites provide routes for stable and ultrasensitive X-ray detectors.

Superconductor-Ferromagnet Tunnel Junction Thermoelectric Bolometer and Calorimeter with a SQUID Readout

The superconductor-ferromagnet thermoelectric detector (SFTED) is a novel ultrasensitive radiation detector based on the giant thermoelectric effect in superconductor-ferromagnet tunnel junctions. This type of detector can be operated without the need of additional bias lines and is predicted to provide a performance rivaling transition-edge sensors and kinetic inductance detectors. Here, we report our numerical studies on the SFTED noise equivalent power, energy resolution and time constant, and the feasibility of a SQUID readout in both bolometric and calorimetric regimes, with the goal to provide practical design parameters for the detector fabrication and the readout circuitry implementation.

Small scale direct dark matter search experiments

Experiments based on noble liquids and solid state cryogenic detectors have had a leading role in the direct detection of dark matter. But smaller scale projects can help to explore the new dark matter landscape with advanced, ultra-sensitive detectors based on recently developed technologies. Here, the physics case of different types of small scale dark matter experiments will be presented and many of them will be reviewed, highlighting the detection techniques and summarizing their properties, results and status.

Real-time fiber-based fluorescence lifetime imaging with synchronous external illumination: A new path for clinical translation.

Time-correlated single photon counting is the "gold-standard" method for fluorescence lifetime measurements and has demonstrated potential for clinical deployment. However, the translation of the technology into clinic is hindered by the use of ultrasensitive detectors, which make the fluorescence acquisition impractical with bright lighting conditions such as in clinical settings. We address this limitation by interleaving periodic fluorescence detection with synchronous out-of-phase externally modulated light source, thus guaranteeing specimen illumination and a fluorescence signal free from bright background light upon temporal separation. Fluorescence lifetime maps are generated in real-time from single-point measurements by tracking a reference beam and using the phasor approach. We demonstrate the feasibility and practicality of this technique in a number of biological specimens, including real-time mapping of degraded articular cartilage. This method is compatible and can be integrated with existing clinical microscopic, endoscopic and robotic modalities, thus offering a new pathway towards label-free diagnostics and surgical guidance in a number of clinical applications.

EP1.11-07 Development of a Chromosome Instabilities in Plasma Cell-Free DNA Assay for Early Lung Cancer Detection and Treatment Response Monitoring

Chromosomal instability (CIN) is one of the hallmarks of cancer. Tumor cells keep shedding DNA into blood stream which provides an opportunity for CIN analysis. Here we present a retrospective study to investigate the potential of CIN in plasma cell-free DNA (cfDNA) as a minimal-invasive biomarker for early cancer detection and cancer treatment responses monitoring. To characterization the baseline data of CIN in cfDNA, 171 plasma samples were collected since June 2017. 35 was from non-cancer individuals. 136 was from cancer patients. cfDNA was extracted and sent to low-coverage genome sequencing on the Illumina X10 platform, followed by chromosomal instability (CIN) analyses by a customized workflow Ultrasensitive Chromosomal Instability Detector (UCAD). Increased plasma cfDNA CIN was observed along with disease progression. In lung cancer, cfDNA CIN increased along with the development of lesions, from adenocarcinoma in-situ, minimal invasive adenocarcinoma, invasive adenocarcinoma (P=0.034) to relapsed cancer (P<0.01). The sensitivity of early lung cancer detection was 30.7%, 37.5%, 45.5%, 50.0% and 98.1% for AIS, MIA, IAC, SCC and relapsed lung cancer, at a specificity of 75%. In primary lung cancer, cfDNA CIN decreased after curative therapies. And cfDNA CIN significantly increased after disease relapsed (P<0.01). And cfDNA levels did not show statistical differences regarding metastases sites. cfDNA CIN can help early cancer detection and treatment response monitoring.

To Repeat or Not to Repeat: An Evaluation of Critical Values in Chemistry Laboratory Testing

Abstract It is common laboratory practice to repeat critical values before reporting the result. However, the benefits of repeat testing are unclear. There are slight differences in values whenever tests are repeated, owing to the inherent imprecision of instruments. Repeating critical values delays reporting of results and, ultimately, clinical intervention. Modern instruments have ultrasensitive level sensors, clot detectors, and better precision, making this practice costly and clinically inefficient. This study aimed to evaluate critical values pairs (original and repeats) to determine if repeats were necessary. Our instruments are programmed to automatically repeat critical values for several analytes. In total, 3,891 critical value pairs (potassium, n = 1111; sodium, n = 677; glucose, n = 987; calcium, n = 214; phosphorus, n = 86; magnesium, n = 399; and bicarbonate/CO2, n = 417) that were performed from April to July 2018 at our core laboratory were analyzed. Data were extracted using software developed to evaluate clinical laboratory data for quality assurance. Analysis of the distribution of critical values within and outside the analytical measurement range (AMR) for each of the analytes was performed. The repeat pairs were analyzed for significant differences (&gt;CAP allowable error), mean absolute and percentage difference between the two determinations, and the number of results that were no longer critical on repeat testing. A cost-time analysis was also performed. For all critical values, a total of 49 (1.26%) showed significant differences between the initial and the repeated results. There were significant differences in 35 (0.92%) of the 3,800 repeats within and in 14 (15.38%) of the 91 repeats outside the AMR. For the 3,800 critical values within the AMR, the mean absolute difference and percent difference between the two testing determinations were: potassium, 0.02 mmol/L (0.42%); sodium, 0.19 mmol/L (0.13%); glucose, 0.44 mg/dL (0.16%); calcium, 0.01 mg/dL (0.14%); phosphorus, 0.01 mg/dL (0.16%); magnesium, 0.01 mg/dL (0.31%); and bicarbonate (CO2), 0.57 mEq/L (1.73%), respectively. A total of 254 (6.53%) initial critical values turned out to be noncritical when repeated, although most were just above or below the cutoff. During the study period, the analytical time for critical value repeats was around 355 hours and the cost was just over $1,300. Data from our study suggest that repeated testing is very similar to the original result and therefore redundant. A higher percentage of results had a significant difference when outside the AMR and repeating just these results can be considered. This study did not capture results that were just below or above the critical value cutoffs, and several of these would have likely been critical on repeat testing. Our analysis suggests that these chemistry critical values should not be routinely repeated, allowing for potential cost savings and improved patient care by reporting critical values sooner, resulting in faster clinical intervention.

Enhancing sensitivity to ambient refractive index with tunable few-layer graphene/hBN nanoribbons

Refractive index (RI) sensing helps to identify biomolecules and chemicals in the mid-infrared range for drug discovery, bioengineering, and environmental monitoring. In this paper, we numerically demonstrate an electrically tunable RI sensor with ultrahigh sensitivity using a three-layer graphene nanoribbon array separated by hexagonal boron nitride (hBN). Unlike the weak resonance in single-layer graphene nanoribbons, a much stronger plasmon resonance featuring a higher-quality factor can be excited in the graphene/hBN few-layer ribbon array. Simultaneously, the high purity of graphene on hBN results in an outstanding charge mobility above 4×104 cm2·V−1·s−1 at 300 K, which allows a larger modulation depth. The interaction between the locally enhanced field around graphene ribbons and its surrounding analyte leads to ultrahigh sensitivity (4.207 μm/RIU), with the figure of merit reaching approximately 58. Moreover, this ultrasensitive detector could selectively work in different wavebands by controlling gate voltages applied to graphene. These merits of ultrahigh sensitivity and electrical tunability are major advances compared to previous RI sensors, paving a way toward ultrasensitive detection using graphene/hBN few-layer devices.

Optical sensing interface based on nano-opto-electro-mechanical systems

A novel optical sensing interface based on nano-opto-electro-mechanical systems (NOEMS) is proposed, in which the light can be coupled with quantum tunneled electrons via weak mechanical coupling. By taking optical pump power and mechanical coupling strength as varying parameters, respectively, bifurcation diagrams of three involved dynamical states of the NOEMS, i.e., optical, electrical and mechanical mode, are calculated, from which an effective coupling region for tunneled electrons and light is revealed. Self-oscillation, transient dynamics and the threshold of the NOEMS are further characterized, and it is found that the effective coupling region has a special transient time. The work sheds light in developing ultra-sensitive photon detectors using physical mechanisms rather than the conventional PN junction based.

Rapid ultrasensitive detection platform for antimicrobial susceptibility testing.

Rapid detection and phenotyping of pathogenic microbes is critical for administration of effective antibiotic therapies and for impeding the spread of antibiotic resistance. Here, we present a novel platform, rapid ultrasensitive detector (RUSD), that utilizes the high reflectance coefficient at high incidence angles when light travels from low- to high-refractive-index media. RUSD leverages a principle that does not require complex manufacturing, labeling, or processing steps. Utilizing RUSD, we can detect extremely low cell densities (optical density [OD] ≥ 5 × 10−7) that correspond to approximately 20 bacterial cells or a single fungal cell in the detection volume, which is nearly 4 orders of magnitude more sensitive than standard OD methods. RUSD can measure minimum inhibitory concentrations (MICs) of commonly used antibiotics against gram-negative and gram-positive bacteria, including Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, within 2 to 4 h. Here, we demonstrate that antibiotic susceptibility tests for several pathogens can rapidly be performed with RUSD using both small inoculum sizes (500 cells/mL) and larger inoculum sizes (5 × 105 cells/mL) used in standard antibiotic susceptibility tests. We anticipate that the RUSD system will be particularly useful for the cases in which antibiotic susceptibility tests have to be done with a limited number of bacterial cells that are available. Its compatibility with standard antibiotic susceptibility tests, simplicity, and low cost can make RUSD a viable and rapidly deployed diagnostic tool.

Development of a plasma cell-free DNA chromosome instabilities assay for early cancer detection and treatment response monitoring of multiple tumor types.

e13072 Background: Tumor cells keep shedding DNA into blood stream. Here we present a retrospective study to investigate the potential of CIN in plasma cell-free DNA (cfDNA) as a minimal-invasive biomarker for early cancer detection and cancer treatment responses monitoring. Methods: To characterization cfDNA CIN, 160 plasma samples from non-cancer individuals and 569 from cancer patients, including tumors from the brain, respiratory tract, gastrointestinal tract, urinary tract, liver, gallbladder, female reproductive system, prostate, breast and sarcoma. cfDNA was extracted and sent to low-coverage whole genome sequencing by the Illumina X10, followed by CIN analyses by a customized workflow Ultrasensitive Chromosomal Instability Detector (UCAD). Results: In non-cancer individuals, increased CIN in cfDNA was found associated with active EBV infections(P&lt;0.01) and HBV infection (P=0.042). No statistical significances were found for the other parameters, including age, hypertension, diabetes, chronic kidney diseases, family history of cancer and etc. cfDNA CIN increased along with the development of lung cancer lesions, from adenocarcinoma in-situ, minimal invasive adenocarcinoma, invasive adenocarcinoma (P=0.034) to relapsed cancer (P&lt;0.01). The sensitivity of early lung cancer detection was 30.7%, 37.5%, 45.5%, 50.0% and 98.1% for AIS, MIA, IAC, SCC and relapsed lung cancer, at a specificity of 75%. cfDNA CIN levels did not show statistical differences regarding metastases sites. cfDNA CIN were further increased in relapsed breast cancer (P&lt;0.01). The sensitivity of relapsed breast cancer detection was 73.3%, 94.4%, 89.6% and 80.0% for HER2+, Luminal A, Luminal B and triple negative breast cancer, at a specificity of 90%. In primary liver cancer, cfDNA CIN decreased after curative therapies, including R0 resections and liver transplant. R0 resections showed similar performance as compared to liver transplant (P=0.35) in terms of cfDNA CIN decreasing. Furthermore, cfDNA CIN was higher in patients after R0 resections (P=0.003) and liver transplant (P=0.03) than that of HBV-positive cancer-free patients, indicating the potential risk of disease relapses. For advanced stage patients, continuously increasing cfDNA CIN level was found associated with worse survival, and a decreasing trend predicting better prognosis vice versa. Conclusions: Plasma cfDNA CIN analysis might be a useful tool for cancer management.

Plasma cell-free DNA chromosomal instability score as early predictor to monitor tumor burden in response to therapeutic in multiple myeloma patients.

8036 Background: Multiple myeloma (MM) is a plasma cell malignancy characterized by chromosomal instabilities (CIN). Here we investigate the potential of cell-free DNA CIN as non-invasive biomarker to predict early response for MM treatments. Methods: In this prospective study, we recruited 11 relapsed/refractory (RRMM) and 19 newly diagnosed (NDMM) patients at Changzheng Hospital. Plasma samples were collected after finished two cycles or one month (RRMM) of therapy, with matched ones before the current regimen. cfDNA was extracted, followed by CIN analyses by using a customized bioinformatics workflow, ultrasensitive chromosomal aneuploidy detector (UCAD). Criteria for response and progression were according to the IMWG (Durie BG et al. 2006). Results: 7 (23%) patients (5 RRMM and 2 NDMM) showed high cfDNA CIN regard as strong positive after two cycles of treatment. Plasma cfDNA CIN profiling found complex clonal evolution compared two cycles to baseline. Multiple genomic regions, including chr7, 17p (TP53), 12q and 3p, were involved in clonal evolution. The degree of cfDNA CIN correlated with myeloma stage and overall survival. Remarkably, of the 5 heavily treated RRMM patients and 1 primary refractory newly diagnosed patient, 3 died within 60 days after the last time of cfDNA detection. Nine patients (30%) of patients showed positive cfDNA CIN after two cycles of treatment, which response rate was 11% (n=1) with SD, 33% (n=3) with MR, and 56% with PR, respectively. Fourteen patients with 5 RRMM and 9 NDMM were detected marginal or negative cfDNA CIN after two cycle’s treatment. The overall response rate in 14 patients was 100%, including 14.3% with a complete response, 14.3% with a very good partial response (VGPR), 57.1% with a PR, and 14.3% with a MR. Of these patients, 3 RRMM who received with more than six lines of therapy, showed positive cfDNA CIN. Subsequently, these three heavily treated RRMM patients have chance to enroll the chimeric antigen receptor T-Cell immunotherapy (CAR-T) therapy (enrolled NCT03093168). Surprisedly, all of them benefit from the CAR-T therapy to improve responses dramatically, meanwhile, the dynamics of total cfDNA concentration correlated with tumor burden to negative. Conclusions: We provide evidence that cfDNA level correlates with tumor burden and response rate in MM. For heavily pre-treated advanced RRMM patients with cfDNA CIN positive were benefit from the CAR-T therapy. Therefore, serial plasma cfDNA analysis is a robust and sensitive tool for monitoring response to therapy.

Hybrid ZnO/ZnO-NPs nanofibres fabricated via electrospinning

Purpose: Due to the growing interest and multitude of possible applications, zinc oxide nanowires, including those doped with ZnO nanoparticles, can became, alongside carbon nanotubes, a very desirable material which use is predicted in the construction of nanogenerators, dye sensitized solar cells, optoelectronics or ultrasensitive gas detectors. Design/methodology/approach: The electrospinning process allows for low-cost and scalable production of fibrous mats with diameters from a few to several hundred nanometers. What is more, electrospinning method has gained popularity also due to its versatility, now it is possible to produce fibres from almost every known polymer and the simplicity and lack of any additional functionalization of the obtained nanomaterials. The application of the calcination process to remove the polymer matrix from the obtained nanofibres results in the creation of ceramic nanofibres. Findings: Among the existing methods for the production of ceramic nanostructures, including the hydrothermal, physical and chemical vapour deposition methods, nanolithography or molecular self-assembly, the electrospinning process creates the possibility of fabricating one-dimensional nanostructures with unprecedented properties, good quality, no additional functionalization and purification. Research limitations/implications: Due to ongoing research on the potential applications of zinc oxide nanostructures, including photovoltaics, sensorics and electronics, the most predictable behaviour and properties of ZnO nanowires characterize those nanomaterials that exhibit a periodic structure of the crystal lattice. Considering the optimization of the parameters of the method of producing ceramic zinc oxide nanowires doped with crystalline ZnO nanoparticles, it is worth analysing the thermal treatment parameters of nanofibres. Practical implications: Although amorphous structure, hybrid ZnO nanofibres could be used as humidity sensors with much higher sensing properties than crystalline ZnO nanostructures. Originality/value: Low-cost, scalable production of ceramic nanofibres for most technical applications.

Graphene Aerogel Based Bolometer for Ultrasensitive Sensing from Ultraviolet to Far-Infrared.

This work uncovers that free-standing partly reduced graphene aerogel (PRGA) films in vacuum exhibit extraordinarily bolometric responses. This high performance is mainly attributed to four structure characteristics: extremely low thermal conductivity (6.0-0.6 mW·m-1·K-1 from 295 to 10 K), high porosity, ultralow density (4 mg·cm-3), and abundant functional groups (resulting in tunable band gap). Under infrared radiation (peaked at 5.8-9.7 μm), the PRGA film can detect a temperature change of 0.2, 1.0, and 3.0 K of a target at 3, 25, and 54 cm distance. Even through a quartz window (transmissivity of ∼0.98 in the range of 2-4 μm), it can still successfully detect a temperature change of 0.6 and 5.8 K of a target at 3 and 28 cm distance. At room temperature, a laser power as low as 7.5 μW from a 405 nm laser and 5.9 μW from a 1550 nm laser can be detected. The detecting sensitivity to the 1550 nm laser is further increased by 3-fold when the sensor temperature was reduced from 295 K to 12 K. PRGA films are demonstrated to be a promising ultrasensitive bolometric detector, especially at low temperatures.

Ultra-sensitive graphene-bismuth telluride nano-wire hybrids for infrared detection.

The myriad technological applications of infrared radiation sensors make the search for ultra-sensitive detectors extremely crucial. Materials such as bismuth telluride (Bi2Te3), having a small bulk band gap of 0.17 eV, are ideal infrared detectors. However, due to the high recombination rate of photo-generated charge carriers in the bulk, the electrical response under optical illumination is typically very weak in these materials. We have circumnavigated this by sensitizing graphene with Bi2Te3 nano-wires. These hybrid devices show an ultra-high sensitivity of ∼106 A W-1, under incident electromagnetic radiation from 940 nm to 1720 nm. The theoretical limit of the noise equivalent power and specific detectivity in these devices are ∼10-18 W Hz-1/2 and ∼1011 Jones respectively, which are comparable to those of some of the best known detectors.

Antenna coupled graphene-FET as ultra-sensitive room temperature broadband THz detector

A high sensitivity, low power (∼1μW to 10 μW), room temperature, antenna coupled, THz (0.8 THz) detector is presented by means field effect transistor (FETs) fabricated on epitaxial-grown graphene on silicon carbide. The contact resistance across the source and drain are made high to study the effect of THz response. It is demonstrated that the energy coupled to the antenna is the important parameter in designing the ultra-sensitive THz detectors rather than the contact resistances and channel conductivity. The realised graphene based detectors shows quite good responsivity (&amp;gt;535 V/W) and noise equivalent power (NEP) (&amp;lt;100pW/Hz0.5). The individual contributions of photo voltage due to plasma wave generation (PWG) and photo thermo-electric effect (PTE) in the effective THz detection is estimated. It is also seen that the temperature of the hot carriers generated in the FET channel due to PTE is varying with the gate bias and not constant as assumed in earlier works. A new method is proposed in this work for calculating the antenna coupling factor which varies with incident THz-radiation power. A comprehensive analytical model is worked out to understand the graphene based detector performance.

Cell-Free DNA Analysis Demonstrates Comprehensive Genomic Profiling and a Facile Method to Sensitively in Multiple Myeloma

Background: Multiple myeloma (MM) is a plasma cell malignancy characterized by complex cytogenetic and molecular abnormalities including translocations involving the immunoglobin heavy chain locus and mutations involving numerous oncogenic signaling pathways. Fluorescence in situ hybridization (FISH) has emerged as the most useful current cytogenetic assessment and provide a new level of insight into the correlation of myeloma prognosis risk model. However, the identification or sorting of malignant cells is required before FISH probes and only involved expansion of the types of probe and number of detectable targets is reached. Cell-free DNA (cfDNA) offers the potential for minimally invasive genome-wide profiling of tumor alterations without tumor biopsy and may be associated with cancer precision medicine and patient prognosis.Methods: In this retrospective cohort study, we identified 37 patients from 9 relapsed/refractory (RR) and 33 newly diagnosed (ND) patients were analyzed for chromosomal copy number imbalance using the ultrasensitive chromosomal aneuploidy detector (UCAD) platform.Results: Chromosome copy number aberration (CNA) were frequently (82.6%, N=46) detected in MM plasma cell free DNA. Applying UCAD to cfDNA, FISH in CD138 purified bone marrow aspirates, and some matched bone marrow biopsies, we find concordance in copy number alterations (~81%) between liquid and tumor biopsies. Significant copy number changes, including 1q gains, 13q deletion and 17p deletion could be found in 57.89%, 54.05%, and 16.67% in plasma of MM, which is higher percentage than FISH assay (46.81%, 28.26%, and 8.89%), respectively. Besides, chromosome 6p and 6q were determined the higher frequency aberration from UCAD. Moreover, a higher frequency of copy number aberrations and variations was detected in RR patients than ND (100% vs 78.4%, respectively), obviously CNAs heterogeneity displayed in advanced disease. In the inconsistent some samples, UCAD from the plasma and bone marrow showed the similar results, which indicated the FISH is underdetermined and insensitivity in some patients' routine inspection.Conclusion: We conclude that cfDNA analysis as an adjunct to BM biopsy represents a noninvasive and broaden the applicability strategy for comprehensive genomic profiling and therapeutic monitoring of MM. DisclosuresNo relevant conflicts of interest to declare.

Thermoelectric Radiation Detector Based on Superconductor-Ferromagnet Systems

We suggest a new type of an ultrasensitive detector of electromagnetic fields exploiting the giant thermoelectric effect recently found in superconductor/ferromagnet hybrid structures. Compared to other types of superconducting detectors where the detected signal is based on variations of the detector impedance, the thermoelectric detector has the advantage of requiring no external driving fields. This becomes especially relevant in multi-pixel detectors where the number of bias lines and the heating induced by them becomes an issue. We propose different material combinations to implement the detector and provide a detailed analysis of its sensitivity and speed. In particular, we perform to our knowledge the first proper noise analysis that includes the cross correlation between heat and charge current noise and thereby describes also thermoelectric detectors with a large thermoelectric figure of merit.

A flux-driven Josephson parametric amplifier for sub-GHz frequencies fabricated with side-wall passivated spacer junction technology

We present experimental results for a Josephson parametric amplifier tailored for readout of ultra-sensitive thermal microwave detectors. In particular, we discuss the impact of fabrication details on the performance. We show that the small volume of deposited dielectric materials enabled by the side-wall passivated spacer niobium junction technology leads to robust operation across a wide range of operating temperatures up to 1.5 K. The flux-pumped amplifier has gain in excess of 20 dB in three-wave mixing and its center frequency is tunable between 540–640 MHz. At 600 MHz, the amplifier adds 105 mK ±9 mK of noise, as determined with the hot/cold source method. Phase-sensitive amplification is demonstrated with the device.