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Two-dimensional (2D) non-layered materials in many aspects differ from their layered counterparts, and the exploration of their physical properties has produced many intriguing findings. However, due to challenges in applying existing experimental techniques to such nanoscale samples, their thermal properties have remained largely uncharacterized, hindering further exploration and device application using this promising material system. Here, we demonstrate an experimental study of thermal conduction in β -In2S3, a typical non-layered 2D material, using a resonant nanoelectromechanical systems (NEMS) platform. We devise a new two-degrees-of-freedom technique, more responsive and sensitive than Raman spectroscopy, to simultaneously determine both the thermal conductivity to be 3.7 W m−1 K−1 and its interfacial thermal conductance with SiO2 as 6.4 MW m−2 K−1. Leveraging such unique thermal properties, we further demonstrate a record-high power-to-frequency responsivity of −447 ppm/μW in β -In2S3 NEMS sensors, the best among drumhead NEMS-based bolometers. Our findings offer an effective approach for studying thermal properties and exploring potential thermal applications of 2D non-layered materials. [ABSTRACT FROM AUTHOR]

Graphene possesses weak electron-phonon interactions, small electron heat capacity, and broad-band absorption, which make it an excellent candidate as a fast and sensitive bolometer. This work studies the bolometric performance of fluorinated graphene (FG) films, which were synthesized using a vacuum filtration-assisted method with FG and chitosan. Thermal annealing (200-1000°C) under an Ar atmosphere was used to modulate the fluorine density. The electrical resistivity and thermal conductivity were measured from 320 to 10 K. As the ratio of F/C reduced from 4.06 to 0.003, the electrical resistivity decreased from 0.37 to 9.6 × 10-5 Ω·m at RT, and the thermal conductivity increased from 0.5 to 2.7 W·m-1·K-1 at RT. In addition, the higher fluorine density resulted in a higher temperature coefficient of resistance (TCR). A mildly reduced FG film with a F/C ratio of 4.06 exhibited the highest |TCR| of 1%·K-1 at 10 K and 0.48%·K-1 at 320 K. The temperature-dependent resistivity revealed that the electrical transport mechanisms are mainly due to a combination conduction processes of thermal activation and variable range hopping. The thermal activation energy reduced from 21 to 1 meV as the concentration of fluorine decreased, which confirms that the conductivity of FG is controlled by fluorinated structures and can be adjusted by thermal annealing treatment. Last, the bolometric performance of FG films was demonstrated across a wide range of wavelengths from ultraviolet to near-IR. The FG films can detect a human hand 25 cm away with good sensitivity and repeatability. For a sample with a suspended length of 1.2 mm, the response time was measured to be 436-449 ms. These results demonstrated that the FG films show great potential as flexible and sensitive bolometric IR sensors. [ABSTRACT FROM AUTHOR]

The 2020 decadal review recognized the measurement of the polarization of the cosmic microwave background (CMB) to be a top priority for the decade. CMB experiments including POLARBEAR2/Simons Array, Atacama Cosmology Telescope/Advanced-ACT, SPT-3G, the Simons Observatory, and CMB-S4 have or will use transition edge sensor (TES) bolometer fabricated with Aluminum doped with Manganese (AlMn). AlMn is a popular material choice as the superconducting transition temperature ( T c ) and normal resistance ( R n ) of the TES can be tuned with Mn concentration, geometric patterning, film thickness, and thermal annealing. In addition the conductivity is appropriate for both time division multiplexing and frequency division multiplexing that require 10 m Ω and 1 Ω sensors respectively. In this paper we present work on the ability to tune the T c of a film based on its time and temperature thermal tuning profile combined with room temperature monitoring of film resistivity. Such control allows for the fabrication of a wide range of TES parameters from a single AlMn concentration. Scanning electron microscope (SEM) imaging shows that the AlMn film's grain boundaries are changed by thermal annealing making the film more conductive and raising its superconducting transition temperatures, and that at high enough temperatures will eventually recover the T c of bulk Al. We find that baking films at ∼ 200 ∘ C for tens of minutes yields a T c that is suitable for 100 mK base temperature experiments and we present on the thermal tune profiles of several different thicknesses of AlMn. [ABSTRACT FROM AUTHOR]

The Simons Observatory (SO) is a cosmic microwave background instrumentation suite in the Atacama Desert of Chile. More than 65,000 polarization-sensitive transition-edge sensor (TES) bolometers will be fielded in the frequency range spanning 27 to 280 GHz, with three separate dichroic designs. The mid-frequency 90/150 GHz and ultra-high-frequency 220/280 GHz detector arrays, fabricated at NIST, account for 39 of 49 total detector modules and implement the feedhorn-fed orthomode transducer-coupled TES bolometer architecture. A robust production-level fabrication framework for these detector arrays and the monolithic DC/RF routing wafers has been developed, which includes single device prototyping, process monitoring techniques, in-process metrology, and cryogenic measurements of critical film properties. Application of this framework has resulted in timely delivery of nearly 100 total superconducting focal plane components to SO with 88 % of detector wafers meeting nominal criteria for integration into a detector module: a channel yield > 95 % and T c in the targeted range. [ABSTRACT FROM AUTHOR]

The digital frequency-domain multiplexing technique is widely used for astrophysical instruments with large detector arrays. Detailed detector characterization is required for instrument calibration and systematics control. We conduct the TES complex electrothermal-feedback response measurement with the DfMux readout system as follows. By injecting a single sideband signal, we induce modulation in TES power dissipation over a frequency range encompassing the detector response. The modulated current signal induced by TES heating effect is measured, allowing for the ETF response characterization of the detector. With the injection of an upper sideband, the TES readout current shows both an upper and a lower sideband. We model the upper and lower sideband complex ETF response and verify the model by fitting to experimental data. The model not only can fit for certain physical parameters of the detector, such as loop gain, temperature sensitivity, current sensitivity, and time constant, but also enables us to estimate the systematic effect introduced by the multiplexed readout. The method is therefore useful for in situ detector calibration and for estimating systematic effects during astronomical telescope observations, such as those performed by the upcoming LiteBIRD satellite. [ABSTRACT FROM AUTHOR]

The Simons Observatory is a cosmic microwave background experiment stationed atop Cerro Toco, at an elevation of 5200 ms in Chile's Atacama Desert. The receivers of the Observatory will contain more than 60,000 transition edge sensor bolometers. In order to read out this large detector count in a scalable manner, we utilize a microwave superconducting quantum interference device (SQUID) multiplexing scheme where each detector is inductively coupled to an rf SQUID, which in turn is inductively coupled to a GHz resonator. More than 2000 SQUIDs and resonators are fabricated on a single 76.2-mm-diameter silicon wafer. To qualify wafers before integration, we cryogenically screen ∼ 10% of the devices on each wafer by use of a standard set of measurements. From these data, we report parameter value trends in 47 wafers that were fabricated in the past two years. We show good control in key parameters such as frequency placement, internal quality factor, and response to applied flux. We demonstrate a wafer acceptance yield of 86%. [ABSTRACT FROM AUTHOR]

The transition-edge sensor (TES) as a type of low-temperature superconducting detector offers superior sensitivity due to its low thermal noise. In this work, we present a prototype TES bolometer designed for cosmic microwave background (CMB) polarization measurements. This TES is made of aluminum doped with a low concentration of manganese (2000 ppm by atomic percentage), and is deposited on the SiNx membrane which connects to the silicon substrate via narrow legs. In order to calculate its electrothermal parameters we have performed dark characterizations, which include measuring voltage-current (IV) curve at different bath temperatures, square-wave time response at various bias voltages, and noise level. This TES bolometer shows a noise equivalent power (NEP) of about 5 × 10 - 17 W/ Hz , which meets the requirement of CMB observation. However, its saturation power is smaller and time constant is larger than what are expected. We have analyzed the reasons and will make corresponding improvements in our future work. [ABSTRACT FROM AUTHOR]

Abstract A straightforward analytical approach is proposed for the design of minimally thin metal absorbers. Unlike traditional resonant design principles, where shape, size, and periodicity of a nanostructured film determine the absorption properties, this study uses only the thickness and permittivity (i.e., sheet conductivity) of the material at hand to demonstrate maximal absorption in the minimal possible thickness at any given wavelength in planar layers – guided by only the derived material‐agnostic equations. An alternative mechanism is further proposed and experimentally demonstrated to obtain precise control over the sheet conductivity of metal films necessary for such designs using metal dilution, enabling the tuning of both the amplitude and the phase of reflected waves. Finally, the concept of “phase doping” is proposed and experimentally demonstrated, wherein an ultrathin metal layer is placed within the spacer of the absorber cavity, which spectrally tunes the absorption feature without changing the spacer thickness or participating in the absorption. By judiciously combining the dilution of the absorbing and phase layers, a multifunctional ultrathin absorber architecture is demonstrated with customizable amplitude, spectral position, and selectivity, all leveraging the same vertical stack. These findings are promising for the design of ultrasensitive detectors, thermal emitters, and nonlinear optical components.

The Simons Observatory (SO) is a cosmic microwave background instrumentation suite being deployed in the Atacama Desert in northern Chile. The telescopes within SO use three types of dichroic transition-edge sensor (TES) detector arrays, with the 90 and 150 GHz Mid-Frequency (MF) arrays containing 65% of the approximately 68,000 detectors in the first phase of SO. All of the 26 required MF detector arrays have now been fabricated, packaged into detector modules, and tested in laboratory cryostats. Across all modules, we find an average operable detector yield of 84% and median saturation powers of (2.8, 8.0) pW with interquartile ranges of (1, 2) pW at (90, 150) GHz, respectively, falling within their targeted ranges. We measure TES normal resistances and superconducting transition temperatures on each detector wafer to be uniform within 3%, with overall central values of 7.5 m Ω and 165 mK, respectively. Results on time constants, optical efficiency, and noise performance are also presented and are consistent with achieving instrument sensitivity forecasts. [ABSTRACT FROM AUTHOR]

It is known that the dielectric layer (resonator) located behind the conducting plate of the bolometer system can significantly increase its sensitivity near the resonance frequencies. In this paper, the possibility of receiving broadband electromagnetic signals in a multilayer bolometric meta-material made of alternating conducting (e.g., silicon semiconductor) and dielectric layers is demonstrated both experimentally and numerically. It is shown that such a multilayer structure acts as a lattice of resonators and can significantly increase the width of the frequency band of efficient electromagnetic energy absorption. The parameters of the dielectric and semiconductor layers determine the frequency bands. Numerical modeling of the effect has been carried out under the conditions of our experiment. The numerical results show acceptable qualitative agreement with the experimental data. This study develops the previously proposed technique of resonant absorption of electromagnetic signals in bolometric structures. [ABSTRACT FROM AUTHOR]

Many applications require monitoring of increasingly high neutron flux levels. Pre‐neutron characterization is performed of a superconducting transition edge bolometric device, sensitive to neutrons by an enriched boron carbide (10B4C) layer. Heat from the absorption of neutrons is simulated using an attenuated laser, while the detector is cooled to the critical temperature, Tc. Frequency dependent (4–25 Hz) and constant input power measurements are performed on a 10B4C‐coated and a non‐coated pixel. Results are used to fit a two lumped element thermal model. The effective specific heat is highly dependent on the input pulse duration due to the interconnected stack structure. For modulated pulses, the active volume in the thermal circuit is the full depth of the substrate in the area under the pixel. For constant power input, a large portion of the substrate is heated and the interface conductivities to the cold finger are found to be important. The detectivity is D* = 3.5 × 108 cmHzW−1${{\rm cm}} \sqrt {{\rm Hz}}\,{{\rm W}^{-1}}$, and is only slightly lower than similar detectors. Understanding the dynamics of the detector better and using neutron excitation, it is expected that optimizations can lead to an equally good detector for cold to thermal neutrons at flux levels >106 n cm−2s−1. [ABSTRACT FROM AUTHOR]

Abstract Many applications require monitoring of increasingly high neutron flux levels. Pre‐neutron characterization is performed of a superconducting transition edge bolometric device, sensitive to neutrons by an enriched boron carbide (10B4C) layer. Heat from the absorption of neutrons is simulated using an attenuated laser, while the detector is cooled to the critical temperature, Tc. Frequency dependent (4–25 Hz) and constant input power measurements are performed on a 10B4C‐coated and a non‐coated pixel. Results are used to fit a two lumped element thermal model. The effective specific heat is highly dependent on the input pulse duration due to the interconnected stack structure. For modulated pulses, the active volume in the thermal circuit is the full depth of the substrate in the area under the pixel. For constant power input, a large portion of the substrate is heated and the interface conductivities to the cold finger are found to be important. The detectivity is D* = 3.5 × 108 cmHzW−1, and is only slightly lower than similar detectors. Understanding the dynamics of the detector better and using neutron excitation, it is expected that optimizations can lead to an equally good detector for cold to thermal neutrons at flux levels >106 n cm−2s−1.

Ambient temperature long‐wavelength infrared (LWIR) photodetection has many critical applications ranging from thermal imaging and optical communications to night vision cameras. Currently, high performance, low cost, air stability, and ultra‐broadband response still constitute challenges. Here, the study demonstrates a high‐performance uncooled LWIR photodetector using 2D hexagonal α‐Fe2O3 single crystal nanoflakes, which are synthesized via chemical vapor deposition. The 2D α‐Fe2O3 photodetector realizes high specific detectivity (D*) of 3.28×109 cmHz1/2 W−1 and very low noise equivalent power of 8.94×10−14 W Hz−1/2 with 10.6 µm laser. The photo bolometer effect is responsible for the photoresponse in the infrared range with a large temperature coefficient resistance of −241.2% K−1. This study shows a new type of potential broadband response material and provides a promising LWIR optoelectrical device with good air stability. [ABSTRACT FROM AUTHOR]

Optoelectronic sampling is the ultimate method to perform ultra‐high frequency analog‐to‐digital conversion. Thanks to the ps photo‐thermo‐bolometric effect in high mobility hexagonal boron nitride (h‐BN) encapsulated graphene, a state‐of‐the‐art optoelectronic sampler over a 40 GHz bandwidth using a 4 ps pulsed laser is demonstrated. The superior transport and optoelectronic linearities of this graphene sampler lead to very high harmonic rejections below –43 dB above 20 GHz. With a physics‐based microscopic model, it is shown that harmonics are generated by optoelectronics saturation effects and only appear when carrier energy reaches that of optical phonons, which is very high in h‐BN encapsulated graphene. This device is the first ultra‐fast optoelectronic sampler based on the bolometric effect. [ABSTRACT FROM AUTHOR]

Ambient temperature long‐wavelength infrared (LWIR) photodetection has many critical applications ranging from thermal imaging and optical communications to night vision cameras. Currently, high performance, low cost, air stability, and ultra‐broadband response still constitute challenges. Here, the study demonstrates a high‐performance uncooled LWIR photodetector using 2D hexagonal α‐Fe2O3 single crystal nanoflakes, which are synthesized via chemical vapor deposition. The 2D α‐Fe2O3 photodetector realizes high specific detectivity (D*) of 3.28×109 cmHz1/2 W−1 and very low noise equivalent power of 8.94×10−14 W Hz−1/2 with 10.6 µm laser. The photo bolometer effect is responsible for the photoresponse in the infrared range with a large temperature coefficient resistance of −241.2% K−1. This study shows a new type of potential broadband response material and provides a promising LWIR optoelectrical device with good air stability. [ABSTRACT FROM AUTHOR]

Abstract Optoelectronic sampling is the ultimate method to perform ultra‐high frequency analog‐to‐digital conversion. Thanks to the ps photo‐thermo‐bolometric effect in high mobility hexagonal boron nitride (h‐BN) encapsulated graphene, a state‐of‐the‐art optoelectronic sampler over a 40 GHz bandwidth using a 4 ps pulsed laser is demonstrated. The superior transport and optoelectronic linearities of this graphene sampler lead to very high harmonic rejections below –43 dB above 20 GHz. With a physics‐based microscopic model, it is shown that harmonics are generated by optoelectronics saturation effects and only appear when carrier energy reaches that of optical phonons, which is very high in h‐BN encapsulated graphene. This device is the first ultra‐fast optoelectronic sampler based on the bolometric effect.

The integration of low-dimensional materials with optical waveguides presents promising opportunities for enhancing light manipulation in passive photonic circuits. In this study, we investigate the potential of aerosol-synthesized single-walled carbon nanotube (SWCNT) films for silicon nitride photonic circuits as a basis for developing integrated optics devices. Specifically, by measuring the optical response of SWCNT-covered waveguides, we retrieve the main SWCNT film parameters, such as absorption, nonlinear refractive, and thermo-optic coefficients, and we demonstrate the enhancement of all-optical wavelength conversion and the photoresponse with a 1.2 GHz bandwidth. [ABSTRACT FROM AUTHOR]

The doubly clamped microelectromechanical system (MEMS) beam resonators exhibit extremely high sensitivity to tiny changes in the resonance frequency owing to their high quality (Q-) factors, even at room temperature. Such a sensitive frequency-shift scheme is very attractive for fast and highly sensitive terahertz (THz) detection. The MEMS resonator absorbs THz radiation and induces a temperature rise, leading to a shift in its resonance frequency. This frequency shift is proportional to the amount of THz radiation absorbed by the resonator and can be detected and quantified, thereby allowing the THz radiation to be measured. In this review, we present an overview of the THz bolometer based on the doubly clamped MEMS beam resonators in the aspects of working principle, readout, detection speed, sensitivity, and attempts at improving the performance. This allows one to have a comprehensive view of such a novel THz detector. [ABSTRACT FROM AUTHOR]

We report on the development of scintillating bolometers based on lithium molybdate crystals that contain molybdenum that has depleted into the double- β active isotope 100 Mo (Li 2 100 depl MoO 4 ). We used two Li 2 100 depl MoO 4 cubic samples, each of which consisted of 45-millimeter sides and had a mass of 0.28 kg; these samples were produced following the purification and crystallization protocols developed for double- β search experiments with 100 Mo-enriched Li 2 MoO 4 crystals. Bolometric Ge detectors were utilized to register the scintillation photons that were emitted by the Li 2 100 depl MoO 4 crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc Underground Laboratory (Spain). We observed that the Li 2 100 depl MoO 4 scintillating bolometers were characterized by an excellent spectrometric performance (∼3–6 keV of FWHM at 0.24–2.6 MeV γ s), moderate scintillation signal (∼0.3–0.6 keV/MeV scintillation-to-heat energy ratio, depending on the light collection conditions), and high radiopurity ( 228 Th and 226 Ra activities are below a few µBq/kg), which is comparable with the best reported results of low-temperature detectors that are based on Li 2 MoO 4 using natural or 100 Mo-enriched molybdenum content. The prospects of Li 2 100 depl MoO 4 bolometers for use in rare-event search experiments are briefly discussed. [ABSTRACT FROM AUTHOR]

The Ricochet reactor neutrino observatory is planned to be installed at Institut Laue–Langevin starting in mid-2022. The scientific goal of the Ricochet collaboration is to perform a low-energy and percentage precision CENNS measurement in order to explore exotic physics scenarios beyond the standard model. To that end, Ricochet will host two cryogenic detector arrays: the CryoCube (Ge target) and the Q-ARRAY (Zn target), both with unprecedented sensitivity to O (10) eV nuclear recoils. The CryoCube will be composed of 27 Ge crystals of 38 g instrumented with NTD-Ge thermal sensor as well as aluminum electrodes operated at 10 mK in order to measure both the ionization and the heat energies arising from a particle interaction. To be a competitive CENNS detector, the CryoCube array is designed with the following specifications: a low-energy threshold ( ∼ 50 eV), the ability to identify and reject with a high efficiency the overwhelming electromagnetic backgrounds (gamma, beta, and X-rays), and a sufficient payload ( ∼ 1 kg). After a brief introduction of the future Ricochet experiment and its CryoCube, the current works and first performance results on the optimization of the heat channel, and the electrode designs will be presented. We conclude with a preliminary estimation of the CryoCube sensitivity to the CENNS signal within Ricochet. [ABSTRACT FROM AUTHOR]

With applications in cosmology, infrared astronomy and CMB survey, frequency-division multiplexing (FDM) proved to be a viable readout for transition-edge sensors (TESs). We investigate the occurrence of out-of-band resonances (OBR) which could constrain the bandwidth of the FDM readout of TES bolometers. The study includes SPICE modeling of the entire setup including the cryogenic harness, LC filters, Superconducting Quantum Interference Device (SQUID) and room-temperature amplifier. Simulation results show that the long harness (for flight model) could cause multiple reflections that generate repetitive spikes in the spectrum. Peaks of the OBR are mainly due to the parasitic capacitances at the input of SQUID. Implementing a low-pass RC circuit (snubber) at the input of the SQUID dampened the OBR. As a result, the first peak only appears around 20 MHz which is a safe margin for the 1 MHz - 3.8 MHz FDM in use in the prototype readout. Using a spectrum analyzer and broadband LNAs, we also measured the OBR for the prototype FDM readout in the laboratory up to 500 MHz. The measurement was conducted at temperatures of 50 mK and 4 K and for various biasing of the DC SQUID. It turns out that OBRs are more intense at 50 mK and are caused by the harness impedance mismatch rather than the SQUID. Simulation codes and supporting materials are available at https://github.com/githubamin/LT-Spice-Simulation-of-FDM-readout. [ABSTRACT FROM AUTHOR]

Coherent elastic neutrino-nucleus scattering (CE ν NS) offers a valuable approach in searching for physics beyond the Standard Model. The Ricochet experiment aims to perform a precision measurement of the CE ν NS spectrum at the Institut Laue-Langevin nuclear reactor with cryogenic solid-state detectors. The experiment will employ an array of cryogenic thermal detectors, each with a mass of around 30 g and an energy threshold of 50 eV. One section of this array will contain 9 Transition Edge Sensor (TES)-based calorimeters. The design will not only fulfill requirements for Ricochet, but also act as a demonstrator for future neutrino experiments that will require thousands of macroscopic detectors. In this article, we present an updated TES chip design, as well as performance predictions based on a numerical modeling. [ABSTRACT FROM AUTHOR]

To improve the responsivity of terahertz (THz) antenna-coupled bolometer, heater (load) resistance has to be increased to suppress the thermal conduction and realize larger temperature rise of the thermistor. Proper design of antenna is therefore essential to assure the impedance matching between antenna and heater. From this viewpoint, a high-impedance folded-dipole antenna (FDA) has been studied numerically by the finite element simulation. The effect of FDA structural parameters such as number of arms, antenna width, and arm spacing are discussed with the lumped port and resistive heater coupled to the antenna gap for the cases of radiating and receiving modes, respectively. The product of resonant resistance and area efficiency is used to predict the improvement made by FDA as a figure of merit (FOM) correlated to the bolometer responsivity. This study revealed that the optimum FOM in FDA-coupled bolometer operating at 1 THz was obtained with three arms, 1- $\mu \text{m}$ antenna width and 4- $\mu \text{m}$ arm spacing. A comparison was made with the result from a half-wave dipole antenna and revealed that FDA could enhance the bolometer responsivity by a factor of 15. This research demonstrated the effectiveness of the FDA to improve the performance of THz antenna-coupled bolometer for applications such as imaging for non-destructive inspection.

The excellent performance of bolometers in the infrared and terahertz regions has attracted great attention. Understanding the transport process of charged particles is an efficient approach to determine detector performance. However, the lack of studies on the fine‐scale spatial motion of microscopic particles in bolometers has prevented a full understanding of the physical process. Herein, using micro‐nano‐scale optoelectronic performance correlation measurements, it is described how prevalent defect states at the grain boundaries (GBs) decrease current responses. Ions at the GBs of the polycrystalline perovskite bolometer contribute to the photocurrent via thermal excitons. In addition, the built‐in electric field established by ion migration fluctuates periodically with the strength of the light‐heating process due to the interaction between the bolometric effect and the Coulomb force. Additionally, the first ion‐bolometric detector is demonstrated with a significant photovoltage response to infrared and THz waves (75.3 kV W−1 at 1064 nm and 2.3 kV W−1 at 0.22 THz). An examination of the THz images shows the potential for large‐area THz imaging applications. The ion‐bolometric effect combines the broad spectral characteristics of the bolometer effect with the temperature sensitivity due to ion migration and provides a unique perspective on detector technology. [ABSTRACT FROM AUTHOR]

It is known that the dielectric layer (resonator) located behind the conducting plate of the bolometer system can significantly increase its sensitivity near the resonance frequencies. In this paper, the possibility of receiving broadband electromagnetic signals in a multilayer bolometric meta-material made of alternating conducting (e.g., silicon semiconductor) and dielectric layers is demonstrated both experimentally and numerically. It is shown that such a multilayer structure acts as a lattice of resonators and can significantly increase the width of the frequency band of efficient electromagnetic energy absorption. The parameters of the dielectric and semiconductor layers determine the frequency bands. Numerical modeling of the effect has been carried out under the conditions of our experiment. The numerical results show acceptable qualitative agreement with the experimental data. This study develops the previously proposed technique of resonant absorption of electromagnetic signals in bolometric structures.

We present an uncooled high-sensitivity bolometric terahertz detector by incorporating plasmonic absorbers and transducer beams made of phase changing materials. We present a comprehensive design parameter analysis of the bolometer device—from electromagnetic absorption to thermal and mechanical analysis. Our design integrates plasmonic absorber and vanadium dioxide (VO2) beams biased at transition temperature to achieve ultra-high temperature coefficient of resistance. The beams are positioned in proximity to plasmonic hot spots created by radiation absorption. Such integration simultaneously allows spectrum selectivity and tunability in radiation absorption across a wide band in the THz regime as well as high-sensitivity detection by a small-footprint device. The design additionally facilitates simultaneous sensing of intensity and polarization of incident radiation by utilizing polarization-dependent plasmonic field enhancement. We estimate a responsivity over 5 kV·W−1, noise equivalent power (NEP) below 12 pW, and normalized detectivity over 108 cm·Hz1/2·W−1 which are competitive to state-of-the-art THz bolometer designs. [ABSTRACT FROM AUTHOR]

Superconducting Transition-Edge Sensor (TES) bolometers are used for cosmic microwave background (CMB) observations. We used a testbed to evaluate the thermal performance of TES bolometers in regard to the saturation power P sat and intrinsic thermal time constant τ 0 . We developed an evaluation method that is complementary to methods with electrothermal feedback. In our method, the antenna termination resistor of the bolometer is directly biased with DC or AC electric power to simulate optical power, and the TES is biased with small power, which allows P sat and τ 0 to be determined without contribution from the negative electrothermal feedback. We describe the method and results of the measurement using it. We evaluated P sat of five samples by applying DC power and confirmed the overall trend between P sat and the inverse leg length. We evaluated τ 0 of the samples by applying DC plus AC power, and the measured value was reasonable in consideration of the expected values of other TES parameters. This evaluation method enables us to verify whether a TES has been fabricated with the designed values and to provide feedback for fabrication for future CMB observations. [ABSTRACT FROM AUTHOR]

High-impedance surfaces (HIS) are investigated here for the above-IC integration of sub-millimeter-wave (350 µm here) detectors on CMOS electronics using standard thin film manufacturing processes and materials. We demonstrate theoretically and experimentally the efficient optical absorption of a resistive dipole array above an HIS at cryogenic temperature. More specifically, an absorption above 78% in linear polarization is obtained over a bandwidth of 100 µm around a center wavelength of 350 µm. These results confirm the promising performances of HIS structures in the perspective of future polarimetric bolometers in terms of absorption efficiency, bandwidth and cross-polarization discrimination. [ABSTRACT FROM AUTHOR]

Requirements are considered for the diagnostics of radiation losses, extreme ultraviolet and soft X‑ray emission for tokamak with reactor technologies (TRT). Proposals for the geometric placement, type and number of detectors are presented. The possibility of placing all three diagnostics in the same poloidal cross section of the tokamak is discussed. [ABSTRACT FROM AUTHOR]

• Correlation between the electrical and the magnetic properties was proposed. • At low temperatures, conduction was described by the electron-magnon interaction. • At high temperatures, conduction was explained by the thermal activation model. • A percolation model was used to describe the conduction for all temperature range. • The PMSC/FMM transition temperature, increases with the external magnetic field. In this research work, we investigated the correlation between the electrical and magnetic properties of the superparamagnetic compound La 0.6 Ca 0.4 MnO 3 (S 0 C 1) prepared by the citric-gel method. The confrontation of the experimental data with the theoretical models revealed that the conduction at low temperatures, in the ferromagnetic metallic (F M M) phase, can be mainly described by electron–electron (e - e) and electron-magnon (e - m) interactions. The contribution of the (e - m) interaction, became weak for strong magnetic fields. At high temperatures, in the paramagnetic semiconductor (P M S C) phase, the thermally activated hopping (T A H) model proved to be the most appropriate to fit the experimental data. To describe the resistivity behavior in a wide temperature range including the phase transition region between the (F M M) and (P M S C) phases, we adopted the percolation model, based on the phase segregation mechanism. [ABSTRACT FROM AUTHOR]

Feedhorn- and orthomode transducer- (OMT) coupled transition edge sensor (TES) bolometers have been designed and micro-fabricated to meet the optical specifications of the LiteBIRD high frequency telescope (HFT) focal plane. We discuss the design and optical characterization of two LiteBIRD HFT detector types: dual-polarization, dual-frequency-band pixels with 195/280 GHz and 235/337 GHz band centers. Results show well-matched passbands between orthogonal polarization channels and frequency centers within 3% of the design values. The optical efficiency of each frequency channel is conservatively reported to be within the range 0.64 - 0.72, determined from the response to a cryogenic, temperature-controlled thermal source. These values are in good agreement with expectations and either exceed or are within 10% of the values used in the LiteBIRD sensitivity forecast. Lastly, we report a measurement of loss in Nb/SiN x /Nb microstrip at 100 mK and over the frequency range 200–350 GHz, which is comparable to values previously reported in the literature. [ABSTRACT FROM AUTHOR]

Experiments deploying large arrays of transition-edge sensors (TESs) often require a robust method to monitor gain variations with minimal loss of observing time. We propose a sensitive and non-intrusive method for monitoring variations in TES responsivity using small square waves applied to the TES bias. We construct an estimator for a TES's small-signal power response from its electrical response that is exact in the limit of strong electrothermal feedback. We discuss the application and validation of this method using flight data from SPIDER, a balloon-borne telescope that observes the polarization of the cosmic microwave background with more than 2000 TESs. This method may prove useful for future balloon- and space-based instruments, where observing time and ground control bandwidth are limited. [ABSTRACT FROM AUTHOR]

The integration of low-dimensional materials with optical waveguides presents promising opportunities for enhancing light manipulation in passive photonic circuits. In this study, we investigate the potential of aerosol-synthesized single-walled carbon nanotube (SWCNT) films for silicon nitride photonic circuits as a basis for developing integrated optics devices. Specifically, by measuring the optical response of SWCNT-covered waveguides, we retrieve the main SWCNT film parameters, such as absorption, nonlinear refractive, and thermo-optic coefficients, and we demonstrate the enhancement of all-optical wavelength conversion and the photoresponse with a 1.2 GHz bandwidth.

The doubly clamped microelectromechanical system (MEMS) beam resonators exhibit extremely high sensitivity to tiny changes in the resonance frequency owing to their high quality (Q-) factors, even at room temperature. Such a sensitive frequency-shift scheme is very attractive for fast and highly sensitive terahertz (THz) detection. The MEMS resonator absorbs THz radiation and induces a temperature rise, leading to a shift in its resonance frequency. This frequency shift is proportional to the amount of THz radiation absorbed by the resonator and can be detected and quantified, thereby allowing the THz radiation to be measured. In this review, we present an overview of the THz bolometer based on the doubly clamped MEMS beam resonators in the aspects of working principle, readout, detection speed, sensitivity, and attempts at improving the performance. This allows one to have a comprehensive view of such a novel THz detector.

We report on the development of scintillating bolometers based on lithium molybdate crystals that contain molybdenum that has depleted into the double-β active isotope 100Mo (Li2100deplMoO4). We used two Li2100deplMoO4 cubic samples, each of which consisted of 45-millimeter sides and had a mass of 0.28 kg; these samples were produced following the purification and crystallization protocols developed for double-β search experiments with 100Mo-enriched Li2MoO4 crystals. Bolometric Ge detectors were utilized to register the scintillation photons that were emitted by the Li2100deplMoO4 crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc Underground Laboratory (Spain). We observed that the Li2100deplMoO4 scintillating bolometers were characterized by an excellent spectrometric performance (∼3–6 keV of FWHM at 0.24–2.6 MeV γs), moderate scintillation signal (∼0.3–0.6 keV/MeV scintillation-to-heat energy ratio, depending on the light collection conditions), and high radiopurity (228Th and 226Ra activities are below a few µBq/kg), which is comparable with the best reported results of low-temperature detectors that are based on Li2MoO4 using natural or 100Mo-enriched molybdenum content. The prospects of Li2100deplMoO4 bolometers for use in rare-event search experiments are briefly discussed.

Terahertz (THz) electromagnetic waves are attractive for use in nondestructive and biocompatible sensing applications. Thermal sensors are widely used for THz detection owing to the small photon energies of THz radiation, where this requires materials with low thermal conductivity and a small heat capacity to ensure the sensitive and fast operation of the sensors. In this study, we investigated the thermal and optical properties of porous nanomesh structures for sensitive THz bolometric detection. Nanometer (nm)-scale hole array structures were formed on gallium arsenide (GaAs) microelectromechanical system (MEMS) beams to improve their thermal properties. The thermal conductance of the porous MEMS beams was obtained by measuring their thermal bandwidths; it was found to decrease by as much as ~90% when the porosity (P) of the porous nanostructure was increased to ~0.69. We also measured the THz absorptance of the porous hole array structure. The results show that although the porous nanostructure has a much smaller area than the bulk material, it maintained a high coefficient of THz absorptance because the featured size was much smaller than the THz wavelength. The measured absorptance agreed well with that calculated by using the Drude model. These results demonstrate that the porous nanomesh structure is promising for developing highly sensitive THz thermal sensors. [ABSTRACT FROM AUTHOR]

Near-infrared detection is widely used for nondestructive and non-contact inspections in various areas, including thermography, environmental and chemical analysis as well as food and medical diagnoses. Common room temperature bolometer-type infrared sensors are based on architectures in the ÎĽ m range, limiting miniaturization for future highly integrated ‘More than Moore’ concepts. In this work, we present a first principle study on a highly scalable and CMOS compatible bolometer-type detector utilizing Ge nanowires as the thermal sensitive element. For this approach, we implemented the Ge nanowires on top of a low thermal conducting and highly absorptive membrane as a near infrared (IR) sensor element. We adopted a freestanding membrane coated with an impedance matched platinum absorber demonstrating wavelength independent absorptivity of 50% in the near to mid IR regime. The electrical characteristics of the device were measured depending on temperature and biasing conditions. A strong dependence of the resistance on the temperature was shown with a maximum temperature coefficient of resistance of âˆ'0.07 Kâˆ'1 at T  = 100 K. Heat transport simulations using COMSOL were used to optimize the responsivity and temporal response, which are in good agreement with the experimental results. Further, lock-in measurements were used to benchmark the bolometer device at room temperature with respect to detectivity and noise equivalent power. Finally, we demonstrated that by operating the bolometer with a network of parallel nanowires, both detectivity and noise equivalent power can be effectively improved. [ABSTRACT FROM AUTHOR]

The design of low temperature bolometric detectors for rare event searches necessitates careful selection and characterization of structural materials based on their thermal properties. We measure the thermal conductivities of polytetrafluoroethylene (PTFE) and Al2O3 ceramic (alumina) in the temperature ranges of 0.17–0.43 K and 0.1–1.3 K, respectively. For the former, we observe a quadratic temperature dependence across the entire measured range. For the latter, we see a cubic dependence on temperature above 0.3 K, with a linear contribution below that temperature. This paper presents our measurement techniques, results, and theoretical discussions.

• This paper presents the design and computational analysis of the bolometer camera for the MT-I spherical tokamak. The estimation of the line of sight (LOS) and field of view (FOV) of the AXUV system. • Optimization of the aperture by signal-to-noise ratio method and estimation of geometrical etendue. The computation of plasma emissivity distribution using impurity densities and their cooling rates. • The computation of power incident on the photodiode array and signal-to-noise ratio (SNR). The MT-I is a spherical tokamak at the Pakistan Tokamak Plasma Research Institute, and has a major radius of 15 cm and a minor radius of 9 cm. This paper presents the design and computational analysis of the Absolute eXtreme Ultra-Violet (AXUV) photodiode-based bolometer camera, which will be used for the first time in the MT-I tokamak. The bolometer camera contains a single array of 16 AXUV photodiodes placed behind an aperture to compute the line of sight (LOS) and field of view (FOV) of the system. This array is located at the midplane of the vessel, which provides a radial resolution of about 16 mm. The individual FOV of each photodiode and the collective FOV of the array are 4.1° and ±34.5°, respectively. The impurity densities and their cooling rates for elements like carbon, oxygen, and iron are used to compute the plasma emissivity distribution, the power incident on the photodiode array, and signal-to-noise ratio (SNR) analysis. The analysis reveals that the radiated power loss is about 10 % of the ohmic heating input power. The geometrical etendue falls within the range of 2.2 × 10−5 to 3.2 × 10−5 Sr cm2. The bolometer exhibits a frequency response bandwidth of 10 kHz, and its temporal resolution is around 0.1 milliseconds. [ABSTRACT FROM AUTHOR]

Infrared antennas with reconfigurable characteristics offer several advantages in the medical, military, telecommunication and energy harvesting areas, while their design and implementation is a particularly challenging task for the researchers. This paper proposes a pixel antenna, designed for mid-infrared frequencies with a bandwidth more than 25 THz, consisting of 3 × 3 square metallic planar patches. Bolometer-based switches are placed between the adjacent pixels in order to obtain the adaptable characteristics, optimized for the incoming infrared radiation. The incident wave from a certain direction will heat up the bolometers. Consequently, the conductivity of these bolometers (PTC) will be decreased, and as a result they can be considered to turn to OFF state. The simulation results suggest that the proposed structure can steer the antenna pattern toward the direction of the incident radiation in an adaptable manner, thereby considerably increasing the antenna gain. The gain of the antenna can be increased up to 2 dB with respect to the reference one, which makes it a promising structure for various applications. [ABSTRACT FROM AUTHOR]

Transportasi udara merupakan salah satu moda transportasi dengan peningkatan jumlah penumpang yang signifikan. Namun, dalam perkembangannya moda ini rawan aksi terorisme dan sabotase, yang sebagian besar disebabkan oleh kelalaian dalam mendeteksi barang logam berbahaya. Gelombang THz dapat digunakan sebagai pencitraan karena aman, memiliki resolusi spasial yang tinggi, tetapi rentan akan efek difraksi. Pada makalah ini dilakukan studi difraksi dan simulasi pencitraan logam gelombang THz dengan perangkat lunak CST Microwave Studio. Sensor yang digunakan dalam simulasi adalah antena bowtie terkopel bolometer karena desainnya yang sederhana dan bandwith yang lebar. Simulasi dilakukan dengan variasi jenis antena yang memiliki frekuensi kerja 1 THz, 3 THz, dan 5 THz. Variasi jenis polarisasi plane wave - polarisasi Ex & Ey juga dilakukan untuk masing-masing jenis antena. Simulasi dengan peningkatan frekuensi menghasilkan citra yang lebih akurat karena memiliki efek difraksi yang lebih kecil dan resolusi spasial yang lebih besar. Simulasi dengan polarisasi Ex menghasilkan citra yang lebih baik dalam kontras karena memiliki arah pergerakan medan listrik yang sejajar dengan sensor yang digunakan.

POLARBEAR-2 (PB-2) is a cosmic microwave background (CMB) polarization experiment that will be located in the Atacama highland in Chile at an altitude of 5200 m. Its science goals are to measure the CMB polarization signals originating from both primordial gravitational waves and weak lensing. PB-2 is designed to measure the tensor to scalar ratio, r, with precision σ(r) > 0:01, and the sum of neutrino masses, Σmz, with σ(Σmv) < 90 meV. To achieve these goals, PB-2 will employ 7588 transition-edge sensor bolometers at 95 GHz and 150 GHz, which will be operated at the base temperature of 250 mK. Science observations will begin in 2017.