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Many improvements are required to bring quantum key distribution (QKD) from the laboratory to the commercial market, such as simplifying structure and enhancing stability. In this letter, a QKD module based on planar lightwave circuit (PLC) has been proposed. The chip inside module is based on silica-silicon material and composed of various optical splitter, asymmetric Mach–Zehnder interferometer and directional coupler. The module can allow users adjust temperature stably. The interference visibility can be high to 96% merely by controlling and stabilizing temperature and voltage of the module through self-interfering method which showed its potential in practical application. [ABSTRACT FROM AUTHOR]

In this article, the design, implementation, and characterization of a micro-oven-controlled dual-mode piezoelectric microelectromechanical system (MEMS) resonator are presented. The designed MEMS resonator simultaneously operates in the width extensional (WE) mode and length shear (LS) mode. Both modes show high quality factor (${Q}$). The measured ${Q}$ is 15672 for the WE mode and 17781 for the LS mode. Taking advantage of the significant difference in frequency–temperature characteristics between the two modes, accurate temperature sensing and precisely closed-loop micro-oven control are implemented by phase locking the MEMS resonator at an oven-set temperature. In-plane micro-oven is composed of four folded beams and an isolation frame, which maintains an extremely uniform temperature distribution on the resonating element. The micro-oven structure requires less than 7.8 mW to maintain the resonator’s temperature at the preset temperature over variations in the external temperature range of −40 °C to 80 °C. Measured real-time frequency stability of the reported micro-oven-controlled MEMS resonator is less than ±400 ppb over a wide temperature range from −40 °C to 80 °C. [ABSTRACT FROM AUTHOR]

The development of 5G has put forward a higher demand for filters, and the purpose of this work is fabricating surface acoustic wave (SAW) filters with excellent temperature stability and high power handling using LiTaO3/SiC bonded wafers. SAW resonators with different wavelengths are fabricated on LiTaO3/SiC, and LiTaO3/Si, bulk LiTaO3 as well. We evaluate these resonators, concluding that the bilayer substrates can enhance the performance. Subsequently, SAW filters are designed and fabricated. For the filters based on LiTaO3/SiC, the center frequency is around 2.62 GHz and the minimum insertion loss is 1.90 dB. The whole passband is flat and larger than 200 MHz, and the return loss is larger than 10 dB. SiC is more effective than Si in the enhancements of temperature stability and power handling. SiC reduces the temperature coefficient of the frequency at the left side of the passband to about half of that on LiTaO3/Si and one-sixth of that on bulk LiTaO3, and enlarges the peak power handling to 35.7 dBm. The time-to-failure of the filters on LiTaO3/SiC is 3.8 times as long as LiTaO3/Si and 11.3 times the level of bulk LiTaO3, when an input power of 30 dBm is applied ceaselessly. This work demonstrates the potential of SAW filters based on LiTaO3/SiC for RF filters in 5G. [2021-0233] [ABSTRACT FROM AUTHOR]

Recently, dielectric energy storage materials and devices attracted much research interest due to its high-power density and the resulted applications. In this work, relaxor ferroelectric (Pb 1-x ,La x)(Zr 0.65 ,Ti 0.35)O 3 (abbreviated as PLZT100X, X = 0.06, 0.08, 0.10 and 0.12) thin films are deposited on Pt/Ti/SiO2/Si substrates by a sol-gel method, and temperature stability of relative dielectric constant as well as energy storage density of the PLZT thin films with different level of La doping are studied. The relative dielectric constant of the PLZT10 thin films is 873 at 1 kHz at 30°C, with maximum of variation of 7.6% in the temperature range from 30–200 °C, which indicates very high temperature stability. The energy storage density of the PLZT thin films is 38.8 J/cm3, 42.2 J/cm3, 33.5 J/cm3 and 36.0 J/cm3 with the La doping of 0.06, 0.08, 0.10 and 0.12, respectively, under the applied electric field of 2840 kV/cm. The energy efficiency of the PLZT thin films is above 70%. In addition, the energy storage density of the PLZT thin films shows good temperature stability, with about 20 J/cm3around the electric field of 1800 kV/cm in the temperature range from 30–150 °C. [ABSTRACT FROM AUTHOR]

A single-trim, highly accurate Colpitts-based frequency reference is presented. Our analysis shows that the Colpitts-topology outperforms the cross-coupled LC-topology in terms of temperature stability. Measurements on prototypes in a 0.13- $\mu \text{m}$ high-voltage CMOS silicon on insulator (SOI) process were carried out from −50 °C to 170 °C. Based on sample-specific single room temperature trim and batch calibration, our frequency reference achieves an accuracy of ±120 ppm for 16 samples from a single wafer utilized for extracting the batch-calibration polynomial and ±300 ppm for 48 samples across three wafers from the same batch. This is a 4 $\times $ improvement over related single-trim state-of-the-art solutions. Frequency drift due to aging, tested after a six-day 175 °C storage, is below 100 ppm. The oscillator core dissipates 3.5 mW from a 2.5-V supply and has 220-ppm/V supply sensitivity without supply regulation. [ABSTRACT FROM AUTHOR]

The rapid development of the fifth-generation (5G) wireless system is driving strong demand for high-performance radio frequency filters. This work studies shear horizontal surface acoustic wave (SAW) devices using 15°-rotated Y-cut X-propagating (15°Y-X) LiNbO3/SiO2/SiC multilayered substrates. Single-crystalline 15°Y-X LiNbO3 films are bonded to SiO2/SiC handling substrates by the smart cut technology. On the basis of accurate finite-element-method simulations, LiNbO3/SiO2/SiC wafer configurations are optimized to suppress spurious resonance due to Rayleigh-mode and transverse-mode responses, and one-port resonators with a clean spectrum, a high electromechanical coupling coefficient of 22.00%, and an admittance ratio (impedance ratio) over 65 dB are successfully implemented. Based on the characteristics of the resonators, high-performance filters with a center frequency of 1.28 GHz, a large 3-dB fractional bandwidth of 16.65%, and a low minimum insertion loss of 1.02 dB are successfully designed and fabricated. Furthermore, no ripples in the passband of the filters are observed. Additionally, the filters exhibit a temperature coefficient of center frequency of −63.8 ppm/°C and a large power durability of 33.2 dBm. This work confirms the high performances of the SAW devices using the 15°Y-X LiNbO3/SiO2/SiC multilayered substrate, and this type of SAW device exhibits a prospect of commercial applications in the 5G wireless system. [ABSTRACT FROM AUTHOR]

In this paper, we report a novel honeycomb-like disk resonator gyroscope (HDRG) and its comprehensive test results. HDRG inherits many advantages from traditional nested-ring disk resonator such as axisymmetric structure and huge capacitive area. In addition, HDRG owns unique characteristics and potentials due to its topology structure, namely, higher immunity to fabrication errors, better resonant mode consistency and better inner electrode arrangement. This new design of HDRG is based on a tradeoff between performance parameters including quality factor, decaying time constant, effective mass, effective capacitive area, transducer sensitivity and mechanical noise. The characteristics and potentials of HDRG are investigated firstly. Afterwards, the parameter optimization and frame structure optimization of HDRG are investigated. Based on the investigation, a novel HDRG is proposed. A prototype of this design is fabricated and its overall performance is tested. Results show that the quality factor of HDRG increases from 81.1k to 171.6k and the decaying time constant increases from 1.507 s to 6.973 s. The bias instability of the gyroscope reaches 0.11 °/h at room temperature without any compensation, more than eighty times smaller than the former design, exhibiting significant performance improvement. Moreover, ranging from −40 °C to 60 °C, the temperature coefficient of scale factor is 0.188%/ °C, and the maximum variations of zero offset and bias instability over temperature are 40 °/h and 0.12 °/h respectively, showing good robustness to environment disturbance. This new gyroscope has the potential to operate steadily under variable temperature conditions, offering as a new type of MEMS gyroscope with high performance and good robustness. [ABSTRACT FROM AUTHOR]

Ring touch mode capacitive pressure sensor, characterized by ring stopper and stepped circular diaphragm, is developed to eliminate or greatly alleviate some disadvantages existing in conventional or small-area touch mode capacitive pressure sensor. An electrothermomechanical coupling model is developed to calculate the deformation, stress and so on of the diaphragm, and it is universally available for different touch modes and non-touch mode. The model is with rapid calculation speed and it is verified by a combination of the finite element method (FEM) and boundary element method (BEM). Benefiting from the high calculation speed of the model, optimization designs of the sensor are carried out. By adjusting the height dimensions or radial dimensions, high sensitivity and strength can be achieved by such a sensor in different pressure ranges of interest without changing its planar package size and masks, or achieved in a very wide pressure range by an array composed of such sensors with a same set of process parameters of each sensor. On the other hand, optimal ratios of height dimensions or radial dimensions are acquired, which can suppress significantly the temperature’s influence on sensor operation, and furthermore, the optimal ratios are advisable for different pressure ranges and different material parameters of the sensor. [ABSTRACT FROM AUTHOR]

A closed-loop capacitance sensing and control mixed-signal CMOS circuit with a dedicated sensor electrode and a proportional-integral controller was designed to have a sensitivity of 1 fF, a settling time of $200~\mu \text{s}$ , and a voltage capacity of 150 V. In a hybrid integration with a MEMS varactor, the control circuit could switch the varactor capacitance from 270 to 365 fF in 15 ms and hold it within ±2% between 25 °C and 80 °C. Furthermore, using the varactor as the tuning element of a substrate-integrated-waveguide (SIW) resonator, the control circuit could tune its resonance frequency from 33.2 to 33.9 GHz while keeping it within ±0.08% over a temperature range of 25 °C–90 °C. The control circuit occupied an area of 1.7 mm2 and consumed 6 mW. The present closed-loop-controlled MEMS-tunable resonators could be used in a quartz SIW multi-pole filter to realize tunable, small, light, low-cost, robust, and reliable millimeter-wave filters that are critical to 5G and other future-generation communication and radar systems. [ABSTRACT FROM AUTHOR]

We developed a novel method to fabricate Zr-doped ZnO (ZrZnO) thin films via low-temperature atomic layer deposition technique. ZrZnO films were deposited by diethylzinc (DEZ)/tetrakiszirconium (TDMAZr)/H2O cycles instead of the traditional DEZ/H2O/TDMAZr/H2O cycles and applied in thin-film transistors (TFTs). It is found that ZrZnO-TFTs with a Zn-Zr-O:ZnO atomic ratio of 1:49, i.e., ZrZnO (1:49) exhibit excellent properties, such as a minimum subthreshold swing value of 0.37 V/dec, a maximum ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ value of $2.4\times 10^{{7}}$ , a largermobility of 12.38 cm2/ $\text {V}\cdot \text {s}$ , and a smaller threshold voltage shift ($\Delta {V}_{\text {th}}$) of 0.61 V under temperature stress from 25 °C to 105 °C, which are superior compared with TFTs with ZnO channel doped by ZrO2 layer. The stability of ZnO TFTs was improved greatly by Zr-Zn-O doping. Moreover, the field-effect mobility of ZrZnO-TFTs was rarely influenced. Temperature-stress test was carried out to build up the correlation model in terms of the defect structures, subgap states, and stability. These results could provide a newaccess to understand the device instability of ZrZnO TFTs. [ABSTRACT FROM AUTHOR]

Coupled silicon ring resonator filters offer high-order spectral features such as steep roll-offs, high extinction ratios, and wide pass-bands, which are attractive to many applications in telecommunications and quantum computing systems. However, so far, their sensitivity to fabrication and temperature variations have limited the usability of such filters in practical applications. Here, by using in-resonator photoconductive heaters (IRPHs) to both sense and tune the resonance conditions of ring resonators, we demonstrate automatic configuration and wavelength locking of multiring resonator filters to an input laser's wavelength. We demonstrate the automatic configuration of a four-ring Vernier filter across a 36.7-nm wavelength range spanning the entire C-band and the wavelength locking of the same filter to counteract a practical chip temperature variation of 65 °C. As IRPHs do not require additionalmaterial depositions, photodetectors, or power taps and use the same contact pads for both the sense and the tune operations, these results are achieved without compromising the cost or area of the devices. Furthermore, by localizing the feedback loops to only rely on the resonance conditions of adjacent rings, we present a tuning algorithm in which the number of iterations scales linearly with the number of coupled rings in the system. As this method does not rely on the output spectral shape of the system, it is, in general, applicable to a wide range of coupled resonator systems. Our results pave a path toward practical deployment of high-order and large-scale silicon ring resonator systems. [ABSTRACT FROM AUTHOR]

A low-cost method to adjust the mirror reflectivity of vertical-cavity surface-emitting lasers (VCSELs) helps to optimize the cavity photon lifetime. The joint variation of photon lifetime and the oxide aperture diameter of our 980-nm VCSELs allows optimization procedures between the laser parameters. A new indicator helps to judge the optimum mirror reflectivity to enable increased bit rates in concert with reduced energy consumption, as well as temperature stability, and a smaller bias current density. Error-free back-to-back data transmission at 50 Gb/s over a wide temperature range from 25 °C to 75 °C for completely unchanged driving conditions is presented amongst other progress, including a 400-fJ/b data transmission energy efficiency at 50 Gb/s. [ABSTRACT FROM AUTHOR]

An electrical-thermal co-simulation based on the finite element method is presented for analysis of high-power RF/microwave circuits. The co-simulation integrates a full-wave electromagnetic analysis and a transient thermal analysis through an iterative scheme, and is devised for the design and analysis of RF/microwave circuits operated at high frequencies and high power levels. To enhance the efficiency in solving large-scale problems, a domain decomposition scheme called the finite element tearing and interconnecting and an adaptive time-stepping scheme based on the algorithm of proportional-integral-derivative control are incorporated into the co-simulation. Temperature stability analysis is performed with the proposed co-simulation for a matching network in high-power RF amplifiers and for a substrate integrated waveguide filter. [ABSTRACT FROM PUBLISHER]

Modulation properties and temperature stability of short cavity ridge waveguide lasers based on high-quality InAs quantum dots exhibiting a total modal gain of \sim 90 cm ^{-1} are reported. The 338- \mu \text{m}$ -long lasers show a threshold current of 20 mA at room temperature and an output powers of up to 36 mW. A maximum small signal modulation bandwidth of 15 GHz was obtained at 14 °C, which degrades to 13 GHz at 60 °C and 8 GHz at 80 °C. Digital modulation at 25 Gb/s between 15 °C and 50 °C was obtained with clear open eyes under constant drive conditions (dc and ac). The maximum data rates of 32 and 35 Gb/s were obtained for 338- and 230- \mu \text{m} -long lasers, respectively, at 14 °C. [ABSTRACT FROM PUBLISHER]

A fully-integrated 18.5 kHz RC time-constant-based oscillator is designed in 65 nm CMOS for sleep-mode timers in wireless sensors. A comparator offset cancellation scheme achieves $4\times $ to $25\times $ temperature stability improvement, leading to an accuracy of ±0.18% to ±0.55% over −40 to 90 °C. Sub-threshold operation and low-swing oscillations result in ultra-low power consumption of 130 nW. The architecture also provides timing noise suppression, leading to $10\times $ reduction in long-term Allan deviation. It is measured to have a stability of 20 ppm or better for measurement intervals over 0.5 s. The oscillator also has a fast startup-time, with the period settling in 4 cycles. [ABSTRACT FROM PUBLISHER]

Effects of partial substitution of Ce for didymium (Pr–Nd alloy, abbreviated to Di) on elevated temperature magnetic properties in sintered (Di1–xCex)27.5Dy3Al0.1Cu0.1Febal.B (wt.%, x=0~\sim ~0.56 ) magnets were investigated in this paper. Temperature stability of remanence was found to decrease in Ce substitution. However, the temperature stability of coercivity was largely improved when x\geqslant 0.24 . Temperature dependence of magnetocrystalline anisotropy field ( H_{A}) was improved as Ce substitution. Microstructural observation and micromagnetic analysis indicated that a microstructure of magnets was modified when x\geqslant 0.24$ . The enhancement of temperature stability of coercivity was due to the improvement of temperature dependence of H_{A} and the modification of microstructure. [ABSTRACT FROM AUTHOR]

Ring oscillator (RO)-based physical unclonable function (PUF) is resilient against noise impacts, but its response is susceptible to temperature variations. This paper presents a low-power and small footprint hybrid RO PUF with a very high temperature stability, which makes it an ideal candidate for lightweight applications. The negative temperature coefficient of the low-power subthreshold operation of current starved inverters is exploited to mitigate the variations of differential RO frequencies with temperature. The new architecture uses conspicuously simplified circuitries to generate and compare a large number of pairs of RO frequencies. The proposed nine-stage hybrid RO PUF was fabricated using global foundry 65-nm CMOS technology. The PUF occupies only 250~ \mu \textm^ 2 of chip area and consumes only 32.3~ \mu \textW per challenge response pair at 1.2 V and 230 MHz. The measured average and worst-case reliability of its responses are 99.84% and 97.28%, respectively, over a wide range of temperature from −40 to 120 °C. [ABSTRACT FROM PUBLISHER]

We demonstrate compact optically pumped microsquare cavity laser on InP-based multiple-quantum-wells material platform. Continuous-wave operation is achieved for microsquare cavity with footprint as small as 4 × 4 μm2. Numerical mode analysis and experimental characterization of the microsquare laser are conducted, and the results are compared with the commonly used microdisk cavity laser fabricated on the same platform. The microsquare laser shows a lower lasing threshold and infers a higher differential efficiency than the microdisk counterpart. The microsquare cavity laser has also sufficiently high quality factor, and higher pumping injection efficiency due to the more evenly distributed field profile as compared to that of the microdisk. Experimental result also shows that the microsquare laser has better temperature stability than the microdisk. These results promise a potential alternative laser structure for on-chip light source applications. [ABSTRACT FROM PUBLISHER]

This paper presents unreleased CMOS-integrated MEMS resonators fabricated at the transistor level of IBM's 32SOI technology and realized without the need for any postprocessing or packaging. In this technology, resonant body transistors (RBTs) are driven capacitively and sensed piezoresistively using an n-channel field effect transistor (FET). Acoustic Bragg Reflectors (ABRs) are used to localize acoustic vibrations in the unreleased resonators completely buried under the CMOS metal stack and surrounded by low-κ dielectric. FET sensing is analytically compared with alternative active and passive sensing mechanisms to benchmark CMOS-MEMS resonator performance with frequency scaling. Experimental results from the first generation hybrid CMOS-MEMS RBTs show RBTs operating above 11 GHz with Qs of 24-30 and footprints of 5 × 3 μm. Comparative behavior of devices with design variations is used to demonstrate the effect of ABRs on spurious mode suppression. In addition, the performance of the RBTs is compared with passive electrostatic resonators, which show no discernible peak. Finally, temperature stability of <;3 ppm/K due to complimentary materials in the CMOS stack is analytically and experimentally verified. [ABSTRACT FROM AUTHOR]

A novel TM01 monoblock dielectric filter is presented in this paper. The proposed filter is made from a single piece of ceramic with silver-plated external surfaces and a metallic lid for hosting tuning screws. The dominant TM01 mode is supported by a centered dielectric rod with one end short-circuited. Not requiring a metallic housing and dielectric resonator mounting fixture, the filter maximizes the space utilization, achieves an optimal Q factor for a given volume, and provides a high mechanical and thermal stability. One prototype filter operating at 2.6 GHz with 50-MHz bandwidth is designed, fabricated, and measured. To demonstrate its superiorities in terms of Q factor and thermal stability, a metal coaxial filter of the same size working at the same frequency and bandwidth is fabricated and measured as well. The measured unloaded Q factor of the monoblock dielectric filter and the metal coaxial filter are about 3000 and 1800, respectively. Furthermore, the frequency drift due to temperature change for the proposed monoblock dielectric filter is -\2.7 ppm/^\circC while that of its coaxial counterpart is -\14.2 ppm/^\circC. More detailed design considerations for such monoblock filters are also given. [ABSTRACT FROM AUTHOR]

A novel optical voltage sensor is proposed by the use of single Fresnel rhomb bismuth germanate crystal. The optical sensing unit is only composed of one voltage sensing crystal and two prism polarizers. The distinguished feature is that the voltage sensing crystal is simultaneously used as a Fresnel rhomb quarter waveplate. An optical phase bias of π/2 is produced by two times of total internal reflection of light wave in the sensing crystal itself, thus additional quarter waveplate usually used in conventional voltage sensor can be removed. Besides the compact optical configuration, the proposed voltage sensor demonstrates larger linear measurement range and good temperature stability in experiments. The ac voltage in the range of 2000 V was measured with a nonlinear error <;0.82% and a measurement sensitivity of 2.2 mV/V, and corresponding temperature drift of the output voltage was <;0.9% for ambient temperature change in the range of (-10 ~ +50) °C. [ABSTRACT FROM PUBLISHER]

A fully integrated 52 MHz frequency reference, designed in a 0.35 µm CMOS process, achieves 1.7 ppm frequency temperature accuracy within 0 to 80°C using a nonlinear compensation technique. The proposed low TCf0 reference oscillator achieves the lowest reported uncompensated temperature coefficient, i.e., 65.25 ppm/°C, among the integrated frequency references. The output reference frequency is obtained by dividing the differential LC Colpitts oscillator output operating at 1.6 GHz. Oscillator core dissipates 14 mW from 2.5 V. The blocks related to the temperature compensation scheme and the remaining system blocks consume 3 mW and 165 mW from 3.3 V supply, respectively. The measured phase noise of 52 MHz output is –94 dBc/Hz at 10 kHz offset frequency and rms period jitter is 3.2 ps. [ABSTRACT FROM AUTHOR]

The influence of rare earth content on coercivity and temperature stability with dual-alloy method has been investigated. It is found that the coercivity of magnets increases rapidly firstly and then slightly with the increasing of rare earth content from the range of 29.5 wt% to 33.5 wt%. The coercivity and the temperature coefficient of coercivity will get better with rare earth content of 31.5 wt%. The result of magnetic anisotropy field of magnet revealed that it almost has no change with different rare-earth content. Scanning electron microscopy (SEM) and Transmission electron microscope (TEM) revealed that continuous thin layers of Nd-rich phase about 4 nm were found along the grain boundaries in the annealed sample at 31.5 wt% rare earth content, while the grain boundary width of magnet exceeds 8 nm at 33.5 wt%. [ABSTRACT FROM AUTHOR]

Reliability characteristics of ferroelectric thin films (10 nm) based on Si-doped \HfO2 have been investigated with focus on potential memory applications. Extensive retention, imprint, and endurance data for this new type of ferroelectric material are presented for the first time. The variability of reliability characteristics in terms of capacitor annealing temperatures as well as excitation amplitude effects is analyzed. Stable ferroelectric switching behavior can be observed in a wide temperature range from 80 K up to 470 K. Bake tests at 125 ^ \circ\C show almost no retention loss for saturated polarization states up to cumulative testing times of 1000 h. In addition to the same-state retention, opposite-state retention was observed to be equally stable. Traditional imprint behavior of the programmed state occurs after a few hours of baking time, and stable behavior could be verified until the end of the 1000-h retention test. Endurance characteristics of the ferroelectric thin films are shown to depend significantly on the annealing temperature of the capacitors and on the cycling voltage during testing. In thin films which had been annealed at 1000 ^ \circ\C, breakdown at 2 MV/cm limits endurance after \10^8 cycles. A lower annealing temperature of 650 ^ \circ\C could improve the breakdown-limited endurance to \10^10 cycles. [ABSTRACT FROM PUBLISHER]

A novel impedimetric biosensor was microfabricated for the selective and quantitative determination of urea by immobilizing urease onto the 1 cm × 2 cm × 0.5 mm PHB substrate which was patterned with gold interdigitated electrode arrays (IDAs) using a combination of photolithography, etching, and thermal evaporation processes. In this study, urease was covalently immobilized onto the gold IDAs functionalized with 10-carboxyl-1-decanethiol (CDT) and similarly, onto gold IDAs functionalized with CDT-polypropylenimine dotriacontaamine dendrimer (Generation 4.0, DAB-Am-32) for monitoring factors that affect urease immobilization. The response studies were carried out as a function of urea concentration with impedimetric measurements. These two immobilization techniques were introduced to assay for in vitro urea and evaluate the two immobilization technique in terms of their repeatability, linear dynamic range, temperature and pH stability. The CDT-urease biosensor displayed linearity for assayed urea up to 10 mM with a response time (t95) of 2 s and yielded a Km(app) of 0.7 mM, indicating the urease enzyme immobilized using CDT onto the PHB IDA surface had a high affinity to urea. The CDT-DAB-Urease biosensor exhibited a dynamic linear range of 0.10 - 300.0 mM, which represented a 30-fold increase in linear dynamic urea range compared to the biosensor with the CDT-urease. The CDT-DAB-Urease yielded a Km(app) of 2.2 mM, which is not significantly different from that for the native, solution-borne enzyme (3 mM), thereby indicating an affinity to urea. Preliminary results suggest that the coupling of the CDT-DAB immobilization technique with microfabrication technology can offer large scale production of PHB urea biosensor. [ABSTRACT FROM PUBLISHER]

We report on a study of the loss mechanisms in microstructured polymer optical fibers (mPOF), resulting in the fabrication of mPOF with a loss equal to that of commercial polymer optical fibers of 0.16 dB/m at 650 nm, nearing the limit imposed by material absorption. The contributions of confinement loss, macroscopic defects, microbending, and surface roughness are investigated and quantified. The temperature stability of mPOF is also investigated and is dependent on stresses introduced into the fiber during fabrication. A method for achieving stable operation up to 90 °C with a minimal increase in fiber loss is outlined. [ABSTRACT FROM PUBLISHER]

This paper elucidates the stabilities of the dc current gain, ideality factor, and offset voltage against variations in temperature and currents for GaAs-based heterojunction bipolar transistors (HBTs). The InGaP/GaAs HBT markedly reduces the offset voltage and improves the temperature stability of the dc current gain relative to those of AlGaAs/GaAs benchmark devices. The relative insensitivity of the offset voltage in the InGaP/GaA HBT to the temperature is established by comparison with l1GaAs/GaAs counterparts. One of the more intriguing aspects of these two HBTs is the replacement of the A1GaAs emitter with the InGaP emitter to improve the temperature stability of the offset voltage. Specifically, the effect of the base current on the offset voltage is abnormal in these devices. In this paper, the conventional Ebers-Moll model cannot account completely for our observed phenomena. Accordingly, the results herein (improved temperature stability of the offset voltage in the InGaP emitter HBT and the uncommon base current effect in these two devices are interpreted in terms of a physics-based analytical model. A strong consistency existed between the experimental data and the theory. Additionally, some reasonable predictions (not obtained from the measured data) of the specific physically based model are presented. The large-signal model provides a description of device performance that will be of use to device engineers and designers. [ABSTRACT FROM AUTHOR]

Two Moderate Resolution Imaging Spectroradiometer (MODIS) instruments are currently in orbit, making continuous global observations in visible to long-wave infrared wavelengths. Compared to heritage sensors, MODIS was built with an advanced set of onboard calibrators, providing sensor radiometric, spectral, and spatial calibration and characterization during on-orbit operation. For the thermal emissive bands (TEB) with wavelengths from 3.7 to 14.4/zm, a v-grooved blackbody (BB) is used as the primary calibration source. The BB temperature is accurately measured each scan (1.47 s) using a set of 12 temperature sensors traceable to the National Institute of Standards and Technology (NIST) temperature standards. The onboard BB is nominally operated at a fixed temperature, 290 K for Terra MODIS and 285 K for Aqua MODIS, to compute the TEB linear calibration coefficients. Periodically, its temperature is varied from 270 K (instrument ambient) to 315 K in order to evaluate and update the nonlinear calibration coefficients. This paper describes MODIS onboard BB functions with emphasis on on-orbit operation and performance. It examines the BB temperature uncertainties under different operational conditions and their impact on TEB calibration and data product quality. The temperature uniformity of the BB is also evaluated using TEB detector responses at different operating temperatures. On-orbit results demonstrate excellent short-term and long-term stability for both the Terra and Aqua MODIS onboard BB. The on-orbit BB temperature uncertainty is estimated to be 10 mK for Terra MODIS at 290 K and 5 mK for Aqua MODIS at 285 K, thus meeting the TEB design specifications. In addition, there has been no measurable BB temperature drift over the entire mission of both Terra and Aqua MODIS. [ABSTRACT FROM AUTHOR]

The metal–insulator–metal (MIM) capacitors were prepared with Ba0.7Sr0.3TiO3/Cr/Ba0.7Sr0.3TiO3 (BST/Cr/BST) dielectric and Pt electrode. The multilayer BST/Cr/BST was sputtered onto Pt/Ti/SiO2/Si substrate. The presence of nano-Cr interlayer affects the electrical properties of the capacitors. The temperature coefficient of capacitance (TCC) of capacitors with 2 nm Cr is about 69% of that of capacitors without Cr. In a previous work, the formation of the TiO2 secondary phase was found after the BST/Cr/BST dielectrics were annealed at 1023 K in O2 atmosphere for 1 h. It is suggested that the nano-Cr interlayer as a catalyst leads to the TiO2 formation during the annealing in O2 atmosphere. The negative value of TCC of BST can be compensated by the positive TCC of TiO2, and the temperature stability in the dielectric constant can be realized for capacitors with nano-Cr interlayer. The voltage stability of BST is also improved with the insertion of nano-Cr interlayer, and the quadratic coefficient in voltage coefficient of capacitance (VCC) of Pt/BST/Cr(2 nm)/BST/Pt is about 30% of that of the BST capacitor without Cr. The effects of Cr thickness on TCC, VCC, dissipation factor, and leakage current density of Pt/BST/Cr/BST/Pt parallel plate capacitors are investigated. [ABSTRACT FROM PUBLISHER]

In this paper, a comparative study of the gain spectra of quantum-well (QW) and quantum-dot (QD) lasers is presented. We point out the differences between the gain function ofa QD laser and a QW laser and give a qualitative description of the effect that leads to the high wavelength stability of QD lasers. Furthermore, we demonstrate, by means of the gain spectra of an InGaAs and AlInGaAs QD laser, that devices with a high wavelength stability can be manufactured over a wide range of emission energies. The experimentally obtained data are fitted with a theoretical model that describes the gain of a QD ensemble. The characteristic features resulting in the high wavelength stability of QD lasers of 0.072 nm/K are analyzed and discussed. [ABSTRACT FROM AUTHOR]

Main characteristics of broadband helicon isolators for the metric and decametric wave ranges are discussed. With the use of equivalent circuits of the isolator, temperature dependencies of the backward attenuation and forward loss are analyzed. The agreement between the experiment and theory supports the validity of the circuit model. [ABSTRACT FROM AUTHOR]

High-power broadband superluminescent diodes (SLDs) emitting in the 1.2-1.3-μm region are demonstrated using InAs-GaAs quantum dots (QDs). The highest output powers of ∼30-50 mW are achieved using 18 QD layers with p-doped GaAs spacers. At these high powers the device operates in a regime of broad bandwidth (∼100 nm) with a spectral dip of ∼5 dB between two separate peaks originated by the QD ground and excited states. Spectral calculations performed with a traveling-wave rate equation model show excellent agreement with the experimental data and provide design rules for optimizing the output spectrum. SLD characteristics are presented for two different device structures consisting of tilted and bent waveguides. The latter allows the achievement of higher output powers at lower currents. The coherence properties and the temperature characteristics are also discussed in detail. [ABSTRACT FROM AUTHOR]

We demonstrate a new method for measuring transverse stress with 10.2-mum spatial resolution in a fiber Bragg grating sensor, without the use of polarization-maintaining fiber, by combining a four-state polarization analysis with a layer-peeling algorithm. Measurements of the externally induced birefringence agree well with predicted values. We also demonstrate that our measurement is insensitive to temperature changes and spatial gradients, making it ideal for nonisothermal applications. [ABSTRACT FROM PUBLISHER]

When testing complex structures using a deployable guided wave system, the measured signals are often far too complex to directly interpret without a priori knowledge of the geometry of the structure. However, in a structural health monitoring (SHM) scenario, the sensors are permanently attached to the structure and so changes in the system can be monitored by comparison to an earlier baseline measurement, taken when the structure was undamaged. This paper investigates such a system for the SHM of plate-like structures using guided waves. The basis of the system is a distributed array of permanently attached piezoelectric guided wave transducers where pairs of transducers are used in pitch-catch configuration allowing the detection and localization of damage in the plate. It has been observed that the use of a single baseline measurement suffers in the medium to long-term due to the variation of environmental conditions. A key parameter in the instability is the change in the temperature of the test structure. A method of using a database of baselines, termed optimal baseline subtraction (OBS), is described and applied to an experimental SHM system. The objective of this paper is to investigate the suitability and robustness of OBS under varying rates of temperature change and its use in the localization of damage. Results have shown that through the OBS an improvement of up to 20 dB in signal-to-coherent noise ratio may be achieved compared with single baseline subtraction [ABSTRACT FROM PUBLISHER]

Stable microwave oscillators are realized based on high-quality factor resonators, which in turn are realized using acoustic, electromagnetic, and optical technologies. This article provides an overview of close-in carrier phase noise and temperature stability of various oscillators [ABSTRACT FROM PUBLISHER]

This work presents a new temperature-insensitive multipoint strain sensor based on fiber Bragg gratings. A divider circuit at the post detection port compensates for optical power variation and thermal instability induced by the nonflatness of the source spectrum. Experimental results show a measurement resolution of ±0.35 μS and a temperature stability of ±0.005% for no strain (±0.48% for a strain of <400 μS) in an example with two sensing points. A measurement linearity of ±0.17% is estimated in the range 0 to 350 μS with no crosstalk. [ABSTRACT FROM PUBLISHER]

Stability is a major concern of semiconductor-metal-oxide (SMO) gas sensors in practical applications, as they may cause false alarm problems. Ambient temperature is a major factor affecting the SMO gas sensor's stability. In this paper, we use a novel way to improve temperature stability of SMO (tin oxide) gas sensors by applying a temperature feedback control circuits which are compatible with our microelectromechanical systems sensor fabrication. A built-in platinum temperature sensor can precisely detect the sensor's working temperature. It provides feedback information to compensate the microheater's current to maintain the sensor's working temperature constant, regardless of ambient temperature change. Test results showed that, with this approach, significant improvement of stability has been achieved compared to SMO gas sensors without temperature compensation under the same ambient variation. The algorithm is realized through a hardware circuit, whose advantages include real time, large feedback gain, and low cost. [ABSTRACT FROM PUBLISHER]

Magnetic field sensors are needed for high-accuracy position, angle, force, strain, torque, and current flow measurements. Molecular beam epitaxy was used to grow tellurium-doped indium-gallium antimonide thin films. Hall effect sensors made from these films have been studied for their magnetic sensitivity and thermal stability. For a range of alloy composition near In0.8Ga0.2Sb and n-type doping levels near 2×1017 cm-3, high magnetic sensitivity from -40°C to +200°C was found with a resolution of better than ±0.5% over the entire temperature range. [ABSTRACT FROM PUBLISHER]

The Alice time projection chamber (TPC) detector will be operated with a gas mixture of 90% Ne and 10% CO2 at the electric field of 400 V/cm. Recent studies favor a three-component mixture by adding about 5% N2, which will improve the stability of the gas against discharges. These operating parameters lead to a nonsaturated drift velocity for electrons but also impose that all external influences on the drift gas must be reduced to minimum. A problematic influence is the temperature variation, which can lead to local fluctuation in the gas density and therefore directly affects the drift velocity. For the Alice TPC, the aim is to have a temperature stability of 0.1degC over the full drift length (2.5 m). The main heat contribution comes from the readout chambers' front-end electronics and one estimates that a total of 30.2 kW must be removed. In this paper we present the cooling strategies for the TPC and discuss the results of the thermal test setup build for validation [ABSTRACT FROM PUBLISHER]

Printed circuit board (PCB) integrated inductors have been adapted for operation as fluxgate sensors. A ring core is made from an electrodeposited permalloy thin film and is sandwiched between the layers of the PCB. The sensor excitation winding is also integrated into the PCB design. The pick-up coil is wound around the frame of the PCB core. Different types of current excitation waveforms with tuned and nontuned pick-up coils were used. The achieved sensitivities for 60 turns of tuned/nontuned pick-up coil, a sinusoidal waveform excitation current of Irms=300 mA, and an excitation frequency of 150 kHz were 13100/1800 V/T. The achieved sensitivity for pulse excitation (Ipeak-peak=900 mA, Irms=184 mA, duty 20%) was 2100 V/T. Noise power density for pulse excitation was 1.2 nTrms/√Hz@1 Hz, noise rms value from 10 mHz to 10 Hz was 3.3 nT. A perming error of 1 μT was measured for a wide range of excitation currents. [ABSTRACT FROM PUBLISHER]

This paper presents a dynamic pressure calibration of the fiber-optic interferometric sensor based on highly birefringent side-hole fibers. Earlier, we tested other types of fiber-optic sensors based on the same principle for measurements of static and quasi-static pressure. To apply the sensor for measurements of fast pressure changes, the dynamic analysis is crucial due to the occurrence of resonance phenomena and due to the possibility of false pressure readings. We applied a static calibration procedure to initially determine the pressure sensitivity and temperature stability of the sensor. Next, we compared the characteristics of the fiber-optic sensor with the responses of a calibrated piezoelectric dynamic pressure sensor at an operating range of 110 bar with a sampling rate equal to 200 kHz. The characteristics of the fiber-optic sensor are in good agreement with those of the reference piezoelectric sensor for the linear and exponential functions and for the half-sine when the pulse is wider than 400 ms. However, for half-sine pulses narrower than 250 ms, resonance oscillations occur only in the reference sensor. Construction of the fiber-optic sensor reduces the undesirable oscillations, which thereby makes it possible to operate on frequencies higher by about one order than in the case of the piezoelectric sensor. It clearly shows that the highly birefringent fiber-optic sensors can be successfully applied for measurements of rapid pressure changes. [ABSTRACT FROM PUBLISHER]

Surface acoustic wave (SAW) filters for low-frequency (38-65 MHz) applications have been developed using a radio frequency (RF)-magnetron-sputtered ZnO film on fused-quartz substrates. SAW propagation characteristics such as electromechanical coupling coefficient (K2), SAW phase velocity (v), insertion loss, and temperature coefficient of delay (TCD) have been measured. The intergidital transducer (IDT)/ZnO/fused-quartz device structure yields almost zero TCD (1 ppm·°C-1) with 0.316 λ thick ZnO layer (for the device operating at 60 MHz). Alternately, an overlayer of positive TCD material (ZnO itself) has also been deposited on the IDT/ZnO(<0.316 λ)/fused-quartz device at a low substrate temperature to reduce the TCD. A modified layered structure consisting of ZnO/IDT/ZnO/fused quartz yields almost zero TCD (-3 ppm·°C-1) with a 5.3-μm-thick ZnO overlayer and a 8.1-μm-thick (0.183 λ) ZnO bottom layer. Experimentally obtained SAW propagation characteristics have been compared with the theoretical results. [ABSTRACT FROM PUBLISHER]

The 1.27-μm InGaAs:Sb-GaAs-GaAsP vertical cavity surface emitting lasers (VCSELs) were grown by metalorganic chemical vapor deposition and exhibited excellent performance and temperature stability. The threshold current varies from 1.8 to 1.1 mA and the slope efficiency falls less than ∼35% from 0.17 to 0.11 mW/mA as the temperature is raised from room temperature to 75°C. The VCSELs continuously operate up to 105°C with a slope efficiency of 0.023 mW/mA. With a bias current of only 5 mA, the 3-dB modulation frequency response was measured to be 8.36 GHz, which is appropriate for 10-Gb/s operation. The maximal bandwidth is estimated to be 10.7 GHz with modulation current efficiency factor of ∼5.25GHz/(mA)12/. These VCSELs also demonstrate high-speed modulation up to 10 Gb/s from 25°C to 70°C. We also accumulated life test data up to 1000 h at 70°C/10 mA. [ABSTRACT FROM PUBLISHER]

Lithium-ion 18650-cell capacity has increased dramatically in recent years because of the fierce market competition. One of the major lithium-ion cell manufacturers, GP, introduced GP L210, the UL-certified 18650-cell into the market in 2001. The major evaluation results of this product including the cycle life, rate capability from room temperature to -30°C at various rates, high temperature stability, UL overcharge, impact, crush, flaming particle, and 150°C oven test are reported. Test results confirm that GP L210 not only obtains the highest cell capacity in the existing market, but also achieves a high abuse tolerance. [ABSTRACT FROM PUBLISHER]

In this paper, we discuss the conditions under which we can correctly extract a variety of module parameters of single mode bidirectional optoelectronic duplexer and diplexer modules during relatively slow thermal cycling between -40°C and +85°C. The obtained values of parameters such as tracking error, optical crosstalk, and the laser diode characteristic temperature have been compared for bidirectional modules from different manufacturers and the impact on these parameters of different interconnect techniques, like microoptic (Mo), silicon optical bench, and planar lightwave circuit technologies is discussed. It is shown that there is a conflict between small threshold currents and good temperature stability for InGaAsP-based Fabry-Perot laser diodes emitting at 1300 and 1550 nm. Then the results of spatially low coherence reflectometry for the different bidirectional module types are presented. [ABSTRACT FROM PUBLISHER]

The wavelength-sensitive transparent properties of direct-bandgap semiconductor optical diodes (DBSODs) can be utilized for wavelength sensing. A simplified theory is used to describe the operation principles of such wavelength sensing schemes. The principles fan be applied to realize different measures, including sensing with or without pilot tone for single wavelength or multiple wavelengths. The simplified theory can also provide an easy way for estimating the wavelength resolution and accuracy. The wavelength resolution is demonstrated to be better than 0.01 nm by detecting the induced junction voltage for a fixed bias. The resolution is limited by the current resolution of the bias source to 0.03 nm when the wavelength is to be discriminated by transparent current detection. The feasibility and limitation of multiwavelength sensing using a single semiconductor optical amplifier are addressed both theoretically and experimentally. The limiting factors, including the power dependency and temperature stability, of the sensing schemes are also investigated [ABSTRACT FROM PUBLISHER]