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Low Power Consumption Distributed-Feedback Quantum Cascade Lasers Operating in Continuous-Wave Mode above 90°C at λ ～ 7.2 μm
摘要： We report on the design and fabrication of ?? ～ 7.2 ??m distributed feedback quantum cascade lasers for very high temperature cw operation and low electrical power consumption. The cw operation is reported above 90°C. For a 2-mm-long and 10-??m-wide laser coated with high-reflectivity on the rear facet, more than 170 mW of output power is obtained at 20°C with a threshold power consumption of 2.4 W, corresponding to 30 mW with a threshold power consumption of 3.9 W at 90°C. Robust single-mode emission with a side-mode suppression ratio above 25 dB is continuously tunable by the heat sink temperature or injection current.
关键词： high temperature operation,Distributed feedback quantum cascade lasers,low power consumption,continuous-wave mode
更新于2025-09-12 10:27:22
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Dual growth mode of boron nitride nanotubes in high temperature pressure laser ablation
摘要： The morphological analysis of the end of boron nitride nanotubes (BNNTs) using high-resolution transmission electron microscopy (HR-TEM) can provide valuable insight into the growth mechanism in high temperature pressure (HTP) laser ablation where the best quality of BNNT materials can be obtained so far. Two growth modes of BNNT coexisting during the synthesis process have been proposed based on HR-TEM observation and length analysis. One is the root growth mode, in which boron nitride (BN) species formed via the surface interaction between surrounding N2 molecules and boron nanodroplets incorporate into the tubular structure. Another mode called open-end growth mode means the prolongation of tube growth from the exposed BN edge surrounding the surface of boron nanodroplets which is constructed by the heterogeneous nucleation of absorbed BN radicals from the gas plume. The statistical data, the proportions of end structures and the length of BNNTs, could be fitted to two growth modes, and the open-end growth mode is found to be especially effective in producing longer nanotubes with a higher growth rate. The scientific understanding of the growth mechanism is believed to provide the control for optimized production of BNNTs.
关键词： growth mechanism,high temperature pressure laser ablation,open-end growth mode,root growth mode,boron nitride nanotubes,HR-TEM
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Dual-Lasing Channel of a High-Temperature Terahertz Quantum Cascade Laser
摘要： Terahertz (THz) quantum cascade lasers (QCLs) are powerful coherent light sources covering the frequency range from 1.2 to 5.4 THz, but still suffer from operation temperatures below 200 K. Here, we show the results of a barrier height study for a three-well active region based on GaAs/AlxGa1-xAs heterostructure with changing Al concentrations from x = 12% to 24%. Higher barriers reduce the thermal leakage of electrons at elevated temperatures and reduce the coupling of the electron wave functions. The calculated energy difference of these two electronic states (1.75 meV) agrees with the separation of the two regions in the measured frequency spectrum at 3.4 and 3.8 THz (ΔE = 1.65 meV) at low temperature. With this technique we expect to improve the maximum operation temperature and to optimize broadband devices which are necessary for frequency combs and mode-locked devices.
关键词： Quantum Cascade Laser,High-Temperature Operation,Dual-lasing Channel,Terahertz
更新于2025-09-12 10:27:22
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Performance optimization of complicated structural SiC/Si composite ceramics prepared by selective laser sintering
摘要： Combining reaction-bonded (RB) process and selective laser sintering (SLS) method is an e?ective approach to prepare ceramic components with complex shapes. The purpose of this paper is to ?nd e?cient ways to improve the performance of SiC/Si composites prepared by SLS/RB technologies. E?ects of epoxy resin binder on the performance and microstructure of preforms and sintered bodies were studied ?rst. Then, based on the above results, graphite with low reactivity was used as an alternative slow-release carbon source to promote sintering densi?cation process and improve the carbon density of preforms. When the added amount of graphite increased, clusters of nanometer-sized SiC grains formed and the silicon phase transformed into pieces, which reduced the content and dimension of silicon phase. Furthermore, by applying a two-step sintering method, the residual silicon content of SiC/Si composites decreased further and the ?exural strength at high temperatures increased.
关键词： Performance enchantment,High-temperature behavior,Selective laser sintering,Reaction-bonded process
更新于2025-09-12 10:27:22
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Characterization and analysis on micro-hardness and microstructure evolution of brass subjected to laser shock peening
摘要： In view of the temperature distribution of the high-temperature geothermal tunnels, the surrounding rock temperature was divided into four grades (40 (cid:1)C, 60 (cid:1)C, 80 (cid:1)C and 100 (cid:1)C) to simulate the hot-dry environment. Using the standard curing environment as a reference condition, the mechanical properties and pore structure characteristics of concrete for shotcrete use under hot-dry environments at different temperatures were studied by mechanical and mercury intrusion porosimetry (MIP) tests. Fractal dimension of pore structure was calculated through the fractal model based on thermodynamic method. Bivariate correlation analysis was conducted on the curing temperature and the pore structure parameters. The results show that the 40 (cid:1)C hot-dry environment is conducive to enhance the mechanical properties of concrete and optimize its pore structure at the age of 1d. However, the hot-dry environments after 7 days will deteriorate the mechanical properties and pore structure of concrete, and the higher the temperature, the more obvious the deterioration. There is a significant correlation between curing temperature and porosity of capillary pores, median pore diameter, average pore diameter and fractal dimension.
关键词： Pore structure,Surrounding rock temperature,Mechanical property,Fractal dimension,Concrete for shotcrete use,High-temperature geothermal tunnel,Hot-dry environment
更新于2025-09-11 14:15:04
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Tunable self‐powered n‐SrTiO <sub/>3</sub> photodetectors based on varying CuS‐ZnS nanocomposite film (p‐CuZnS, p‐CuS, and n‐ZnS)
摘要： Dense Boron-doped diamond (BDD) composites were fabricated by high pressure and high-temperature sintering (HPHT) at 5 GPa and 1450 °C for 300 s in presence of Al, B and C as sintering additives. Phase compositions, microstructures, and electrochemical performances of sintered specimens were investigated by X-ray di?raction (XRD), scanning electron microscopy (SEM), and electrochemistry. Results suggested that Al3BC3 and Al4C were formed by in-situ reaction between sintering additives and diamond, which can promote densi?cation of BDD. In addition, BDD composites containing 10 wt% sintering additives exhibited the highest electrical resistivity (4.40 × 10?4 Ω m) and hole concentration (4.55 × 1025/m3). The working potential windows of BDD composite electrodes in 0.1 M H2SO4, 0.1 M Na2SO4 and 0.1 M NaOH electrolytes were estimated to 1.9 V, 2.9 V and 2.3 V, respectively. Electron transfer coe?cients of composite electrodes approached 0.5, con?rming good reversibility. Finally, methylene blue was completely degraded by BDD composite electrodes within 120 min using NaCl as supporting electrolyte.
关键词： High-pressure and high-temperature sintering,Boron-doped diamond,Electrochemical performances
更新于2025-09-11 14:15:04
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Ultra-Robust Deep-UV Photovoltaic Detector Based on Graphene/(AlGa) <sub/>2</sub> O <sub/>3</sub> /GaN with High-Performance in Temperature Fluctuations
摘要： A strategy of adopting Ga2O3 alloyed with Al element to reduce the oxygen vacancy defect density and to enhance the interface barrier height of Ga2O3 heterojunction is proposed to fabricate deep-UV photovoltaic detectors with high thermal stability, high photoresponsivity and fast response speed. Here, a graphene/(AlGa)2O3/GaN device with a photoresponsivity of ~20 mA/W, a rise time of ~2 μs and a decay time of ~10 ms is presented at 0 V bias. At the working temperature of 453 K, the device still exhibits a photo-to-dark current ratio (PDCR) of ~1.8×103, which is 1-2 orders of magnitude higher than that of reported high temperature deep-UV film detectors. By comparing the formation energy of oxygen vacancy defects and the interface barrier height of heterojunction at different temperatures in graphene/Ga2O3/GaN and graphene/(AlGa)2O3/GaN systems respectively, the strategy of synthesizing (AlGa)2O3 ternary composite alloy is proved reliable for fabricating high performance deep-UV photovoltaic detectors. The method proposed in this paper can provide reference for the preparation of deep-UV photovoltaic detectors with high photoresponsivity and thermal stability in the future.
关键词： deep-UV,high temperature,photovoltaic,(AlGa)2O3,high photo-to-dark current ratio
更新于2025-09-11 14:15:04
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High-Temperature β-Ga$_2$O$_3$ Schottky Diodes and UVC Photodetectors using RuOx Contacts
摘要： High-temperature β-Ga2O3 Schottky diodes with very low leakage currents, capable of sensitive UVC detection at 350 oC, were fabricated on 201 β-Ga2O3 single crystal substrates using intentionally-oxidized ruthenium (RuOx) Schottky contacts (SCs), with x = ~2.1. These RuOx:β-Ga2O3 SCs were characterized by rectification ratios of more than 1010 at ± 3 V and very low reverse leakage current densities of less than 1 nAcm-2 (~1 pA) at ?3.0 V, that were unchanged from 24 to 350 oC. These very low high-temperature leakage currents were due to their extremely high Schottky barriers of 2.2 eV at 350 oC, that were stable against repeated operation at this temperature. Although not optimized for photodetection, these SCs could detect UVC (λ = 248 nm) radiation at a temperature of 350 oC with a UVC/dark current ratio of ~103. The very high and thermally stable rectifying barriers of these RuOx:β-Ga2O3 SCs makes them strong candidates for use in high temperature β-Ga2O3 rectifying diodes and UVC photodetectors.
关键词： High Temperature Devices,Schottky Contacts,RuO2,Ga2O3,Ruthenium Dioxide,UV Photodetectors
更新于2025-09-11 14:15:04
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Temperature- and Time-Dependent Mechanical Behavior of Post-Treated IN625 Alloy Processed by Laser Powder Bed Fusion
摘要： The microstructure and mechanical properties of IN625 alloy processed by laser powder bed fusion (LPBF) and then subjected to stress relief annealing, high temperature solution treatment, and hot isostatic pressing were studied. Tensile testing to failure was carried out in the 25–871°C temperature range. Creep testing was conducted at 760°C under 0.5–0.9 yield stress conditions. The results of the present study provided valuable insights into the static and creep properties of LPBF IN625 alloy, as compared to a wrought annealed alloy of similar composition. It was shown that at temperatures below 538°C, the mechanical resistance and elongation to failure of the LPBF alloy were similar to those of its wrought counterpart, whereas at higher temperatures, the elongation to failure of the LPBF alloy became significantly lower than that of the wrought alloy. The solution-treated LPBF alloy exhibited significantly improved creep properties at 760°C as compared to the wrought annealed alloy, especially under intermediate and low levels of stress.
关键词： additive manufacturing,nickel-based superalloys,high temperature mechanical properties,creep resistance
更新于2025-09-11 14:15:04
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A study on film hole drilling of IN718 superalloy via laser machining combined with high temperature chemical etching
摘要： A novel method of laser machining combined with high temperature chemical etching (LMHTCE) was proposed. This novel method can take full advantage of both approaches to drill film holes in an IN718 superalloy without a recast layer or a heat affect zone (HAZ). A solution of hydrochloric acid and sodium nitrate, which minimally reacts with IN718 at room temperature but rapidly reacts under high temperatures, was tested and chosen. Holes drilled in air, water, and chemical solutions by a pulsed laser of 1064 nm were studied, and scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were employed to detect the morphology of the holes and the elemental distribution in different zones. The holes processed in the chemical solution had fewer defects compared with those in the other two mediums. The defocusing distance parameter was optimized to minimize the hole diameter and taper. When the defocusing distance was 0 μm in the drilling stage and ? 60 μm in the high temperature chemical etching stage, a hole with a smaller diameter and taper can be obtained.
关键词： High temperature chemical etching,Laser machining,Film holes,IN718
更新于2025-09-11 14:15:04