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High-Sensitivity Temperature Sensor Based on Polarization Maintaining Fiber Sagnac Loop
摘要： A high-sensitivity all-fiber temperature sensor based on a Sagnac interferometer is demonstrated by splicing a section of polarization maintaining fiber (PMF) between two sections of standard single mode fibers (SMFs). In this sensor, the SMF-PMF-SMF structure in the Sagnac loop is bent into a circle to enhance the sensitivity. The length and curvature of the PMF in the loop are investigated and can be optimized to further increase the temperature sensitivity of the sensor. Results show that the radius of the circle has an important effect upon temperature sensitivity due to the bend-induced birefringence variation of the PMF. The SMF-PMF-SMF structure bent into a circle with a radius of 30 mm exhibits a high-sensitivity temperature of 1.73 nm/℃. The sensor is provided with the advantages of easy fabrication, low-insertion loss, and high sensitivity, which may find potential applications in the field of high precision temperature measurement.
关键词： polarization maintaining fiber,Sagnac loop,Optical fiber sensor,temperature sensor
更新于2025-09-09 09:28:46
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Elastic and thermophysical properties of BAs under high pressure and temperature
摘要： The pseudopotential plane-wave approach in the framework of the density functional theory, and the density functional perturbation theory with the generalized gradient approach for the exchange-correlation functional has been used to calculate the structural phase stability, elastic constants and thermodynamic properties of boron-arsenide (BAs) compound. The BAs compound transforms from the zincblende phase to rock-salt structure; the phase transition pressure was found to be 141.2 GPa with a volume contraction of around 8.2 %. The thermodynamic properties under high pressure and temperature up to 125 GPa and 1200 K respectively were also determined, analyzed and discussed in comparison with other data of the literature. The systematic errors in the static energy were corrected using the bpscal EEC method. Our results agree well with those reported in the literature, where for example, our calculated melting temperature (2116 K) deviates from the theoretical one (2132.83 K) with only 0.8 %, and the deviation between our result (1.86) of the Grüneisen parameter and the theoretical one (1.921) is only around 3.2 %.
关键词： Phase transition,Thermodynamic properties,High-pressure,High-temperature,Boron arsenide
更新于2025-09-09 09:28:46
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Investigation on the dynamic characteristics of LIBS for heavy metal Mn in liquid matrix
摘要： Laser-induced breakdown spectroscopy in composition analysis of materials has many advantages over other analytical methods.Based on our Laser Induced Breakdown Spectroscopy (LIBS) survey system of heavy metals in the mixed solution and the optimum experimental parameters, we measured the integrated intensities of partial spectral lines of Mn when the ICCD gate delay time and the sample ?ow rate were ranged from 500ns to 2500ns, 35ml/min to 55ml/min respectively. With increasing the time delay, the electron temperature of the plasma decreases gradually, the electron density decreases ?rstly,then the change amplitude tends to be ?at.As the ?ow rate continue increasing,the electron temperature of plasma increases ?rstly, then the change tends to be ?at, the electron density increase gradually.The element particle density ratio of Mn at ?rst ionization state to ground state and Mn at ?rst ionization state are also obtained respectively. Finally, by comparing the experimental value of spectral line intensity ratio of Mn with the calculated value, the nonexistent conditions of local thermal equilibrium and self-absorption of laser plasma are veri?ed.It provides the suppuration for forward quantitative analysis of the trace heavy metal elements in liquid matrix.
关键词： Liquid matrix,Laser induced breakdown spectroscopy,Elements particle density ratio,Electron temperature,Electron density
更新于2025-09-09 09:28:46
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Effect of PbO–B2O3–BaO–SiO2 glass additive on dielectric properties of Ba0.5Sr0.5TiO3 ceramics for radio-frequency applications
摘要： In this work, the effects of PbO–B2O3–BaO–SiO2 (PBBS) glass addition (in increasing wt%) into Ba0.5Sr0.5TiO3 (BST0) ceramic on sintering, phase, and dielectric properties of BST0 are studied. The Ba0.5Sr0.5TiO3 (BST0) ceramic was synthesized by the conventional solid-state reaction method, and the PbO–B2O3–BaO–SiO2(PBBS) glass was formed by melting and quenching process. The PBBS glass with different weight percentages (3, 5, 8 and 10 wt%)is added to BST0 ceramic (BST3, BST5, BST8, and BST10, respectively) as a sintering aid to reduce the sintering temperature. Addition of glass helps in better sintering at lower temperatures with the presence of liquid phase at the respective sintering temperatures. The results of liquid phase-sintered ceramics are compared with the BST0 ceramic sintered at 1523 K. The BST10 with 10 wt% glass showed the lowest sintering temperature of 1148 K. Rietveld refinement analysis of BST0 ceramic confirmed the formation of single phase with cubic crystal structure. X-ray diffraction patterns of all liquid phase-sintered ceramics showed that the glass has minimal reaction with the BST0 ceramic and does not affect the crystal structure. Dielectric characterization was performed within the temperature range 20–450 K and frequency range 1 kHz to 1MHz. It is revealed that the transition temperature shifted with different weight percentage of glass addition. All the compositions exhibit the paraelectric phase at room temperature. Dielectric properties were also measured in the microwave frequency range 8.5–11 GHz at room temperature.BST10shows the stable and highest dielectric constant (average value of εr = 27) with lowest dielectric loss (tanδ = ~0.121). Fourier transform infrared (FTIR) and Raman spectroscopy confirmed the formation of desired compositions by detecting molecular vibrations and chemical bonding. The synthesized ceramic is a low-cost candidate and can have potential uses in the radio-frequency applications.
关键词： Dielectric properties,Glass,Sintering,Transition Temperature,Calcination
更新于2025-09-09 09:28:46
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Hybrid structure Mach–Zehnder interferometer based on silica and fluorinated polyimide microfibers for temperature or salinity sensing in seawater
摘要： An all-fiber hybrid structure Mach-Zehnder interferometer (MZI) based on silica fiber and fluorinated polyimide microfiber (FPMF) for temperature or salinity sensing in seawater is proposed. Theoretically, transmission characteristic and sensing sensitivity of the MZI are derived for this kind of hybrid structure, and typical interference spectrum is observed around optical communication band. Experimentally, by tracking the shift of interference peaks, temperature and salinity sensing are demonstrated with sensitivities of about 140pm/°C and 64pm/‰, respectively, which are much higher than those of existing fiber Bragg gratings and microfiber knot resonators. In addition, dependences of sensitivity on sensor parameters, such as fiber diameter and fiber lengths, are also investigated. Unlike the other microfiber based sensors that higher sensitivity usually comes from the thinner fiber, sensors demonstrated here show that sensitivities can be tuned by changing the path-length difference of the two arms, which greatly decreases the difficulty in component fabrications. Temperature or salinity sensor demonstrated here show advantages of simple fabrication, low cost, tunable sensitivity and dynamic range, relatively high sensitivity and compatible with standard fiber optics system, which may have potential applications in developing low cost and compact size optical sensors in ocean or other liquid surroundings.
关键词： salinity,temperature,hybrid structure,microfiber,Optical fiber sensor,Mach-Zehnder interferometer
更新于2025-09-09 09:28:46
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U-shaped Microfiber Coupler Coated with Polyvinyl Alcohol Film for Highly Sensitive Humidity Detection
摘要： A probe-type relative humidity (RH) sensor was proposed and developed by combination of a U-shaped microfiber coupler (MFC) and a polyvinyl alcohol coating. Optical MFC is considered as an excellent kind of humidity sensor due to its highly sensitive to the environmental RI changes. By covering one layer of PVA film onto the surface of the waist region of the MFC, the sensitive of the proposed sensor was further increased. Experiment results indicated that the proposed sensor exhibited a good linear relationship between the wavelength and relative humidity over the 15% to 85%RH range and which also exhibited sensitivity are about 318.1 pm/%RH. And temperature experiment results showed that the temperature sensitivity of the proposed sensor is about 13.9 pm/℃ over the 20℃ to 50℃ rang, which indicated that the proposed sensor has the performance of being low temperature sensitive.
关键词： temperature insensitive,humidity detection,PVA film,highly sensitive,U-shaped microfiber coupler
更新于2025-09-09 09:28:46
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Single crystal hybrid perovskite field-effect transistors
摘要： The fields of photovoltaics, photodetection and light emission have seen tremendous activity in recent years with the advent of hybrid organic-inorganic perovskites. Yet, there have been far fewer reports of perovskite-based field-effect transistors. The lateral and interfacial transport requirements of transistors make them particularly vulnerable to surface contamination and defects rife in polycrystalline films and bulk single crystals. Here, we demonstrate a spatially-confined inverse temperature crystallization strategy which synthesizes micrometre-thin single crystals of methylammonium lead halide perovskites MAPbX3 (X = Cl, Br, I) with sub-nanometer surface roughness and very low surface contamination. These benefit the integration of MAPbX3 crystals into ambipolar transistors and yield record, room-temperature field-effect mobility up to 4.7 and 1.5 cm2 V?1 s?1 in p and n channel devices respectively, with 104 to 105 on-off ratio and low turn-on voltages. This work paves the way for integrating hybrid perovskite crystals into printed, flexible and transparent electronics.
关键词： hybrid perovskites,field-effect transistors,single crystals,ambipolar transport,inverse temperature crystallization
更新于2025-09-09 09:28:46
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Charge-stripe crystal phase in an insulating cuprate
摘要： High-temperature (high-Tc) superconductivity in cuprates arises from carrier doping of an antiferromagnetic Mott insulator. This carrier doping leads to the formation of electronic liquid-crystal phases. The insulating charge-stripe crystal phase is predicted to form when a small density of holes is doped into the charge-transfer insulator state, but this phase is yet to be observed experimentally. Here, we use surface annealing to extend the accessible doping range in Bi-based cuprates and realize the lightly doped charge-transfer insulating state of the cuprate Bi2Sr2CaCu2O8+x. In this insulating state with a charge transfer gap on the order of ~1 eV, our spectroscopic imaging scanning tunnelling microscopy measurements provide strong evidence for a unidirectional charge-stripe order with a commensurate 4a0 period along the Cu–O–Cu bond. Notably, this insulating charge-stripe crystal phase develops before the onset of the pseudogap and formation of the Fermi surface. Our work provides fresh insight into the microscopic origin of electronic inhomogeneity in high-Tc cuprates.
关键词： spectroscopic imaging scanning tunnelling microscopy,electronic inhomogeneity,cuprates,charge-stripe crystal phase,high-temperature superconductivity
更新于2025-09-09 09:28:46
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Sulfur doping of M/In <sub/>2</sub> O <sub/>3</sub> (M=Al,W) nanowires with room temperature near infra red emission
摘要： We have investigated the growth of Al doped In2O3 nanowires via the vapor-liquid-solid mechanism at 800?C using Au as a catalyst. We find that the Al is not incorporated into the cubic bixbyite crystal structure of In2O3 but nevertheless was detected in the form of Al2O3. The nanowires had metallic like conductivities and exhibited photoluminescence at 2.3 eV which shifted to 1.5 eV after exposure to H2S above 500?C due to the formation of β-In2S3 and deep donor to acceptor transitions with a lifetime of ≈ 1 μs. The near infra red emission was also observed in W/In2O3 but not in W/SnO2 core-shell nanowires after processing under H2S at 600?C, confirming it is related to β-In2S3. The nanowires remain one dimensional up to 900?C due to the shell which is interesting for the fabrication of high temperature nanowire sensors.
关键词： β-In2S3,M/In2O3 nanowires,Al doped In2O3,room temperature near infra red emission,Sulfur doping
更新于2025-09-09 09:28:46
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Non-equilibrium photoexcited carrier effects in a graphene-based Josephson junction
摘要： We studied the superconducting proximity effect under photoexcitation by illuminating a superconductor/monolayer graphene/superconductor (SGS) Josephson junction with monochromatic light at a wavelength of 1.31 lm. Although the critical current Ic can be controlled by the irradiation power P, its variation cannot be explained by modi?cation of the carrier density, which has been reported for semiconductor-based Josephson junctions. The estimated electron temperature of gra- phene is proportional to Pd, where d ’ 1=3. This relation clearly indicates that photogenerated non- equilibrium carrier dynamics are responsible for the variation of Ic with P. We suggest that the SGS junction can directly mediate interactions between the optical ?eld and the superconducting state.
关键词： electron temperature,photoexcitation,critical current,graphene,Josephson junction,superconducting proximity effect
更新于2025-09-09 09:28:46