Temperature-sensing Characteristics Research Articles

Shell thickness-induced thermal dependence: highly sensitive core-shell CdSe/ZnS/POSS-based temperature probes.

Fluorescence nanothermometry based on quantum dots is a current research hotspot for novel non-contact temperature monitoring, and is of vital significance for the modulation and design of the sensing properties of sensors. Herein, a design strategy to modulate the temperature-sensing characteristics of quantum dots based on the thickness of a shell is proposed. In this study, CdSe/ZnS quantum dot/POSS-based temperature probe films with varying fluorescence characteristics were developed, and the influence of the ZnS shell on temperature sensing was examined by varying the thickness of the ZnS shell. The temperature dependency, linearity, range of applications, and reversibility of quantum dot thin film probes were all considerably regulated by the ZnS shell, according to research on quantum dot/POSS-based films coated with various shell thicknesses. The CdSe/ZnS temperature probe with 4 monolayers (MLs) stood out among the rest due to its strong thermal stability (at least 5 cycles), large usable temperature range (20-80 °C), and excellent temperature sensitivity (R2 > 0.994). The results demonstrated that the temperature sensing performance of quantum dots was the consequence of the combined effect of multiple temperature response properties induced by the thickness of the shell, and the shell control of quantum dots to optimize the temperature sensing performance was an essential approach for the design of temperature probes. This work demonstrates the great potential of the shell in tuning the temperature sensing performance of quantum dots and provides a viable approach for the design of quantum dot temperature probes.

Anti-Counterfeiting Application and Temperature Sensing Characteristics of SrBi4Ti4O15:Yb3+/Er3+ Phosphor Designed by Solid State Method For Dual-Mode Upconversion Luminescence

Anti-Counterfeiting Application and Temperature Sensing Characteristics of SrBi4Ti4O15:Yb3+/Er3+ Phosphor Designed by Solid State Method For Dual-Mode Upconversion Luminescence

Effect of the synthesis route on luminescence dynamics and thermographic properties of Sm3+ doped Ba2Mg(PO4)2 phosphor

The present study investigates the impact of synthesis routes on the structure, optical, and thermographic properties of Ba2Mg(PO4)2:xSm3+ (x = 2 mol.%) phosphor. The two techniques used for the synthesis were combustion synthesis (CS) and solid-state reaction synthesis (SSR). X-ray diffraction analysis confirmed a pure monoclinic phase with space group P21/n in both SSR and CS synthesized samples. The average crystallite size was 41 ± 0.19 nm for SSR and 21 ± 0.02 nm for CS phosphors. Using Fourier transform infrared (FTIR) analysis, the vibrational behavior of both synthesized phosphor samples was analyzed. Both samples displayed a bright orange-red photoluminescence (PL) emission, attributed to the 4G5/2→6H7/2 transition when excited with 403 nm light at room temperature. However, the intensity of PL emission was higher in the CS-prepared sample. The UV-Vis absorption measurements indicated several bands in both samples. The CIE coordinates were calculated for both samples and they corresponded to the shade of orange-red emission of the Sm3+ ions. The study also included an investigation into the temperature-sensing characteristics of the synthesized phosphors, which was performed in the 323–673 K temperature range. The fluorescence intensity ratio (FIR) technique was used to study the non-contact temperature sensing for both samples, and the CS-prepared phosphors exhibited the maximum value of absolute sensitivity (0.00629 K−1) and relative sensitivity (0.26 % K−1) at temperature 673 K. Overall, the results indicate that the CS method provides better results in terms of luminescence and temperature sensing characteristics compared to the SSR method.

Tunable luminescence and noncontact temperature sensing of oxyfluoride glass ceramics containing Na(Y1.5Na0.5)F6:Bi3+/Eu3+ nanocrystals

The oxyfluoride glass ceramics (GCs) containing novel Na(Y1.5Na0.5)F6 (NYNF) nanocrystals: Bi3+/Eu3+ were successfully fabricated. The results of the transmission electron microscope (TEM) showed that NYNF nanocrystals (40–70 nm) are distributed in the glass matrix. Moreover, the luminescence properties of Bi3+/Eu3+ ions-doped NYNF GCs were tested and analyzed. The NYNF GCs exhibit strong emission at blue (412 nm, Bi3+) and red (613 nm, Eu3+) wavelengths when excited with near-ultraviolet (n-UV) light at 288 nm. The emission color can be adjusted from blue (0.1506, 0.0655) to violet (0.3535, 0.1929) by increasing the Eu3+ ion content. Notably, the sample exhibited significant temperature-sensing characteristics as calculated by fluorescence intensity ratio (FIR), with high relative sensitivity (1.731 % K−1) at 548 K. These findings demonstrate the potential application of NYNF: Bi3+/Eu3+ GCs in achieving tunable multicolor luminescence and noncontact temperature measurement.

Temperature Sensing Characteristics of Two Fundamental Solitons in a Glycerin-Filled Microstructured Optical Fiber

In this paper, the temperature sensing characteristics of two fundamental solitons in a glycerin-filled six-hole microstructured optical fiber (MOF) were systematically exploited through experiment and simulation. The six-hole MOF has a large duty cycle, which can increase the space to fill the temperature-sensitive material glycerin for improving the temperature sensing sensitivity. By detecting the center wavelength shift of 3dB bandwidth of two fundamental solitons at 1050 nm, 390 mW, a maximum sensitivity of -0.601 nm/ °C was obtained based on the first fundamental soliton and -0.598 nm/ °C was obtained based on the second. Simulation results combined with the experimental results showed that the higher the average pump power, the higher the temperature sensitivity, and the temperature sensitivity of the first was slightly higher than that of the second. The difference in sensing characteristics between the two fundamental solitons discovered in this study could provide a novel solution to solve the cross-sensitivity of dual-parameter sensing. To the best of our knowledge, this is the first research about utilizing two fundamental solitons for temperature sensing, which broadens the boundary of the nonlinear-based sensors, and has promising prospects in the fields of national defense security, disease monitoring, agriculture production, etc.

Temperature Sensing Characteristics of Improved SNCS Fiber Sensor

Temperature Sensing Characteristics of Improved SNCS Fiber Sensor

Temperature Sensing Characteristics of a Four-Core Sapphire Derived Fiber Based on Supermode Interference

A Mach–Zehnder interferometer (MZI) sensor based on a coupled four-core sapphire-derived fiber (FSDF) for temperature sensing is proposed and demonstrated. The coupled FSDF with a high refractive index (RI) difference between core and cladding can support four LP01-like supermodes (LP01s modes) and eight LP11-like supermodes (LP11s modes). We have fabricated and investigated two sensor samples with a sensing length of 3.1 cm (Sensor I) based on LP01s-LP11s mode interference and with a sensing length of 9.0 cm (Sensor II) based on LP01s-LP01s mode and LP11s-LP11s mode interference. The high-temperature behaviors of both sensors were studied after annealing at temperatures up to 900 °C. The experimental results show that the temperature sensitivity of Sensor I is around 70 pm/°C. For Sensor II, multiple supermode interferences are involved providing different sensitivities. The sensitivity based on the first-order LP01s and second-order LP01s interference is about 136 pm/°C, and the sensitivity based on the first-order LP01s and fourth-order LP01s mode interference is about 36 pm/°C. The sensitivity based on two LP11s mode interference achieves about 64 pm/°C. The experimental results are compared to theoretical simulation. The theoretical simulations give additional information on how the geometry of the coupled multicore fiber affects its temperature properties. Adjusting the core radius and the core pitch is shown to have a considerable influence on the achievable sensitivity and may even change the sign of the sensor sensitivity to temperature. Therefore, designing a specific geometric structure of the coupled fiber is beneficial to optimize the sensing characteristic of this type of sensor.

Single-Mode Input Fiber Combined with Multimode Sensing Fiber Used in Brillouin Optical Time-Domain Reflectometry

Conventional single-mode fiber (SMF) Brillouin optical time-domain reflectometry (BOTDR) suffers from a low signal-to-noise ratio (SNR) and severe sensing reliability due to the influence of the stimulated Brillouin scattering threshold and bend loss. In this study, a simple and low-cost distributed sensing structure, with a single-mode input fiber alignment fusion and a 50 μm diameter graded index multimode sensing fiber, is designed, and the SNR characteristic is investigated. Through theoretical derivation and experimental verification, a higher SNR and excellent bending resistance are realized in BOTDR. The experimentally measured improvements in the SNR of the proposed sensing structure over the SMF at the beginning and end of a 5 km fiber are 2.5 dB and 1.3 dB, respectively. The minimum bending radius of the sensing structure is 2.25 mm, which is much better than that of the SMFs. The bidirectional optical losses between the SMF and the 50 μm graded index multimode fiber are measured by a simple experiment system and are 0.106 dB and 1.35 dB, respectively. The temperature-sensing characteristics of the sensing structure are measured by the self-built frequency-shift local heterodyne BOTDR sensor, and the measured temperature sensitivity and accuracy are 0.946 MHz/℃ and 1 ℃, respectively. The design provides a reference for BOTDR with a high SNR and has great potential for structural safety and health monitoring of infrastructures.

Temperature-dependent luminescence of Bi3+, Eu3+ co-activated La2MgGeO6 phosphor for dual-mode optical thermometry

Using a high-temperature solid-phase method, a series of La2MgGeO6: Bi3+, Eu3+ samples with different doping amounts of Bi3+ and Eu3+ were obtained. The crystal structure, morphology, luminescence characteristics, temperature-varying luminescence spectrum, fluorescence attenuation curve, and energy transfer mechanism of the samples were explored. In La2MgGeO6: Bi3+, Eu3+ phosphors, Bi3+ and Eu3+ ions occupy the La3+ ion position. Under ultraviolet (UV) excitation, the emission spectra of LMGO: Bi3+ and the excitation spectra of LMGO: Eu3+ have significant spectral overlap, indicating that there is energy transfer between Bi3+ and Eu3+. By adjusting the doping amounts of Eu3+, adjustable luminescence can be obtained in the co-doped samples. According to the varying temperature-dependence trends of Bi3+ and Eu3+ ions, fluorescence intensity ratio technology was used to explore the temperature-sensing characteristics of Bi3+ and Eu3+ ions. The maximum absolute sensitivity and relative sensitivity were 0.074%·K−1 and 2.389%·K−1, respectively. In addition, by monitoring the lifetime decay time of Bi3+ with temperature, the maximum temperature sensitivity of the La2MgGeO6: Bi3+ samples was 4.09%·K−1. The above results indicate that La2MgGeO6: Bi3+, Eu3+ samples can be used as potential luminescent materials for temperature detection.

Optical transition properties, energy transfer upconversion luminescence, and temperature-sensing characteristics of Tm3+/Yb3+ Co-doped oxyfluoride tellurite glass

The optical transition properties of Tm3+ in oxyfluoride tellurite glass were determined by the Judd–Ofelt theory. The radiative transition rates, fluorescence branching ratios, and intrinsic lifetime for interesting transitions or level were obtained. The optimum doping concentration of Tm3+ for sample was examined, and the optimal concentration for upconversion luminescence was 0.1% Tm2O3. The main reason for concentration quenching was nonradiative energy transfer through the cross-relaxation mechanism. In addition, two-photon processes for near-infrared 3H4→3H6 emission and three-photon processes for blue 1G4→3H6 emission of Tm3+ were confirmed by analyzing the dependence of upconversion intensities on the 980 nm fiber laser. The temperature-sensing properties of Tm3+ in oxyfluoride tellurite glass were investigated using 3F2,3 → 3H6 (698 nm) and 3H4→3H6 (801 nm) excited at 980 nm, and the 3F2,3 and 3H4 states of Tm3+ were thermally coupled levels.

Comparative Study on Temperature Sensing Characteristics of Dual Mechanisms in Hollow Core Fiber

Comparative Study on Temperature Sensing Characteristics of Dual Mechanisms in Hollow Core Fiber

Effects of Yb3+ Concentration on Up-Conversion Luminescence and Temperature Sensing Characteristics of Tm3+/Yb3+:Y2o3 Phosphor

Effects of Yb3+ Concentration on Up-Conversion Luminescence and Temperature Sensing Characteristics of Tm3+/Yb3+:Y2o3 Phosphor

Bistable characteristics of hybrid composite laminates embedded with bimetallic strips

A novel bistable hybrid composite laminate embedded with bimetallic strips was designed by combining the stable-state characteristics of the bistable laminate with the temperature-sensing characteristics of the bimetallic strip described in this paper. A contactless method that deforms the bimetallic strip through the temperature field, driving the bistable laminate, is proposed. Firstly, an analytical method based on Dano's theory was developed to determine the principal curvature of the laminates, and qualitative and quantitative comparisons between theoretical, experimental, and numerical results were conducted and showed good agreement. Then, the influence of bimetallic strip characteristics such as the thickness, width, and material properties, along with the aspect ratio of the laminates, on the principal curvature were examined. In addition, the reciprocating drive of the laminates was realized by changing the temperature generated by a thermal field, and the effect of the bimetallic strip arrangement was also studied. Compared with the conventional square bistable cross-ply laminates, it was found that the new laminates have different curvatures in two stable states. In particular, they can be easily driven by changing the ambient temperature (contactless drive), without requiring complicated external driving devices. This study provides theoretical support and a new driving method for the design of adaptive and deployable structures.

Temperature Sensing Characteristics of an MKR in a Microfiber Taper Based on Mechanisms of Interference and Resonance with Vernier Effect

In this work, spectral characteristics and temperature sensing characteristics of an in-line microfiber Mach-Zehnder interferometer (MZI) with an embedded microfiber knot resonator (MKR) is investigated. The microfiber MZI with an MKR (MZIKR) has a dual-effect composite spectrum with comb-like spectrum of the MKR loaded on the dominant interference spectrum. Vernier effect is generated by the MKR via superposition of resonant spectra with three resonant modes circulating in the MKR. This is the first time that Vernier effect is generated in a single MKR, which has advantages of easy fabrication and compact structure compared to the traditional resonant structures with Vernier effect such as two cascaded MKRs. Fast Fourier transform (FFT) and FFT filter are used to analyze and extract the different components of the transmission spectrum of the MZIKR. Temperature sensing characteristics of the different components of the polydimethylsiloxane-coated MZIKR are studied, showing that the interference dip of the MZI spectrum and the envelope dip of the MKR Vernier spectrum achieve a high temperature sensitivity of about -1.8 nm/ °C and about -3.5 nm/ °C, respectively. The proposed sensor has the advantages of easy fabrication, robust structure, and high sensitivity in temperature measurement. The MZIKR with dual-effect composite spectrum may have potential in two-parameter measurement and narrow-band filtering.

Fabrication and Temperature Sensing Characteristics of Dense Apodized Fiber Bragg Grating Array

Fabrication and Temperature Sensing Characteristics of Dense Apodized Fiber Bragg Grating Array

Strain- and Temperature-Sensing Characteristics of Fiber Ring Laser Sensor With Cascaded Fabry–Perot Interferometer and FBG

The strain- and temperature-sensing characteristics of fiber ring laser (FRL) sensors are studied comprehensively. The reflected sensing head, made up of spheroidal Fabry–Perot interferometer (FPI) concatenated with fiber Bragg grating (FBG), is inserted in the cavity of FRL acting as the laser intensity modulator and wavelength selector. The laser intensity is sensitive to temperature change while insensitive to strain, making the dual-parameter demodulation realizable without multivariate matrix by detecting the laser wavelength shift and the laser intensity variation, for the first time in our best knowledge. The comparable sensitivities of 1 pm/ $\mu \varepsilon $ and 24.9 pm/°C are detected in experiment for strain and temperature, respectively, with low detection limit (DL) of 0.87 $\mu \varepsilon $ and 0.035 °C, high $Q$ factor of 1140 and 7.07 $\times \,\,10^{5}$ . The high intensity and narrow linewidth of the sensor make it potentially great for application in long-distance sensing systems.

Temperature-sensing characteristics of NaGd(MoO4)2: Sm3+, Tb3+ phosphors

In this study, Sm3+/Tb3+-co-doped NaGd(MoO4)2 phosphors were prepared via the hydrothermal method, with sodium citrate used as a chelator. X-ray diffraction confirmed the structure of the samples, and the test outcomes showed that the phosphors exhibited a body-centered tetragonal structure. Field-emission scanning electron microscopy results showed that the specimen morphology changed with the change in the Cit3−/Re3+ molar ratio. Moreover, the measured temperature-dependent emission spectra showed that Sm3+ and Tb3+ had different quenching trends; thus, the fluorescence intensity ratio can be used to represent temperature. In addition, the outcome of this experiment revealed that the temperature-sensing sensitivity of the phosphors gradually increased with the increasing Cit3−/Re3+ ratio, and the highest sensitivity value was 0.346 K−1 (at 503 K, Cit3−/Re3+ = 2). When the temperature was 298–369 K, the temperature-sensing relative sensitivity increased with increasing Cit3−/Re3+, but in the range 374–503 K, the relative sensitivity decreased with increasing Cit3−/Re3+. The highest relative sensitivity value of the sample was 2.7% K−1 (404 K, Cit3−/Re3+ = 0). Additionally, the Commission International del’Eclairage chromaticity coordinates displayed that the luminous colors of Sm3+/Tb3+-co-doped specimens continuously changed from green to red as the temperature changed.

Temperature-sensing characteristics of polarization-maintaining fiber Bragg grating inscribed directly by 800-nm femtosecond laser pulses

Abstract A temperature-sensing system based on a polarization-maintaining fiber Bragg grating (PM-FBG) with dual-wavelength peaks was proposed and demonstrated experimentally. First-order bow-tie- and panda-type PM-FBGs with 3-mm gratings were inscribed by a 800-nm femtosecond laser by the point-by-point method, in which the laser was focused onto the fiber core through the fiber coating and cladding. The FBG arrays were directly fabricated by the femtosecond laser writing technique. The PM-FBGs with dual-wavelength reflection-spectrum peaks were scanned by a cost-effective interrogator system using modulated-grating Y-branch (MG-Y) tunable laser to sample the wavelength center position. In the temperature-sensing experiment, the sensitivity of the bow-tie-type PM-FBG exceeded 14 pm/°C within the 30–90 ℃ range. The proposed PM-FBGs and its interrogation system can be widely used in the field of fiber sensing and fiber laser.

Temperature Sensing Characteristics and Long Term Stability of Power LEDs Used for Voltage vs. Junction Temperature Measurements and Related Procedure

A detailed study about the direct measurement of junction temperature Ti of off-the-shelf power light emitting diodes (LED) is presented. The linear dependence on temperature of the voltage drop across the device terminals at a constant current is in particular exploited and fully characterized, in the temperature range from T = 35 °C to 135 °C, with tests repeated at one thousand different probe currents. The accurate experimental data, obtained on several LED samples bearing two different part numbers, are reported, showing that they exhibit a high degree of linearity in wide current ranges, a circumstance that allows for a fast and reliable calibration as sensors. The measurement error is also fully characterized in terms of repeatability and stability over time, with measurements repeated after 600, 900, 1200 and 1800 hours of applied electro-thermal stress, demonstrating that the relevant sensor parameters stabilize after a few hundred hours of operation. A full set of parameters is provided for the two device models, allowing the direct use of each LED for the self-monitoring of the junction temperature and ensure compliance with their safe operating area over time. Moreover, a procedure and a simple circuit for the real time measurement of Ti, while the LED is on, are presented. The procedure does not require a stable current source, and relies instead on the application of a sub-threshold current ramp for such a short time that the change in the output light is not perceived by human eyes.

Relative Humidity and Temperature Sensing Characteristics of an Optical Fiber Probe Based on Hollow-Core Fiber and Calcium Alginate Hydrogel Film

Hydrogel is a kind of functional cross-linked polymer material with 3-D network structure. When hydrogel is exposed to water environment, a mass of hydrophobic groups and hydrophilic residues existing in the cross linked netlike nano-structure is willing to combine with water molecules and expand, respectively. In this paper, a novel optical fiber probe based on hollow-core fiber and calcium alginate (CaAlg) hydrogel film is proposed and experimentally demonstrated. The experimental results of relative humidity (RH) and temperature sensing characteristics show that the proposed probe has a binomial response to RH in the range of 20%~90% RH and a linear response to temperature with the sensitivity of 121pm/°C. CaAlg is considered as an effective and potential as the humidity-sensitive material to optical fiber RH sensors.