Optical Temperature Research Articles

Study on a Highly Thermostable Dy3+-Activated Borophosphate Phosphor.

Constructing a phosphor with multifunctional applications is an imperative challenge. Especially, highly thermostable luminescence of phosphor is indispensable for stable white-light-emitting diodes (LEDs). Nevertheless, good thermal quenching resistance behavior is unfavorable for a fluorescence intensity ratio (FIR)-based optical temperature sensor. Herein, a highly thermostable Ba3(ZnB5O10)PO4 (BZBP)-based phosphor is successfully achieved via replacing Ba2+ with Dy3+, demonstrating simultaneously promising lighting and thermometry utilizations. Under the excitation of 350 nm, the title phosphor only loses 12% of the initial intensity when the temperature is up to 473 K, ensuring sufficient luminescence thermostability for white-LED lighting. The white-LED device fabricated using the title phosphor emits high-quality white light with a high color rendering index (Ra = 93) and low correlated color temperature (CCT = 3996 K). Meanwhile, the yellow and blue emission intensities demonstrate a downtrend difference with rising temperature. Temperature sensing properties are assessed through FIR technology. The maximal relative sensitivity reaches as high as 0.0379 K-1 at 298 K. These results reveal that the title phosphor has a great potential for indoor lighting and thermometry applications.

Tunable and highly sensitive fluorescent thermometers from La2CaZrO6:Cr3+ with a time-resolved technology.

Non-contact optical temperature measurement can effectively avoid the disadvantages of traditional contact thermometry and thus, become a hot research topic. Herein, a fluorescence intensity ratio (FIR) thermometry using a time-resolved technique based on La2CaZrO6:Cr3+ (LCZO) is proposed, with a maximum relative sensitivity (Sr - FIR) of 2.56% K-1 at 473 K and a minimum temperature resolution of 0.099 K. Moreover, the relative sensitivity and temperature resolution can be effectively controlled by adjusting the width of the time gate based on the time-resolved technique. Our work provides, to our knowledge, new viewpoints into the development of novel optical thermometers with adjustable relative sensitivity and temperature resolution on an as-needed basis.

High-performance of optical thermometry based on the non-thermally coupled levels in YVO4: Yb3+/Er3+/Tm3+ nanocrystals

Hydrothermally fabricated nanocrystals YVO4: Yb3+/Er3+/Tm3+ were investigated for up-conversion (UC) luminescence and optical temperature sensing performance. Upon 980 nm excitation, the luminescence intensity firstly increases and then decreases with raising Yb3+ doping content and reaches the maximum at 15 mol%. Considering the strong UC emission, the temperature sensing behavior was investigated based on the fluorescence intensity ratio (FIR) technique in temperature range of 293–573 K. The study was focused on the non-thermally coupled levels (NTCLs) including transitions 3F2,3 → 3H6 and 1G4→3H6 of Tm3+, transitions from the 4S3/2, stark sublevel 4S3/2(2), and 4F9/2 to the ground state 4I15/2 of Er3+ owing to their various temperature-dependent behaviors. Through using the stark sublevel 4S3/2(2) of Er3+, the maximum absolute sensitivity (SA) of 0.0563 K-1, relative sensitivity (SR) of 2.334 %K−1 and the minimum temperature resolution of 0.0058 K was achieved with good repeatability. The experimental results indicate that the as-obtained YVO4: 15%Yb3+/1%Er3+/1%Tm3+ nanocrystals can be potential candidates for nano-dimensional optical thermometry applications.

Er3+/Yb3+/Ho3+ tri-doped no-core fiber temperature sensor based on fluorescence intensity ratio technology: towards high stability and accurate measurements.

In this paper, the green upconversion (UC) fluorescence emission from E r 3+/Y b 3+/H o 3+ tri-doped tellurite glass is investigated for temperature sensing. The doping of H o 3+ ions not only enhances the chance of energy level transition but also avoids the influence of the thermal effect caused by the proximity of 2 H 11/2 and 4 S 3/2 energy levels. The luminescence characteristics at different Y b 3+ and H o 3+ ion concentration doping molar ratios were investigated, and the strongest luminescence characteristics were exhibited when the Y b 3+ ion concentration was at 5mol% and H o 3+ at 0.2mol%. Based on this, a tri-doped T e O 2-Z n O-B i 2 O 3 (TZB) no-core fiber was fabricated and connected with multimode fibers (MMFs) to form a temperature sensor. The temperature sensing performance of the tri-doped TZB temperature sensor was evaluated in detail over the temperature range of 255-365K. The repeatability and stability of the temperature sensor was experimentally verified. The E r 3+/Y b 3+/H o 3+ tri-doped sensor can be used for noninvasive optical temperature sensing in the fields of environmental monitoring, biological sensing, and industrial process temperature control, etc.

Novel Nanocomposites for Luminescent Thermometry with Two Different Modalities.

In this work, we successfully integrated fluorescent nanodiamonds (FNDs) and lanthanide ion-doped upconversion nanoparticles (UCNPs) in a nanocomposite structure for simultaneous optical temperature sensing. The effective integration of FND and UCNP shells was confirmed by employing high-resolution TEM imaging, X-ray diffraction, and dual-excitation optical spectroscopy. Furthermore, the synthesized ND@UCNP nanocomposites were tested by making simultaneous optical temperature measurements, and the detected temperatures showed excellent agreement within their sensitivity limit. The simultaneous measurement of temperature using two different modalities having different sensing physics but with the same composite nanoparticles inside is expected to greatly improve the confidence of nanoscale temperature measurements. This should resolve some of the controversy surrounding nanoscale temperature measurements in biological applications.

Upconversion luminescence and temperature sensing performance of Zn2+-doped Ba2GdAlO5: Yb3+, Er3+ phosphors

Although upconversion luminescence (UCL) materials have attracted considerable attention in biomedical, lighting, anti-counterfeiting, and solar cells due to their excellent fluorescence properties, reports of the dibarium gadolinium aluminum oxide (Ba2GdAlO5) are scarce. Herein, we synthesized the single-phase Ba2GdAlO5 material with non-stoichiometric Ba2Gd1.06Al0.94O5 (denoted as BGAO, hereafter). The X-ray Rietveld refinement reveals that the substitution of Gd for Al accounts for the non-stoichiometry. Notably, the UCL properties of BGAO are realized by doping with Yb3+ and Er3+ ion pair, and it can be further enhanced significantly by co-doping with appropriate Zn2+ ions. The SEM images show that the particle size increases as the concentration of Zn2+ ions increases. The X-ray Rietveld refinement results of the Zn-doped BGAO: 0.1 Yb3+, 0.03Er3+ phosphor indicate the substitution of Zn2+ for Ba2+ and Al3+ ions simultaneously. Grain growth and lattice distortion account for the improvement of UCL properties after Zn2+ ions doping. In addition, the temperature sensing performance of the Zn2+-doped sample has been researched based on the fluorescence intensity ratio (FIR) technique, and the maximum absolute and relative sensitivities (SA-max and SR-max) are obtained to be 4.8 × 10−3 K−1 at 498 K and 1.1% K−1 at 298 K, respectively. This work provides a candidate with high UCL intensity for potential applications in optical temperature sensors.

Static and Dynamic Performance of z-LiNbO3 Optical Temperature Sensor

Static and Dynamic Performance of z-LiNbO₃ Optical Temperature Sensor

A three-mode temperature sensing based on UC luminescence of Er:PbF2 crystal

Optical temperature sensor, especially the temperature sensor made based on fluorescence intensity ratio (FIR) technology, have numerous applications in temperature detection. However, most of these sensing materials are phosphors, which still face challenges in maintaining their chemical stability. In contrast, crystal materials exhibit superior thermal stability and fluorescence stability. The temperature sensing characteristics of Er: PbF2 single crystal material were studied by the three modes temperature dependence curve. Excellent relative sensitivity and absolute sensitivity were obtained on FIR between two non-thermally coupled energy levels (non-TCEL: I(4F9/2)/I(4S3/2)) and two thermally coupled energy levels (TCEL: I(2H11/2)/I(4S3/2), and I(4S3/2)/I(4S3/2)) of Er3+ ions when excited by a 980 nm LD. Futhermore, with the increase of temperature, the luminescence emission color of the Er: PbF2 single crystal varied from green to yellow-orange. These discoveries suggest that the Er: PbF2 single crystal could serve as an excellent sensing medium for optical temperature sensors.

Space–Charge‐Limited Photocurrent as a Possible Cause for Low Power Conversion Efficiency in GaInN/GaN‐Based Optoelectronic Semiconductors

This study attempts to understand the cause of low power conversion efficiency (PCE) in III‐nitride optoelectronic semiconductors under optical operation. For this purpose, a GaInN/GaN heterojunction semiconductor is fabricated, and the photoexcited current–voltage (PEJV) curves are carefully measured depending on the optical excitation power and temperature. The results show unexpected excitation power‐ and temperature‐dependent behaviors, that is, the PCE decreases with increasing excitation power and increases with increasing temperature. To understand this, the space–charge‐limited photocurrent (JPh,SCL) theory (also referred to as Goodman and Rose theory) is employed, where the accumulated charge carriers in the active layer play a significant role. The conduction of JPh,SCL is ascertained by analyzing the PEJV curves. The conduction of JPh,SCL is investigated as a possible cause of the low PCE, revealing that the conduction of JPh,SCL could limit the high‐power operation of the device.

Thermometric properties of SrMoO4:Tb3+ phosphor based on redshift of charge transfer band edge

In this study, SrMoO4:Tb3+ phosphors were successfully synthesized for a single-band ratiometric (SBR) thermometry utilizing the redshift of CTB. The SrMoO4:Tb3+ phosphors have a tetragonal system owing to I41/a space group and irregular microparticles possessing a mean size of 20 μm. The incorporation of Tb3+ ions into the SrMoO4 matrix lattice leads to a reduction in the bandgap energy owing to occurrence of defects level in gap-band. Thermal quenching concentration of Tb3+ is 1%, due to the dipole-dipole interaction between Tb3+ and Tb3+ ions. This study observed an interesting redshift in the edge of the CTB with increasing temperature, which can be explained using the configurational coordinate diagram. This phenomenon can be utilized to construct this SBR temperature measurement strategy by selecting appropriate excitation peaks or bands with different thermal responses. The study also demonstrated that SrMoO4: 1%Tb3+ has higher Sa value of 13.31 × 10−2 K−1 @573 K and Sr value of 3.54 K-1@298 K in optical thermometry, making it a suitable candidate for optical temperature measurement.

Double-perovskite LaBaZnTa1-xMnxO6 phosphors for wide-range optical thermometer and high-quality WLED devices

Due to the huge food demand of the population, the luminescent materials with excellent performance applied for indoor plant cultivation have been extensively studied. In this work, a series of Mn4+-doped LaBaZnTaO6 phosphors in were synthesized and its luminescence mechanism has been researched in detail. Due to their broad absorption band, they could be effectively excited by the NUV to blue LED chip. Importantly, suitable emission in the red region overlapped with the absorption of plant pigments making it possible to be used in indoor plant cultivation. On the other hand, high-sensitivity non-contact optical temperature sensor is the focus of current research, so the optical thermometer-based lifetime model also was designed and investigated in this work. Interestingly, the maximum relative sensitivity was 1.38 %K−1@473 K, suggesting a good development potential of the sample in optical thermometry. Finally, the warm WLED device was fabricated and achieved a superior CRI value of 90.95 and a good CCT of 3582 K. All the obtained results suggest that it could become a promising red component to be applied in optical thermometer and lighting sources.

Ca2LaTaO6:Bi3+/Mn4+ Phosphors with High Brightness Far-Red Emitting and Luminescence Enhancement for Plant Growth LED Lights and Temperature Sensor.

Herein, Bi3+/Mn4+ doped Ca2LaTaO6 phosphors with a double-perovskite structure were successfully synthesized with solid-state reaction at high temperature. The photoluminescence (PL) performances were investigated in detail. The blue radiation (∼465 nm) from the Bi3+ ion and the red radiation (∼686 nm) originating from the Mn4+ ion were obtained under 313 nm excitation. Especially, the pathway of energy transfer (Bi3+ → Mn4+) contributes to enhance the red emission intensity (Mn4+: ∼686 nm) in Ca2LaTaO6:Bi3+/Mn4+ system. The PL mechanism of Ca2LaTaO6:Bi3+/Mn4+ was analyzed through luminescence lifetimes and PL spectra. Moreover, the emitting bands of Ca2LaTaO6:Bi3+/Mn4+ were primarily matched with the absorbing bands of carotenoids and phytochrome PFR on behalf of plant growth, so the phosphors were suitable for the design of a plant growth light under near-ultraviolet to blue excitation. At last, the optical temperature dependent performances of the Ca2LaTaO6:Bi3+/Mn4+ were analyzed with luminescence intensity ratio technology. The sample has presented excellent temperature measuring relative sensitivity (SR = 2.106% K-1). The results illustrated that the Ca2LaTaO6:Bi3+/Mn4+ phosphor also can be used to develop an optical temperature sensor.

Cross-physical field prediction method for smoke field distribution in commercial building fire based on distributed optical fiber sensor

In modern commercial building spaces, the smoke generated during indoor fires poses a substantial safety threat to individuals attempting to evacuate. This study leveraged a distributed optical fiber temperature sensing system as the technological foundation. A series of commercial building space models were constructed by employing fire dynamics simulations, and a comprehensive database of simulated fire field information was established. The study built upon this database and proposed a method to establish influence pathways from existing temperature field detection data to three fire risk assessment parameters: carbon dioxide, oxygen, and visibility. The study utilized various machine learning algorithms and focused on selecting and constructing cross-physical field prediction models that optimized the performance of fire risk assessment parameters at the fire key plane. The findings demonstrated that the Multilayer Perceptron (MLP) algorithm model yielded the most accurate fit for carbon dioxide volume fraction, with a Mean Absolute Percentage Error (MAPE) of 3.80% between the model predictions and actual values. The Artificial Neural Network (ANN) algorithm showed superior fitting effects for oxygen volume fraction and visibility, with MAPEs of 1.37% and 3.10%, respectively. Furthermore, the study validated the generalizability of these optimal models by altering spatial scales, revealing robust performance. This study utilized a single optical fiber sensor to achieve dynamic prediction across different physical fields during fire incidents, expanding the application scope of optical fiber sensors in monitoring gas and visibility fields in commercial building fires. This not only enhanced the level of fire monitoring but also effectively reduce equipment costs. It provided effective data support for planning evacuation routes for individuals and rescue arrangements for firefighters, further ensuring personnel safety.

Creating Deep Traps in Yttrium Aluminum Garnet for Long‐Term Optical Storage and Afterglow‐Intensity‐Ratio‐Based Temperature Sensing

AbstractDeep traps are needed for electron‐trapping‐based long‐term optical storage due to its resistance to thermal erasure. Current electron trapping materials have the erasing temperatures hardly beyond 600 K, limiting its storage time. Herein, an electron trapping material containing deep traps is achieved by co‐doping Tb and Eu in Y3Al5O12 via solid‐state reaction in reducing atmosphere. After 254 nm UV charging, strong thermoluminescence of Tb3+ with the glow curve peaking at 600, 693, and 765 K is observed. The comparative studies of the as‐made and the air‐annealed samples suggest that these new traps are related to the complex defects containing oxygen vacancy with adjacent Eu2+ and the charging process is the photoionization of Tb3+ with subsequent electron trapping. The 693 and 765 K thermoluminescence glow peaks in the charged sample show almost no decrease during 108 h storage in dark at room temperature. Images write‐in and read‐out via 808 nm laser stimulation are realized. Furthermore, the present phosphor also exhibits temperature‐sensitive afterglow spectra in the range of 553–803 K with the sensing span of 250 K wider than other afterglow thermometers. These findings indicate the great application potentials of Y3Al5O12:Tb,Eu phosphor in long‐term optical storage and temperature sensing.

Brief Review of Recent Developments in Fiber Lasers

This review covers the recent achievements in high-power rare earth (RE)-doped fiber lasers, Raman fiber lasers, and Brillouin fiber lasers. RE-doped fiber lasers have many applications such as laser cutting, laser welding, laser cleaning, and laser precision processing. They operate in several wavelength ranges including 1050–1120 nm (ytterbium-doped fiber lasers), 1530–1590 nm (erbium- and erbium–ytterbium-doped fiber lasers), and 1900–2100 nm (thulium- and holmium-doped fiber lasers). White spaces in the wavelength spectrum, where no RE-doped fiber lasers are available, can be covered by Raman lasers. The heat power generated inside the laser active medium due to the quantum defect degrades the performance of the laser causing, for example, transverse-mode instability and thermal lensing. It can even cause catastrophic fiber damage. Different approaches permitting the mitigation of the heat generation process are considered in this review. Brillouin fiber lasers, especially multiwavelength Brillouin fiber lasers, have several important applications including optical communication, microwave generation, and temperature sensing. Recent progress in Brillouin fiber lasers is considered in this review.

Comparative study on fluorescence intensity ratio and chromatic coordinate temperature measurement using CsPbBr3-Eu3+ co-doped glass

We have fabricated CsPbBr3-Eu3+ co-doped glass for optical temperature measurement. Photoluminescence (PL) spectra, PL excitation (PLE) spectra and PL decay have been measured. The CsPbBr3 and Eu3+ show distinguishable PL spectra and different temperature dependences. Fluorescence intensity ratio (FIR) and chromatic coordinate temperature measurements are investigated. Absolute sensitivity (Sa), relative sensitivity (Sr) and temperature measurement accuracy (UT) are analyzed. For the FIR method, the Sa and Sr are better in comparison with other temperature sensing materials. The chromatic coordinate is calculated by using PL spectra. Comparing with FIR method, the chromatic coordinate method has smaller Sa and Sr, but better UT due to small uncertainty Ur(x). In addition, the chromatic coordinate method has linear temperature dependence, good compatibility and universality. Both FIR mode and chromatic coordinate mode have excellent temperature cycle characteristics..

Fabry-Perot parallel type high sensitivity fiber optic temperature sensor based on vernier effect beyond free spectral range measurement

Accurate detection of temperature is crucial in industry, agriculture, the military, etc. In our paper, using the vernier effect of fiber optic interference, we demonstrate a temperature sensoru, in parallel with a grating, to improve the sensitivity of the probe while expanding the measurement range. The probe consists of a combination of a temperature-sensitive polymer Fabry-Perot interferometer (SFPI) and a temperature-insensitive 3D printed reference Fabry-Perot interferometer (RFPI). The innovative combination of femtosecond-induced two-photon polymerization provides a reference cavity with determinable cavity length for vernier effects. Innovative use of fiber Bragg grating (FBG) for vernier effect to determine the temperature interval and extend the range. This experiment concluded that the average sensitivity of the parallel probe reached −22.52 nm/°C in the temperature detection interval of 31°C to 37°C, a 16.8-fold increase in sensitivity, based on which the temperature outside the six free spectral ranges (FSR) can be measured in the interval of 31°C to 51°C using the FBG.

Novel GdAlGe2O7:Bi3+,Eu3+ phosphors with anti-thermal quenching properties for high sensitivity optical temperature measurement

The thermometry technique based on fluorescence intensity ratio has attracted much attention for its advantages of fast response, high accuracy, and non-contact. Here, we report a series of novel GdAlGe2O7:Bi3+,Eu3+ phosphors with anti-thermal quenching properties for high sensitivity optical temperature measurement. By constructing the energy transfer between Bi3+ and Eu3+ ions, the GdAlGe2O7:Bi3+,Eu3+ exhibits a rare anti-thermal quenching performance upon 285 nm excitation due to the redshift of the charge transfer band. Therefore, we designed ratiometric optical thermometers with high sensitivity based on the intense thermal quenching behavior of the Bi3+ ions and the anti-thermal quenching property of the Eu3+ ions with a relative sensitivity of 1.06% K−1 at 483 K and an absolute sensitivity of up to 0.0447 K−1 at 573 K. Our results not only reveal the optical behaviors of the Bi3+ and Eu3+ ions in GdAlGe2O7:Bi3+,Eu3+, but also propose that the synthesized phosphors have significant potential applications in the field of optical temperature measurement.

Novel orange-red emitting phosphor Y2MgTiO6:Sm3+ luminescence properties and optical thermometry

The Sm3+-doped Y2MgTiO6 phosphor was successfully synthesized by high-temperature solid-phase method. X-ray diffraction, photoelectron spectroscopy and scanning electron microscopy characterized the phase, electronic structure and morphology. Meanwhile, the luminescence properties were analyzed, and the results showed that the Y2MgTiO6:Sm3+ phosphors emit vibrant orange light when excited at 407 nm, with emission peaks at 565 nm, 603 nm, and 649 nm. The luminescence efficiency of the sample reaches 79.71% of the initial intensity at 423 K. The temperature sensing properties of Y2MgTiO6:Sm3+ phosphors were investigated between different wavelength bands based on the fluorescence intensity ratio (FIR) technique, where FIR (I565/I649) had the maximum relative sensitivity of 0.26% K−1 at 298K. The quantum yield of the sample was 59.88%, with calculated Correlated Color Temperature of 1646 K. The research results suggest that Y2MgTiO6:Sm3+ phosphors have potential applications in optical temperature sensing and w-LEDs devices.

Ni-doped ZnO nanoparticles derived by the sol–gel method: structural, optical, and magnetic characteristics

A simple sol–gel route was used for preparation of Ni doped ZnO nanoparticles (Ni:ZnO) with 0, 3, 5, 7 and 9 wt% of Ni to Zn precursor salts. Structural, optical and room temperature magnetic properties were studied. The prevailing structural arrangement that observed in all the examined samples is the wurtzite structure of ZnO. Nevertheless. The orderly development of NiO rock-salt phase on at the surfaces of ZnO nanoparticles upon Ni doping is confirmed by Rietveld refinements. The ZnO wurtzite structure is dominant in all the samples as confirmed by both XRD and Raman results. The average crystallite size showed almost no change upon Ni doping. RTFM behavior is being exhibited for all Ni:ZnO nanoparticles that is demonstrating using of ZnO as the host structure allowed for the efficient formation of DMS. The Near-infrared solar reflectance (RNIR) and the visible solar reflectance (RVis) values reduced with increasing of the Ni content as a result of the rising in density of trap states upon Ni doping of the samples. Kubelka-Munk method was used to determine the energy band gap (Eg) and band Urbach energy (EU) tails from diffused reflectance (DRS) results. The obtained energy gap values were very close in all studied samples with an average value of energy gap is 3.164 eV. The EU values raise from 123 to 173 meV upon increasing of Ni content in the samples in agreement with lower values of RNIR and RVis and their effect on optical performance of the investigated samples in applications.