Optical Temperature Research Articles

Magnetic-field-assisted optical fiber quantum temperature sensor with enhanced sensitivity.

In recent years, utilizing nitrogen-vacancy color centers in diamond for temperature sensing has drawn great attention. However, increasing the sensitivity has encountered challenges due to the intrinsic temperature-dependent energy level shift, i.e., temperature responsivity, being limited to -74 kHz/K. In this Letter, we take advantage of the magnetic field to regulate the energy level to enhance temperature sensitivity. The sensor is formed by adhering a micron-sized diamond on the end face of an optical fiber, and a small magnet is mounted at a certain distance with the diamond exploiting a cured polydimethylsiloxane block as the bridge. The temperature change leads to the variation of the distance between the diamond and the magnet, thus affecting the magnetic strength felt by the diamond. This finally contributes an additional temperature-induced energy level shift, giving rise to an enhanced sensitivity. Experimental results demonstrated the proposed scheme and achieved a 4.2-fold improvement in the temperature responsivity and a 2.1-fold enhancement in sensitivity. Moreover, the diamond and the fiber-optic integrated structure improve the portability of the sensor.

High temperature fluorescence and multi-mode anti-counterfeiting material based on Eu doping

Due to the influence of the thermal quenching effect, the luminescence intensity of luminescent materials sharply decreases in high-temperature regions, strongly affecting their application in optical anti-counterfeiting and optical temperature supervision. In this study, we report a multi-mode anti-counterfeiting phosphor doped with Eu3+ that exhibits fluorescence thermoluminescence enhancement. This phosphor can trap electrons and release them as luminescence under external stimulation (the light and heat). The compensatory luminescence at high temperatures is the reason for the unique fluorescence thermoluminescence enhancement characteristics of this phosphor. Therefore, the sensitivity and differential response of this phosphor to light and heat can be used to monitor anti-counterfeiting patterns or temperature. This work provides an example for the future application of optical anti-counterfeiting and temperature monitoring.

A Rail-to-Rail Operational Amplifier for Transimpedance Optoelectronic Conversion

The transimpedance conversion circuit is an important part of the fluorescent optical fiber temperature sensor, which is used for rare earth fluorescence detection. Transimpedance conversion circuits can benefit from the wide input range, high gain, low input offset voltage, and high common-mode rejection ratio of rail-to-rail operational amplifiers. In this paper, a constant transconductance rail-to-rail operational amplifier is designed and implemented based on the 0.18 μm CMOS process. According to the simulation results, the transconductance change rate of the operational amplifier is 4.8%, and its gain is 140 dB. The input offset voltage of this operational amplifier is 0.41 μV. Both the power supply rejection ratio and the common-mode rejection ratio have values above 140 dB, with the common-mode rejection ratio reaching as high as 165.4 dB. The transimpedance conversion circuit consists of the operational amplifier designed in this paper. The test results show that the operational amplifier has a certain application value in the transimpedance amplification circuit.

Highly Sensitive Optical Fiber Temperature Sensor Based on Microwave Photonic Filter With Enhanced Vernier Effect

Highly Sensitive Optical Fiber Temperature Sensor Based on Microwave Photonic Filter With Enhanced Vernier Effect

Multifactor roadmap for designing low‐power‐consumed micro thermoelectric thermostats in a closed‐loop integrated 5G optical module

AbstractAs the core components of fifth‐generation (5G) communication technology, optical modules should be consistently miniaturized in size while improving their level of integration. This inevitably leads to a dramatic spike in power consumption and a consequent increase in heat flow density when operating in a confined space. To ensure a successful start‐up and operation of 5G optical modules, active cooling and precise temperature control via the Peltier effect in confined space is essential yet challenging. In this work, p‐type Bi0.5Sb1.5Te3 and n‐type Bi2Te2.7Se0.3 bulk thermoelectric (TE) materials are used, and a micro thermoelectric thermostat (micro‐TET) (device size, 2 × 9.3 × 1.1 mm3; leg size, 0.4 × 0.4 × 0.5 mm3; number of legs, 44) is successfully integrated into a 5G optical module with Quad Small Form Pluggable 28 interface. As a result, the internal temperature of this kind of optical module is always maintained at 45.7°C and the optical power is up to 7.4 dBm. Furthermore, a multifactor design roadmap is created based on a 3D numerical model using the ANSYS finite element method, taking into account the number of legs (N), leg width (W), leg length (L), filling atmosphere, electric contact resistance (Rec), thermal contact resistance (Rtc), ambient temperature (Ta), and the heat generated by the laser source (QL). It facilitates the integrated fabrication of micro‐TET, and shows the way to enhance packaging and performance under different operating conditions. According to the roadmap, the micro‐TET (2 × 9.3 × 1 mm3, W = 0.3 mm, L = 0.4 mm, N = 68 legs) is fabricated and consumes only 0.89 W in cooling mode (QL = 0.7 W, Ta = 80°C) and 0.36 W in heating mode (Ta = 0°C) to maintain the laser temperature of 50°C. This research will hopefully be applied to other microprocessors for precise temperature control and integrated manufacturing.

Acoustic propagation modeling using sound velocity profiles estimated from high resolution temperature data

An accurate sound velocity profile (SVP) is an important input for underwater acoustic propagation modeling. The SVP is largely driven by the temperature of the water column, especially at shallower depths. Measuring the SVP in high spatial and temporal resolution is challenging with traditional instrumentation, however techniques exist to produce high resolution temperature measurements that can be used to derive estimates of the SVP. Fiber optic distributed temperature sensing (DTS) offers an improvement of several orders of magnitude over traditional singular point measurement devices and has the ability to measure temperature over large range and depth scales in an efficient manner. A DTS system was towed for 172 nm off the coast of New England over several days. The measured temperature data was used to estimate the SVP across the range and depth and will be compared to traditional environmental data sets, such as HYCOM. A comparison of modeled acoustic propagation using different resolution SVPs will be presented.

Optical Temperature Sensor Evaluation in a Working Gear Motor: Application of Luminescence Thermometry in Industrial Technology

Abstract3D printing constitutes a technological advancement, revolutionizing contemporary industry by enabling manufacturers to fabricate intricate, customized components efficiently and precisely from digital blueprints. Moreover, the fusion of 3D printing with cutting‐edge materials has given rise to compelling elements boasting a diverse range of applications. For this reason, this work describes the incorporation of a luminescent material, NaYF4, doped with Yb3+ and Er3+, embedded in resin for 3D printing to create motorized luminescent gears. The fabricated luminescent gears take advantage of the intensity ratio between the Er3+ emissions at 525 nm (2H11/2 → 4I15/2) and 550 nm (4S3/2 → 4I15/2), which are thermally coupled, to detect the slight temperature variations that gears undergo through friction. This technique can be complementary to thermovision, proving especially valuable for monitoring temperature in elements where measurement with thermographic cameras or direct contact thermometers is hampered. The findings demonstrate that optical measurements provide enhanced (statistical) precision in temperature readings compared to thermovision, with δT = 0.07 K for luminescence thermometry as opposed to δT = 0.3 K for the thermal camera. This work can inspire new research directions using 3D printing and materials with exciting properties, fostering innovative solutions in contemporary industrial technologies.

Seawater Dual Parametric Fiber Optic Temperature and Pressure Sensors Demodulated by Machine Learning Method

By employing polydimethylsiloxane (PDMS) characterized by elevated thermo-optical and elastic-optical coefficients for encapsulating an optical microfiber coupler integrated with a sagnac loop (OMCSL) structure, which exhibits large abrupt field characteristics, a fiber optic sensor capable of simultaneously measuring seawater temperature and pressure can be created. Nevertheless, the utilization of the traditional sensitivity matrix method (SMM) for demodulating the sensor led to unstable and considerably erroneous demodulation results. To enhance the accuracy of the demodulation process, this paper investigates and employs a machine learning method (MLM) for sensor demodulation. This paper centers on the investigation and application of MLM for sensor demodulation. The experimental results exhibit a significant decrease in demodulation error attained via MLM when contrasted with the traditional SMM.

Ca3TeO6:Er3+, Yb3+ up-conversion phosphors for optical temperature sensor based on FIR technique

Ca3TeO6:Er3+, Yb3+ up-conversion phosphors for optical temperature sensor based on FIR technique

Research on denoising the temperature monitoring signal of a distributed optical fiber downhole cable

Aiming at the noise mixed in the downhole cable skin temperature signal measured by the BOTDR distributed fiber optic sensing temperature measurement system, a new improved wavelet threshold function is proposed, and denoising experiments are completed based on the MATLAB platform for the measured cable skin temperature signal. The denoising results of several threshold function methods are compared and analyzed from the aspects of graphical intuitive comparison as well as quantitative evaluation indicators. The results show that the improved threshold function denoising fiber optic temperature monitoring signal has a higher SNR and lower RMSE, there is no obvious distortion phenomenon, and the denoising performance is significantly improved compared with the traditional threshold function, which has a high application value.

Spectroscopic studies of TeO2-based glasses doped with Sm3+ and its use as an optical temperature sensor

This study reports the synthesis and characterization of glasses in the (100-x)65TeO2-15Li2O-20ZnO + xSm2O3 system doped with Sm2O3, denoted as Sm3+: TLZ glasses, with varying doping concentrations from 0.1, 0.15, 0.2, 0.35, 0.5, and 1 mol%. The structural and optical properties, as well as the temperature dependence of luminescence, were investigated. Excitation at 405nm resulted in strong orange-red luminescence at 566, 600, and 646 nm. The local environment surrounding Sm3+ ions was explored using the intensity ratio of electric and magnetic dipole transitions. The non-radiative energy transfer between neighboring Sm3+ ions was evaluated using the Inokuti-Hirayama model, allowing for the determination of the critical transfer distance. The temperature dependence of luminescence, displayed by Commission Internationale de L’Eclairage (CIE) chromaticity coordinates, exhibited a monotonic change from (0.611, 0.387) at 295 K to (0.605, 0.393) at 479 K. The Sm3+:TLZ glasses doped with 0.15 mol% showed the highest relative thermal sensitivity of 0.10%K-1 at 479 K, suggesting their potential as luminescent thermometers.

Optical method for direct temperature measurement of high intensity focused ultrasound heating

The acoustic pressure field or heat deposition from the passage of an ultrasonic wave can produce a perceptible alteration in the medium’s optical refractive index. With proper placement of the light source and imaging camera, the optical effect can be recorded. This talk describes an optical temperature measurement methodology dubbed laser-ray-bundle (LRB) of the heat deposition from a high intensity focused ultrasound (HIFU) transducer in a transparent tissue phantom. The method does not require calibration, and directly converts the thermo-optic signal to temperature without recourse to any iterative computations. LRB boasts of excellent temporal and spatial resolutions and high temperature sensitivity better than any fine wire thermocouple. Furthermore, it is completely non-invasive. The LRB method is demonstrated with the heat deposition from single millisecond long HIFU pulses in a PDMS tissue phantom or from a train of single pulses with very good performance. The method represents a new capability for quickly assess a HIFU transducer output, and for laboratory and preclinical studies of heating near tissue interfaces including bone, air, or fat. A preliminary experimental setup for measuring the acoustic pressure field is presented.

High-sensitivity optical fiber SPR temperature sensing probe based on Au-PDMS@Au coating

To enhance the sensitivity of polydimethylsiloxane (PDMS)-based optical fiber surface plasmon resonance (SPR) temperature sensing probes, we propose a new prototype with a PDMS@Au sensing layer on the gold (Au) film of the multi-mode fiber (MMF)-single-mode fiber (SMF)-MMF heterojunction structure. This designed probe has improved the temperature sensitivity from −1.26 nm/°C (Au-PDMS) to −2.14 nm/°C (Au-PDMS@Au), maintaining good repeatability and stability. Moreover, the probe can be fabricated with simple procedures at a low cost. Therefore, this probe is a promising tool for temperature sensing in various applications.

Research on key technology to determine the exact maximum allowable current-carrying ampacity for submarine cables

The maximum allowable current-carrying ampacity (MACCA) of a photoelectric composite submarine cable in its design phase is usually patterned considering the weather. However, variations in sea temperature, the uncertainty of the cable's material parameters and the laying environment of the cable greatly influence its CCA. The impact of these factors can damage the cable, regardless of its quality. For this purpose, this paper proposes a developed iterative parameters correction method (IPCM) based on Chord principles, to determine the exact MACCA by means of finite element method (FEM). Different optical fiber temperatures of the cable are collected using Brillouin Optical Time-Domain Analysis (BOTDA); together with the material parameters of the cable, they are modeled in ANSYS modeling software. Then, the proposed approach is conducted before determining the exact MACCA. Results obtained from experiments performed on different data groups show that the mean error rate obtained with the proposed approach is just about 3.78, while that of the other four recent approaches, including AP1, AP2, AP3 and AP4 is about 4.59, 3.96, 4.13 and 4.80, respectively.

LiGdxY1−xF4 and LiGdF4:Eu3+ Microparticles as Potential Materials for Optical Temperature Sensing

In this work, the physical characterization of LiGdxY1−xF4 (x = 0.05, 0.3, 0.7, and 1.0) and LiGdF4:Eu3+ microparticles was performed. The distribution coefficient of LiGdxY1−xF4 (x = 0.05) was determined for the first time (0.84). Based on kinetic characterization data, the LiGdF4 sample was chosen for further Eu3+ doping (0.1 and 1.0 at.%). For the LiGdF4:Eu3+ sample, Eu3+ emission was clearly observed under the excitation of Gd3+. This fact indicates an effective energy transfer from Gd3+ to Eu3+. The temperature-dependent spectral characterization of the LiGdF4:Eu3+ (1.0%) sample revealed that in the 30–250 K temperature range, a broad emission peak is evidenced. Its intensity sharply increases with the temperature decrease. We made a suggestion that this phenomenon is related to the irradiation-induced defects. The integrated luminescence intensity ratio of this broad peak and the Eu3+ emission were taken as temperature-dependent parameters. The sensitivity values are very competitive, and the first maximum occurs at 174 K (3.18%/K). The kinetic characteristics of both Gd3+ and Eu3+ did not demonstrate a notable temperature dependence. The LiGdF4:Eu3+ sample showed the possibility of being used as an optical temperature sensor, operating in the cryogenic temperature range.

Tunable Self-Referenced Molecular Thermometers via Manipulation of Dual Emission in Platinum(II) Pyridinedipyrrolide Complexes.

Optical temperature sensors based on self-referenced readout schemes such as the emission ratio and the decay time are crucial for a wide range of applications, with the former often preferred due to simplicity of instrumentation. This work describes a new group of dually emitting dyes, platinum(II) pincer complexes, that can be used directly for ratiometric temperature sensing without an additional reference material. They consist of Pt(II) metal center surrounded by a pyridinedipyrrolide ligand (PDP) and a terminal ligand (benzonitrile, pyridine, 1-butylimidazol or carbon monoxide). Upon excitation with blue light, these complexes exhibit green to orange emission, with quantum yields in anoxic toluene at 25 °C ranging from 13% to 86% and decay times spanning from 8.5 to 97 μs. The emission is attributed to simultaneous thermally activated delayed fluorescence (TADF) and phosphorescence processes on the basis of photophysical investigations and DFT calculations. Rather uniquely, simple manipulations in substituents of the PDP ligand and alteration of the terminal ligand allow fine-tuning of the ratio between TADF and phosphorescence from almost 100% TADF emission (Pt(MesPDPC6F5(BN)) to over 80% of phosphorescence (Pt(PhPDPPh(BuIm)). Apart from ratiometric capabilities, the complexes also are useful as decay time-based temperature indicators with temperature coefficients exceeding 1.5% K-1 in most cases. Immobilization of the dyes into oxygen-impermeable polyacrylonitrile produces temperature sensing materials that can be read out with an ordinary RGB camera or a smartphone. In addition, Pt(PhPDPPh)Py can be incorporated into biocompatible RL100 nanoparticles suitable for cellular nanothermometry, as we demonstrate with temperature measurements in multicellular colon cancer spheroids.

Controlling the Optical Properties of Transparent Auxetic Liquid Crystal Elastomers.

Determining the tunability of the optical coefficients, order parameter, and transition temperatures in optically transparent auxetic liquid crystal elastomers (LCEs) is vital for applications, including impact-resistant glass laminates. Here, we report measurements of the refractive indices, order parameters, and transition temperatures in a family of acrylate-based LCEs in which the mesogenic content varies from ∼50 to ∼85%. Modifications in the precursor mixture allow the order parameter, ⟨P2⟩, of the LCE to be adjusted from 0.46 to 0.73. The extraordinary refractive index changes most significantly with composition, from ∼1.66 to ∼1.69, in moving from a low to high mesogenic content. We demonstrate that all LCE refractive indices decrease with increasing temperature, with temperature coefficients of ∼10-4 K-1, comparable to optical plastics. In these LCEs, the average refractive index and the refractive index anisotropy are tunable via both chemical composition and order parameter control; we report design rules for both.

Analysis of heat consumption and nutritional requirements in sports based on optical imaging technology and temperature sensors

Analysis of heat consumption and nutritional requirements in sports based on optical imaging technology and temperature sensors

Strong green up-conversion luminescence and optical thermometry of Ho3+/Yb3+ Co-doped AlN submicron towers

Rare-earth (RE) doped aluminum nitride (AlN) holds great promise for integrated optoelectronic devices. Here, the Ho and Yb co-doped AlN (AlN:Ho3+/Yb3+) submicron towers were prepared by a direct nitridation route. XRD, Raman, XPS and EDS studies showed successful doping of Ho and Yb ions into AlN. SEM images show that the submicron towers have an interesting layered structure by layer-by-layer stacking of hexagonal AlN nanosheets. Under excitation at 980 nm, AlN:Ho3+/Yb3+ submicron towers exhibit up-conversion (UC) luminescence at 540, 550, 659, and 762 nm, which are due to Ho3+/Yb3+ system from 5F4, 5S2→5I8, 5F5→5I8, and 5F4, 5S2→5I7 respectively. Based on the intensity ratio and decay lifetime of UC luminescence, the optical temperature sensing characteristics are investigated from 298 K to 548 K. The maximum relative sensitivities associated with the intensity ratio of I540, 550 and I659 and decay lifetime of 659 nm are as high as 2.73% K−1 and 0.43% K−1, respectively. This work broadens the optoelectronic properties of RE doped AlN.

Testing the reproducibility of active-distributed temperature sensing for measuring groundwater specific discharge beneath a braided river

Braided rivers are a major contributor of groundwater recharge, yet little is known about how recharge rates vary in time. Existing methods for estimating groundwater recharge from rivers (i.e., river loss) are inadequate for studying highly heterogeneous braided river systems at a sufficient spatiotemporal resolution. To do so, active-distributed temperature sensing (A-DTS) is employed, which combines fibre optic temperature measurements with an active heat source, enabling high-resolution quantification of water fluxes. In this study, twelve successive A-DTS surveys were conducted during a 24-hour experiment on a 100 m horizontal subsurface hybrid fibre optic cable installed at 5 m depth beneath a braided river. The experiment was carried out under conditions where the river stage and flow were relatively stable to demonstrate the reproducibility and effectiveness of the A-DTS method for measuring groundwater specific discharge. This foundational work will provide a high level of confidence in the method for future studies aimed at evaluating temporal variations in groundwater recharge. The median groundwater specific discharge values calculated over the 24-hour period had a very narrow range from 3.5 to 4.0 m d−1 across the wetted footprint of the river, which is within the measurement error of the installation (6 %), indicating relatively stable groundwater recharge during the experiment. This provides confidence in the repeatability of the A-DTS method as an effective technology for quantifying river loss over longer time periods, to understand seasonal variability of groundwater recharge in braided river systems.