High-sensitivity Temperature Sensor Research Articles

A novel optical temperature sensor based on Boltzmann function in BiZn2PO6 phosphor

In this paper, a new scheme of optical temperature measurement based on Boltzmann function is reported for the first time. The BiZn2PO6 and BiZn2PO6:Eu3+ phosphors with strong host emission intensity were investigated from the perspective of crystal structure, electronic band structure, phonon distribution, and fluorescence properties. By exploring the relationship between host emission intensity and temperature, or between fluorescence lifetime and temperature, a novel optical temperature sensor based on Boltzmann function was designed. With this scheme, the performance of the optical temperature sensors can be visualized in the fitting results of Boltzmann function. The absolute sensitivity of the optical temperature sensor designed based on this function reaches a maximum value Sa=14dT at T0, while relative sensitivity is 12dT. For example, in BiZn2PO6 phosphor, the absolute and relative sensitivities reached 0.88% and 1.78% at 260 K. Therefore, the new optical temperature sensor based on Boltzmann function provides the theoretical basis and practical experience for the development of high-sensitivity non-contact optical temperature sensor.

Inhomogeneous heterojunction performance of Zr/diamond Schottky diode with Gaussian distribution of barrier heights for high sensitivity temperature sensor

Herein, we demonstrated the fabrication and operation of vertical diamond Schottky barrier diode (SBD) as a high-performance temperature sensor. The current transport mechanism and temperature sensor properties of Zr/p-diamond SBD were comprehensively investigated with operating temperatures up to 448 K. At room temperature, Zr/p-diamond SBD exhibits outstanding performances with a high rectification ratio of 2.28 × 1010, a low specific on-resistance of 0.5 mΩ•cm2, a large Schottky barrier height (SBH) of 1.43 eV, a low ideality factor of 1.77, and an extremely low saturation current of 4.42 × 10−22 A. The enhanced-performance with a higher forward current and a lower reverse leakage current is observed to be across a wide temperature range from 323 to 448 K. Additionally, a significant improvement of rectifying current curve with a highest rectification ratio over 1012 is obtained at 423 K. The SBH increases whereas the ideality factor decreases with temperature increasing, indicating barrier inhomogeneities at Zr/p-diamond interface. The temperature-dependent electrical transport characteristics on spatially inhomogeneous Schottky contacts can be successfully described by potential fluctuations model. The extracted original value of Richardson constant (A*) is 0.0153 A/cm2•K2, which is much lesser than theoretical value of 96 A/cm2•K2. The discrepancy of A* value from theoretical value has been well explained by thermionic emission model with Gaussian distribution of barrier inhomogeneity. The values of mean SBH and A* extracted from modified Richardson plot depending on SBH inhomogeneity are 1.76 eV and 105.51 A/cm2•K2, respectively. With a Gaussian distribution take into account, the A* value is close to the theoretical value, and confirmed the existence of SBH inhomogeneity at Zr/p-diamond interface. Furthermore, for Zr/p-diamond SBD operating as a temperature sensor, the voltage drop across the diode decreases linearly with increasing temperature at a specific forward current level, contributing to a highest sensor sensitivity of 6.8 mV/K. The reported results in this work are among the best to date in diamond SBD temperature sensor. Although not optimized for temperature sensor, the high and thermally stable rectifying barriers make Zr/p-diamond SBD a strong candidates for high-performance diamond rectifying diode and temperature sensor.

Nano optical temperature sensor based on fiber Bragg grating using graphene

In this paper, a novel Graphene-Assisted Microfiber based temperature sensor is proposed that changing the surrounding temperature has a severe effect on the refractive index of the graphene, so these changes result in the transmission power of microfiber. In the proposed structure, the position of the graphene sheet affects the interaction of light and graphene, effectively. Simply, by examining the change in transmission power, the temperature sensitivity of 0.1038 dBC in the heating process and 0.1072 dBC in the high-resolution cooling process of 0.0098 ℃ is obtained, which is 16 times more than bare fiber. Moreover, in this paper, both MgF2 layer and the graphene ribbon affect fiber refractive index so a high sensitivity, compact size, low cost, linear operation and suitable transmission coefficient temperature sensor is achieved. This sensor has great potential in the field of measurement, especially surrounding temperature measurement. Also, a comprehensive and detailed study of the properties of surface conductivity, electric dispersion, refractive index and permittivity for graphene with sensitivity simulation is accomplished.

High-sensitivity temperature sensor based on Mach–Zehnder interferometer filled with dimethyl silicone oil

In this paper, a high-sensitivity temperature sensor based on the Mach–Zehnder interferometer (MZI) is designed and verified by experiments. The MZI is a splicing structure of ‘single mode fiber–multimode fiber–quartz capillary–multimode fiber–single mode fiber’. A microchannel was fabricated on the walls of the capillary by femtosecond laser pulses, and dimethyl silicone oil (DSO) was injected into the capillary by the immersion method. When filled with DSO, the microchannel is sealed with epoxy adhesive to form a MZI temperature sensor. When the ambient temperature changes, the DSO in the capillary of the MZI has a very high thermo-optical effect, resulting in a change in the optical path difference in the MZI and a large wavelength shift in the transmission spectrum of the MZI. Therefore, high temperature sensitivity can be obtained by demodulating the wavelength shift of the MZI transmission spectrum. The experimental results show that the temperature sensitivity of the MZI filled with DSO is 7.421 nm °C−1 in the range of 30 °C–50 °C, which is 297 times that of the MZI without DSO (0.025 nm °C−1). In addition, the sensor has a compact structure, robustness, good repeatability and stability.

Temperature sensing based on multimode interference in polymer optical fibers: sensitivity enhancement by PC-APC connections

A simple, stable, and high-sensitivity temperature sensor based on multimode interference in a polymer optical fiber (POF) with higher-order mode excitation has been developed. In a single-mode–multimode–single-mode (SMS) structure, one end of the multimode POF with physical-contact (PC) connectors is connected to a silica single-mode fiber with an angled-PC (APC) connector. We compare the temperature sensing characteristics of the three configurations (no PC-APC, PC-APC at input, and PC-APC at output) and obtain the highest temperature sensitivity of 219.2 pm °C−1, which is more than double the value of the standard (no PC-APC) SMS structure.

Temperature dependent studies on centimeter-scale MoS2 and vdW heterostructures

Transition metal dichalcogenides is an emerging 2D semiconducting material group which has excellent physical properties in the ultimately scaled thickness dimension. Specifically, van der Waals heterostructures hold the great promise in further advancing both the fundamental scientific knowledge and practical technological applications of 2D materials. Although 2D materials have been extensively studied for various sensing applications, temperature sensing still remains relatively unexplored. In this work, we experimentally study the temperature-dependent Raman spectroscopy and electrical conductivity of molybdenum disulfide (MoS2) and its heterostructures with platinum dichalcogenides (PtSe2 and PtTe2) to explore their potential to become the next-generation temperature sensor. It is found that the MoS2-PtX2 heterostructure shows the great promise as the high-sensitivity temperature sensor.

Enhanced Temperature Sensing Based on the Randomness in the Multilayered 1D Photonic Crystals

A high sensitive temperature sensor is proposed based on the random properties of the one dimensional photonic crystal (1DPC). The structure is designed with two layers consisting of silicon (Si) and silica (SiO2) materials. The transmission spectra of the photonic crystals are studied at different temperatures from 25°C to 100°C. Thermal characteristics of the proposed random structures are examined with the effect of thermal expansion and thermo-optic effect. As the temperature increases the transmission peak shifts towards the longer wavelength due to the thermal parameters of the dielectrics used. It is found that the temperature-sensitive transmission peak shift is significantly improved due to the insertion of the third material that constitutes the ternary photonic structure (Si/SiO2/TiO2)N. For the above multilayer structures, based on the dependence of the layer thickness and the number of materials used, the numerical results show a sensitivity of 0.052nm/°C. When the third dielectric material (TiO2) is replaced by the polymer material (PS), the wavelength of the transmittance peak shift can be enhanced to 0.087nm/°C. These properties are useful for the fabrication of handy temperature sensors.

Ultrahigh-sensitivity SPR fiber temperature sensor based Ge2Sb2Te5 and cyclohexane

High-sensitivity fiber optic temperature sensors are essential analytical tools in biological and chemical fields. To increase the temperature sensitivity of the surface plasmon resonance sensors, we decide to employ a stable material, Ge2Sb2Te5 (GST). When GST is deposited on the gold film's surface, SPR is excited at lower frequency, this indicates that the resonance dips are red-shifted. At long wavelengths, the evanescent field is greatly enhanced, and the penetration depth is increased, which increases the interaction volume. In other words, the sensitivity is greatly improved. The fiber optic is encapsulated in cyclohexane with a high thermo-optic coefficient and a high refractive index. The sensitivity improves further because the fiber is placed in a high refractive index environment. The sensor's average temperature sensitivity is 14.7 nm/°C, with a measurement range of 5 °C to 80 °C, according to the output spectra. The maximum temperature sensitivity can reach 25.7 nm/°C. As a result, the suggested temperature sensor might be useful in various industries that need high measurement precision.

Comparison of High-Sensitivity Plasmonic Temperature Sensor Based on Photonic Crystal Fiber

Comparison of High-Sensitivity Plasmonic Temperature Sensor Based on Photonic Crystal Fiber

Experimental study of a tapered fiber temperature sensor with a liquid seal based on multimode interference

Studying high-sensitivity fiber-optic temperature sensors is vital in pursuing high-precision temperature measurement. We propose a liquid-sealed multimode interference fiber temperature sensor with a double-taper structure. The influence of structure and sealed-liquid material on the temperature sensitivity of the sensor is analyzed experimentally. The results show that the tapered structure can effectively improve the temperature sensitivity of the sensor, and the effect becomes more evident with the increased refractive index of the sealed liquid. As the refractive index of the sealed liquid increases, the temperature sensitivity of the sensor can be effectively improved. However, the sealed liquid with a high refractive index will increase the failure temperature of the sensor. Near the failure temperature, the sensor achieves an ultra-high-temperature sensitivity of -8.28nm/K. The results also prove that further increasing the refractive index of the sealed liquid no longer has a significant gain in temperature sensitivity. It is expected that the relevant research will contribute to the development of high-precision temperature-sensing systems.

Numerical and experimental study on temperature measurement performance of SNS fiber optic sensor with liquid-sealed

Single-mode-no-core-single-mode (SNS) optical fiber structures have valuable potential to encapsulate as high-precision temperature sensors, due to their great sensitivity. This paper is to improve the temperature sensitivity of SNS fibers by studying the parameters of fiber length, diameter, and refractive index of the seal liquid. Transmission spectra of the fibers are given in both aspects of experiment and numerical simulation. We find that using a slim no-core fiber section sealed with liquid of high refractive index can effectively improve the sensitivity, while the choice of fiber length mainly affects the width of transmission peak. The results may contribute to the development of high-sensitivity optic temperature sensor.

High-sensitivity temperature sensor based on Mach-Zehnder interference of asymmetric taper-shaped ultraviolet glue

In this paper, a Mach-Zehnder interference (MZI) based on asymmetric taper-shaped ultraviolet glue is proposed for highly sensitive temperature sensing. Due to the small diameter and the deflected two ends of the tapered UV glue, part of the light leaked into the air during the propagation of the UV glue taper, resulting in interference. We tested the temperature sensing of several samples with different parameters. Experimental results show that with the increase of temperature, the wavelength moves linearly to a shorter wavelength. The highest temperature sensitivity can reach −15 nm/℃, and the linear correlation coefficient is 0.995. The sensor has the advantages of low cost, simple manufacture and higher temperature sensitivity is suitable for temperature measurement.

Sensitivity-enhanced temperature sensor by cascaded configuration of polarization mode interferometer and Lyot filter based on Vernier effect

We proposed and experimentally demonstrated a novel high-sensitivity optical fiber temperature sensor (OFTS) which is composed of the Lyot filter cascading a polarization mode interferometer (PMI). The Lyot filter is fabricated by inserting a polarization-maintaining fiber (PMF) between two linear fiber polarizers at two 45-degree angles. By simply cleaving the end fiber of the PMI, the free spectral range (FSR) can be maximized to approach the FSR of the Lyot filter, which introduces the Vernier effect. Experimental results show that the cascaded sensor can provide high-temperature sensitivity of 10.666 nm/°C and 26.562 nm/°C, which are 6.71 and 12.168 times that of single PMI, respectively. The method is demonstrated to achieve a stable and controlled Vernier effect obtaining ultra-high temperature sensitivity, which agrees well with the theoretical simulation results. The proposed sensor has the advantages of high sensitivity, good stability, and easy fabrication.

High-Sensitivity Thermal Sensing Based on a Single Strain-Assisted Resonator

Microresonator-based temperature sensors offer stable and high-resolution temperature detection. However, typical temperature-sensing techniques based on resonators suffer from design complexity and low sensitivity. In this study, we present a simple high-sensitivity temperature sensor that comprises a sealed electrostatically actuated clamped–clamped silicon microbeam resonator. The sensor’s high sensitivity is attributed to the thermal-strain effects due to the mismatch between the thermal expansion coefficients of the composite materials. And the sensitivity is further enhanced by operating the resonator near the buckling zone via in situ Joule heating. In addition, The sensor operates at a single drive frequency that corresponds to the resonant frequency at the maximum temperature. A change in temperature induces a thermal strain that shifts the resonant frequency, which changes the output voltage. This considerably simplifies the readout system from the typical frequency-tracking method to the proposed amplitude tracking method. The encapsulated sensor achieves a minimum detectable temperature of 0.0196 °C and an absolute temperature coefficient of frequency of 1757 ppm/°C. These results demonstrate the great potential of the proposed sensor for efficient resonant thermal sensing with high resolution, enhanced sensitivity and a simplified readout scheme.

Novel optical temperature sensors based on the emission of the Pr3+ ions doped Ca3(M,Ga)5O12 (M5+ = Nb, Ta) garnet phosphors

Pr3+-doped Ca3(Nb,Ga)5O12 (Pr:CNGG) and Ca3(Ta,Ga)5O12 (Pr:CTGG) phosphors with garnet structure have been systematically investigated as optical thermometric materials for potential applications in the field of sensing technology, for the first time to our knowledge. The ceramic samples of Pr:CNGG and Pr:CTGG with different concentrations of Pr3+ ions have been obtained by the solid-state reaction method. A comparative analysis to evidence the influence of the position of the inter-valence charge transfer (IVCT) states on the excited-state dynamics of Pr3+ ions in CNGG and CTGG materials is presented. The optical thermometric properties of the Pr:CNGG and Pr:CTGG samples were studied. The luminescence thermal quenching mechanisms of the 3P0 and 1D2 levels were investigated in detail based on the luminescence intensity ratio (LIR) of 1D2→3H4 / 3P0→3H4 (I606/I487) transitions over an extended temperature range (10–700 K). The maximum relative sensitivities were determined to be 1.64% K−1 at 10 K for 7 at% Pr:CTGG and 2.4% K−1 at 430 K for 1 at% Pr:CNGG, thus proving their potential as high-sensitivity temperature sensors in cryogenic and high-temperature domains, respectively.

Strain-insensitive high-sensitivity temperature sensing based on multimode interference in a square-core fiber

A strain-insensitive high-sensitivity temperature sensor based on multimode interference in a specialty fiber with a square core is developed and experimentally investigated. A 25 cm long square-core fiber is used as a multimode fiber (MMF) of a single-mode–multimode–single-mode structure and the temperature dependence of its transmitted spectrum is measured while the strain is applied continually from 0 to 500 με with steps of 100 με. The mean temperature sensitivity is −22.35 pm °C−1, which is ∼3.5 times higher than that of a standard MMF, and it is almost independent of strain with a small standard deviation of 0.44 pm °C−1.

High-Sensitivity Temperature Sensor Based on Two Parallel Fabry–Pérot Interferometers and Vernier Effect

High-Sensitivity Temperature Sensor Based on Two Parallel Fabry–Pérot Interferometers and Vernier Effect

Passive RFID microstrip antenna sensor for temperature monitoring

In this paper, an ultra-high-speed and high-sensitivity temperature sensor based on a microwave band-stop filter modified with ZnO/MoS2/RGO nanocomposite materials is designed and manufactured. The amplitude of the temperature in the environment is determined in the frequency band from 2.73 GHz to 2.76 GHz. The optimized microstrip patch temperature sensor obtains a higher response and better quality factor, which improves the sensitivity of the temperature sensor. In order to study the performance of the temperature sensor, the sensor element modified with molybdenum disulfide (MoS2) sensitive material was placed in the radiosonde detection box, and the temperature level test was realized under the same humidity environment. The measurement results show that the amplitude change of the insertion loss from 0 °C to 200 °C shows a horizontal linear change. In addition, the temperature response recovery time is less than 10 s, and the temperature hysteresis is less than 0.34 °C. This paper also discusses the mechanism of microstrip temperature-sensitive sensing from the perspective of molecular polarization. This provides a simple and easy method for realizing a high-sensitivity, fast-response microstrip temperature sensor.

Ultra-High-Sensitive Temperature Sensing Based on Er3+ and Yb3+ Co-Doped Lead-Free Double Perovskite Microcrystals

Fluorescence intensity ratio (FIR) thermometry, a new contactless temperature measurement, can achieve accurate measurements in a harsh environment. In this work, all-inorganic lead-free Cs2AgInCl6: Er-Yb and Cs2AgBiCl6: Er-Yb microcrystals emit bright green up-conversion emission, which are synthesized by precipitation at a low temperature (80 °C). In up-conversion emission, FIR of the 2H11/2 → 4I15/2 band to the 4S3/2 → 4I15/2 band exhibits temperature dependence, which can be used as the temperature measurement parameter, so-called FIR thermometry. Moreover, the theoretically accurate measurement range is from 100 to 600 K, achieving maximum absolute sensitivities from 0.0130 to 0.0113 K-1, respectively. The principle of up-conversion and high sensitivity is well explained by calculating the partial density of states. Compared to the reported thermometry materials based on the FIR method, the prepared all-inorganic lead-free Cs2AgInCl6: Er-Yb and Cs2AgBiCl6: Er-Yb microcrystals show outstanding temperature measurement width and sensitivity, becoming a potential candidate for high-sensitivity optical temperature sensors.

High-sensitive temperature sensor with parallel PDMS-filled FPIs based on dual Vernier effect

A novel high-sensitive temperature sensor with parallel polydimethylsiloxane (PDMS)-filled Fabry–Perot interferometers (FPIs) based on dual Vernier effect was proposed and demonstrated. The sensor is composed of two parallel FPIs with similar free spectrum range fabricated by splicing a section of silica tube to single-mode fiber. One is partially filled with PDMS to form an air cavity, and the other is fully filled with PDMS to form a PDMS cavity. Owing to the difference structures of two FPIs and the excellent characteristics of PDMS, the reflective spectra of two FPIs shift to opposite directions with the changes of ambient temperature. Two FPIs serve as reference FPI for each other in temperature measurement, resulting in the dual Vernier effect to enhance Vernier effect. The experimental results show that the proposed sensor exhibits a high temperature sensitivity of 7.61 nm/°C with good linearity. This work provides a new strategy for the fiber-optic sensing field.