Jijun Xiong

Packaged silica microsphere-taper coupling system for robust thermal sensing application

We propose and realize a novel packaged microsphere-taper coupling structure (PMTCS) with a high quality factor (Q) up to 5×10(6) by using the low refractive index (RI) ultraviolet (UV) glue as the coating material. The optical loss of the PMTCS is analyzed experimentally and theoretically, which indicate that the Q is limited by the glue absorption and the radiation loss. Moreover, to verify the practicability of the PMTCS, thermal sensing experiments are carried out, showing the excellent convenience and anti-jamming ability of the PMTCS with a high temperature resolution of 1.1×10(-3) ◦C. The experiments also demonstrate that the PMTCS holds predominant advantages, such as the robustness, mobility, isolation, and the PMTCS can maintain the high Q for a long time. The above advantages make the PMTCS strikingly attractive and potential in the fiber-integrated sensors and laser.

Effects of chemical fluctuations on microstructures and properties of multiferroic BiFeO3 thin films

BiFeO3 films have been grown on SrTiO3 (001) substrates by pulsed laser deposition. It was found that oxygen partial pressure is crucial to phase purity, surface morphology, and surface chemistry. Single-phase BFO films were obtained at 1Pa O2, while Bi2O3 appeared in the films deposited at 0.01Pa as confirmed by x-ray diffractions. It was revealed that Fe2+ and metallic Bi exist in the films fabricated at 0.01Pa by x-ray photoelectron spectroscopy investigation. Owing to Fe2+ in the samples deposited at 0.01Pa, the saturation magnetization is much larger than the ones fabricated at 1Pa. A well-saturated ferroelectric hysteresis loop with a polarization of 23.6μC∕cm2 was observed in the single-phase samples. In contrast, the films deposited at 0.01Pa exhibited poor ferroelectric properties.

A wireless passive pressure microsensor fabricated in HTCC MEMS technology for harsh environments.

A wireless passive high-temperature pressure sensor without evacuation channel fabricated in high-temperature co-fired ceramics (HTCC) technology is proposed. The properties of the HTCC material ensure the sensor can be applied in harsh environments. The sensor without evacuation channel can be completely gastight. The wireless data is obtained with a reader antenna by mutual inductance coupling. Experimental systems are designed to obtain the frequency-pressure characteristic, frequency-temperature characteristic and coupling distance. Experimental results show that the sensor can be coupled with an antenna at 600 °C and max distance of 2.8 cm at room temperature. The senor sensitivity is about 860 Hz/bar and hysteresis error and repeatability error are quite low.

Fiber Surface Modification Technology for Fiber-Optic Localized Surface Plasmon Resonance Biosensors

Considerable studies have been performed on the development of optical fiber sensors modified by gold nanoparticles based on the localized surface plasmon resonance (LSPR) technique. The current paper presents a new approach in fiber surface modification technology for biosensors. Star-shaped gold nanoparticles obtained through the seed-mediated solution growth method were found to self-assemble on the surface of tapered optical fibers via amino- and mercapto-silane coupling agents. Transmitted power spectra of 3-aminopropyltrimethoxy silane (APTMS)-modified fiber were obtained, which can verify that the silane coupling agent surface modification method is successful. Transmission spectra are characterized in different concentrations of ethanol and gentian violet solutions to validate the sensitivity of the modified fiber. Assembly using star-shaped gold nanoparticles and amino/mercapto silane coupling agent are analyzed and compared. The transmission spectra of the gold nanoparticles show that the nanoparticles are sensitive to the dielectric properties of the surrounding medium. After the fibers are treated in t-dodecylmercaptan to obtain their transmission spectra, APTMS-modified fiber becomes less sensitive to different media, except that modified by 3-mercaptopropyltrimethoxy silane (MPTMS). Experimental results of the transmission spectra show that the surface modified by the gold nanoparticles using MPTMS is firmer compared to that obtained using APTMS.

A Harsh Environment-Oriented Wireless Passive Temperature Sensor Realized by LTCC Technology

To meet measurement needs in harsh environments, such as high temperature and rotating applications, a wireless passive Low Temperature Co-fired Ceramics (LTCC) temperature sensor based on ferroelectric dielectric material is presented in this paper. As a LC circuit which consists of electrically connected temperature sensitive capacitor and invariable planar spiral inductor, the sensor has its resonant frequency shift with the variation in temperature. Within near-filed coupling distance, the variation in resonant frequency of the sensor can be detected contactlessly by extracting the impedance parameters of an external antenna. Ferroelectric ceramic, which has temperature sensitive permittivity, is used as the dielectric. The fabrication process of the sensor, which differs from conventional LTCC technology, is described in detail. The sensor is tested three times from room temperature to 700 °C, and considerable repeatability and sensitivity are shown, thus the feasibility of high performance wireless passive temperature sensor realized by LTCC technology is demonstrated.

A High Temperature Capacitive Pressure Sensor Based on Alumina Ceramic for in Situ Measurement at 600 °C

In response to the growing demand for in situ measurement of pressure in high-temperature environments, a high temperature capacitive pressure sensor is presented in this paper. A high-temperature ceramic material-alumina is used for the fabrication of the sensor, and the prototype sensor consists of an inductance, a variable capacitance, and a sealed cavity integrated in the alumina ceramic substrate using a thick-film integrated technology. The experimental results show that the proposed sensor has stability at 850 °C for more than 20 min. The characterization in high-temperature and pressure environments successfully demonstrated sensing capabilities for pressure from 1 to 5 bar up to 600 °C, limited by the sensor test setup. At 600 °C, the sensor achieves a linear characteristic response, and the repeatability error, hysteresis error and zero-point drift of the sensor are 8.3%, 5.05% and 1%, respectively.

Measurement of wireless pressure sensors fabricated in high temperature co-fired ceramic MEMS technology

High temperature co-fired ceramics (HTCCs) have wide applications with stable mechanical properties, but they have not yet been used to fabricate sensors. By introducing the wireless telemetric sensor system and ceramic structure embedding a pressure-deformable cavity, the designed sensors made from HTCC materials (zirconia and 96% alumina) are fabricated, and their capacities for the pressure measurement are tested using a wireless interrogation method. Using the fabricated sensor, a study is conducted to measure the atmospheric pressure in a sealed vessel. The experimental sensitivity of the device is 2 Hz/Pa of zirconia and 1.08 Hz/Pa of alumina below 0.5 MPa with a readout distance of 2.5 cm. The described sensor technology can be applied for monitoring of atmospheric pressure to evaluate important component parameters in harsh environments.

Robust Spot-Packaged Microsphere-Taper Coupling Structure for In-Line Optical Sensors

We propose and realize a spot-packaged structure for the microsphere-taper coupling system by only encapsulating and solidifying the coupling region with low refractive index polymer as the package material. After spot-package, ultrahigh quality factor ( >; 107) is obtained with the microsphere diameters around 300 μm. The robustness of the spot-packaged structure is also tested, demonstrating the remarkable anti-tensile strength ability with the bearable loaded force larger than 0.05 N for a packaged structure with the spot-package area larger than 30 μm2. In addition, the spot-packaged structure is integrated with standard fiber, promising in in-line optical practical evanescent field sensing applications, especially in harsh detecting environments demanding high overload resistance.

Wireless Passive Temperature Sensor Realized on Multilayer HTCC Tapes for Harsh Environment

A wireless passive temperature sensor is designed on the basis of a resonant circuit, fabricated on multilayer high temperature cofired ceramic (HTCC) tapes, and measured with an antenna in the wireless coupling way. Alumina ceramic used as the substrate of the sensor is fabricated by lamination and sintering techniques, and the passive resonant circuit composed of a planar spiral inductor and a parallel plate capacitor is printed and formed on the substrate by screen-printing and postfiring processes. Since the permittivity of the ceramic becomes higher as temperature rises, the resonant frequency of the sensor decreases due to the increasing capacitance of the circuit. Measurements on the input impedance versus the resonant frequency of the sensor are achieved based on the principle, and discussions are made according to the exacted relative permittivity of the ceramic and quality factor () of the sensor within the temperature range from 19°C (room temperature) to 900°C. The results show that the sensor demonstrates good high-temperature characteristics and wide temperature range. The average sensitivity of the sensor with good repeatability and reliability is up to 5.22 KHz/°C. It can be applied to detect high temperature in harsh environment.

Polymer optical fiber twisted macro-bend coupling system for liquid level detection

The liquid level detection principle of cladding mode frustrated total internal reflection (CMFTIR) effect is proposed. The significant enhancement of CMFTIR effect is realized through macro-bend coupling system in which the dark-field coupling phenomenon between two multimode polymer optic fibers is observed through experiment. Especially twisted macro-bend coupling structure (TMBCS) is adopted to achieve stable coupling of two naked POF. The testing result showed that the dark-filed forward coupling efficiency reached 2‰ and the extinction ratio of the liquid level probe reached 4.18 dB. Compared with existing optical fiber liquid level sensors, the TMBCS probe is simpler, robuster, and cheaper. In addition, the TMBCS has the potential for displacement or stress sensing.