Chenyang Xue

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.

Design, fabrication, and preliminary characterization of a novel MEMS bionic vector hydrophone

According to the auditory principle of fishs lateral line organ, a novel microelectromechanical systems (MEMS) bionic vector hydrophone used for obtaining vector information of underwater sound field is introduced in this paper. It is desirable that the application of MEMS-based piezoresistive effect and bionics structure may improve the low-frequency sensitivity of the vector hydrophone as well as its miniaturization. The bionic structure consists of two parts: high-precision four-beam microstructure and rigid plastic cylinder which is fixed at the center of the microstructure. The piezoresistor located at the beam is simulated to the hair cell of lateral line and the rigid plastic cylinder is simulated to stereocilia. When the plastic cylinder is stimulated by sound, the piezoresistor transforms the resultant strain into a differential voltage output signal via the Wheatstone bridge circuit. Microfabrication technology has been employed for the fabrication of the microstructure and measurement results are given. The experiment results show that the receiving sensitivity of the hydrophone is -197.7dB (0dB=1V/@mPa). The novel hydrophone not only possesses satisfactory directional pattern as well as miniature structure, but also has good low-frequency characteristics, and satisfies the requirements for low-frequency acoustic measurement.

Highly Stretchable Electrodes on Wrinkled Polydimethylsiloxane Substrates.

This paper demonstrates a fabrication technology of Ag wrinkled electrodes with application in highly stretchable wireless sensors. Ag wrinkled thin films that were formed by vacuum deposition on top of pre-strained and relaxed polydimethylsiloxane (PDMS) substrates which have been treated using an O2 plasma and a surface chemical functionalization process can reach a strain limit up to 200%, while surface adhesion area can reach 95%. The electrical characteristics of components such as resistors, inductors and capacitors made from such Ag conductors have remained stable under stretching exhibiting low temperature and humidity coefficients. This technology was then demonstrated for wireless wearable electronics using compatible processing with established micro/nano fabrication technology.

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.

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.

Fano Resonance Based on Metal-Insulator-Metal Waveguide-Coupled Double Rectangular Cavities for Plasmonic Nanosensors

A refractive index sensor based on metal-insulator-metal (MIM) waveguides coupled double rectangular cavities is proposed and investigated numerically using the finite element method (FEM). The transmission properties and refractive index sensitivity of various configurations of the sensor are systematically investigated. An asymmetric Fano resonance lineshape is observed in the transmission spectra of the sensor, which is induced by the interference between a broad resonance mode in one rectangular and a narrow one in the other. The effect of various structural parameters on the Fano resonance and the refractive index sensitivity of the system based on Fano resonance is investigated. The proposed plasmonic refractive index sensor shows a maximum sensitivity of 596 nm/RIU.

Refractive Index Sensor Based on Fano Resonances in Metal-Insulator-Metal Waveguides Coupled with Resonators

A surface plasmon polariton refractive index sensor based on Fano resonances in metal–insulator–metal (MIM) waveguides coupled with rectangular and ring resonators is proposed and numerically investigated using a finite element method. Fano resonances are observed in the transmission spectra, which result from the coupling between the narrow-band spectral response in the ring resonator and the broadband spectral response in the rectangular resonator. Results are analyzed using coupled-mode theory based on transmission line theory. The coupled mode theory is employed to explain the Fano resonance effect, and the analytical result is in good agreement with the simulation result. The results show that with an increase in the refractive index of the fill dielectric material in the slot of the system, the Fano resonance peak exhibits a remarkable red shift, and the highest value of sensitivity (S) is 1125 nm/RIU, RIU means refractive index unit. Furthermore, the coupled MIM waveguide structure can be integrated with other photonic devices at the chip scale. The results can provide a guide for future applications of this structure.

Integrated high sensitivity displacement sensor based on micro ring resonator

A novel integrated high sensitivity displacement sensor based on micro ring resonator is described. It includes the high sensitivity of optical sensors and the compactness and potential for mass production of the MEMS sensors. In this design, GaAs-Al0.6Ga0.4As platform was chose for its high-index contrast. A bus waveguide couples to a micro ring resonator and they are integrated on the supporting point of a cantilever. We can obtain the value of displacement sensor by means of monitoring the changes in the transmission spectrum of the ring resonator due to the photo-elastic effect and the change of circumference as the deformation of cantilever. This method has high sensitivity and can be used in harsh environments such as ultra-high vacuum (UHV) systems and electromagnetically active environments. Finite Element Method (FEM) simulations were carried out to obtain the optimum sensor design and Beam Propagation Method (BPM) simulation was used to obtain the transfer characteristics of the bus waveguide and the micro ring resonator. In this paper, operation principles and sensitivity analysis are discussed in detail. Different types of ring resonators are studied in order to achieve high sensitivity and the radius of 20µm of ring resonator is chose eventually. Further more, because of the fabrication limit, the FIB (Focused Ion Beam) is used to etch the gap between waveguide and ring resonator accurately after RIE etching, which can control the gap to less than 100nm, and the whole manufacturing process is also presented.