Yong Zhu

Magnetoelectric Performances in Composite of Piezoelectric Ceramic and Ferromagnetic Constant-Elasticity Alloy

A high-quality factor magnetoelectric (ME) laminated composite employing a type of ferromagnetic constant-elasticity alloy (FCEA) and piezoelectric Pb(Zr,Ti)O3 material is developed. The laminate is designed to operate as a half-wavelength (lambda/2), longitudinal resonator. The FCEA features high effective quality factor and low magnetomechanical coupling coefficient. This induces a particular ME characteristic. The theoretical analysis shows that the ME voltage coefficient (MEVC) at low frequency is directly proportional to the product of the electromechanical coupling factor in piezoelectric layer, magnetomechanical coupling factor, and the square root of magnetic permeability in FCEA layers. The MEVC at resonance and the ME sensitivity (under resonant drive) to dc bias magnetic field (H dc) are dramatically increased by the effective quality factor (Qm) of the resonator. The measured vibrational characteristics reveal that the strain coefficient at resonance achieves 314.74 nm/A and Qm is ~ 1600. The MEVC at resonance (alphar) achieves 30.55 V/Oe (381.875 V/cm Oe), which is 1608 times higher than that at low frequency. In addition, alphar strongly depends on H dc due to the high Qm, e.g., partalphar/partH dc achieves 0.84 V/Oe2. The ME resonator is potential for highly sensitive dc or quasi-static magnetic field sensing.

One-to-Multipoint Laser Remote Power Supply System for Wireless Sensor Networks

A method to use laser to supply power remotely for multinode wireless sensor networks is proposed in this paper. In the working space of wireless sensor networks, laser is transformed to a spatial distributed light field with certain uniformity and its wavelength is converted to the most sensitive wavelength of solar cell by the phosphor element. Thus, more wireless sensor networks nodes can be powered at the same time. A demonstration experiment is carried out, an yttrium aluminum garnet phosphor element is stimulated by the 3 W 457 nm laser and a uniform diffused light field with 3 π/4 space angle is obtained. The average optical energy density is 85 μ W/cm2 at the distance 1.5 m away from the phosphor surface. An ultra low-power consumption energy harvesting system is designed. Under the radiation of remote laser power supply, characteristics of the energy harvesting system are tested. The result is that the system can supply 92.1 mJ during 0.7 s which can provide enough energy for WSN node. Preliminary result of a real-life application in an oil cellar is also given. As a novel power supply method for wireless sensor networks, it is a good active power supply candidate for wireless sensor networks when the environment energy field is not strong enough.

Highly Sensitive Optical Refractometer Based on Edge-Written Ultra-Long-Period Fiber Grating Formed by Periodic Grooves

An ultra-long-period fiber grating with periodic groove structure (G-ULPFG) fabricated by using an edge-written method with high-frequency CO2 laser pulses is proposed in this paper. The experimental results show that the different resonant peaks of the G-ULPFG have different temperature and refractive index sensitivities and, in particular, the refractive index sensitivity is much larger than that of conventional ULPFG due to the edge-groove structure. Such a kind of G-ULPFGs could be used as a highly sensitive optical refractometer with temperature self-compensation.

Temperature dependences of photoluminescence and electroluminescence spectra in light-emitting diodes

The temperature influence on the luminescence characteristics of light-emitting diodes (LEDs) is investigated to reveal the connection of photoluminescence (PL) with photon absorption and electroluminescence (EL) through current injection. By inspecting the PL and EL spectra at identical injection intensities, it has been found that the normalized spectra in PL and EL exhibit obvious similarities in shape and apparent differences in spectral characteristic values. Furthermore, the differences are found to originate from the junction temperatures in diverse injection modes. The observations are conducted on AlGaInP red LED chips.

High sensitive magnetic transducer consisting of PZT, Terfenol-D and ultrasonic horn with high Q value

This paper presents a new magnetoelectric (ME) composite transducer consisting of a magnetostrictive Terfenol-D plate, multiple piezoelectric PZT plates and an ultrasonic horn. The energy of the vibrating wave induced from the magnetostrictive Terfenol-D plate can be converged by using an ultrasonic horn and the more vibrating energy can convert into electric energy through PZT plates at positions with a higher vibrating magnification. The composite structure with a high-Q ultrasonic horn can decrease the energy loss and gather up the energy at resonance. A higher ME voltage coefficient may be obtained by an ultrasonic horn with a higher quality (Q) value. The composite with multiple PZT plates electrically connected in series/parallel exhibits a higher ME voltage coefficient than the previous laminate composite of PZT and Terfenol-D plates. We demonstrate that the composite of several PZT plates, a Terfenol-D plate and an ultrasonic horn substrate has a significantly enhanced ME voltage coefficient and sensitivity relative to the prior sandwiched laminate composite configurations.