适于InGaAsP光放大器偏振不灵敏的增益介质

研制了适于InGaAsP光放大器偏振不灵敏的增益介质 ,采用有源区内交替的张应变和压应变排列的混合应变量子阱结构 ,器件做成带有倾角的扇形。实验中发现该结构既抑制了激射又改善了器件的偏振灵敏性 ,实现了偏振灵敏度小于 0 5dB ,10 0mA偏置时可达 0 1dB。在较大的电流范围内 ,峰的半高全宽 (FWHM)为 4 0nm。     

Fast trilayer polypyrrole bending actuators for high speed applications

The synthesis and performance evaluation of trilayer bending type polymer actuators in terms of frequency response and step response are described. The actuators are shown to achieve mechanical resonance at up to 90 Hz and giving tip displacements up to 60 mm for an input voltage of ±1 V at 4 Hz. Polypyrrole doped with trifluoromethanesulfonimide (TFSI) had a considerably higher speed of response when compared to polypyrrole-hexafluorophosphate (PF₆) actuator with the same dimensions. The TFSI doped polypyrrole showed faster charging rates, likely due to higher ion diffusion rates through a gel-like polymer structure, thereby producing faster actuation response. These new actuators may be useful for applications requiring a high speed of response, e.g. a propulsion element for a swimming device/robotic fish.     

Enhanced photovoltaic performance in inverted polymer solar cells using Li ion doped ZnO cathode buffer layer

We have proposed an approach to improve the photovoltaic performance of inverted polymer solar cells (i-PSC) using lithium ion doped ZnO (LiZnO) as cathode buffer layer (CBL). The LiZnO CBL was prepared using the diffusion technique, performed by inducing the Li ion of 8-hydroxyquinolatolithium (Liq) to diffuse into ZnO film through annealing the bi-layer ZnO/Liq film. Doping concentration of Li ion was controlled by using various thickness of Liq film and annealing temperature. Based on LiZnO CBL, the poly (3-hexylthiophene) [6,6]:-phenyl C61-butyric acid methyl ester (P3HT:PCBM) i-PSC device possessed a optimal power conversion efficiency (PCE) of 4.07%, which was 30% improved than that of the device with neat ZnO as CBL. The enhancement of the device performance could be attributed to the enhanced electron mobility and better band matching of the LiZnO CBL. Our finding indicates that the LiZnO film fabricated with relatively low temperature treatment has great potential for high-performance i-PSCs.     

Ultralow Threshold Red Vertical-Cavity Surface-Emitting Lasers

Visible Vertical-cavity Surface-emitting Lasers (VCSELs) have been designed and fabricated by using metalorganic vapor phase epitaxy. Using the 8λ optical cavities with 3 quan tum wells in A1GaInP/AlGaAs VCSEL's to reduce the drift leakage current and enhance the model gain, the device can operate continuous wave at wavelength of 670nm. For better performance, a misoriented (100) substrate (6～10° to (110)) has been used to reduce the ordering of AlGaInP. However, as the angle of misorientation increased, the symmetry of the structure became worse. This made it difficult to achieve little aperture device. By using 45° rotated selective oxidation method, a little aperture (1 × 1μm2) device with low threshold of 0.25mA can operate continuous wave at room temperature.     

Arrayed-Waveguide Layout for AWG Design

The key issue of the complex geometry for arrayed-waveguide grating(AWG)is the design of length difference.Conventional-type scheme and improved-type scheme of the ar-rayed -waveguide layout are proposed.For each scheme,the layout rules were given and one ex-ample was presented. At last ,the two schemes were compared with each other.     

10 Gb/s电吸收调制器的微波封装设计

在高速光电子器件的微波封装过程中，需要综合考虑封装寄生参数和芯片寄生参数对器件高频性能的影响。利用封装寄生参数对芯片寄生参数的补偿作用，成功实现了10Gb／s电吸收调制激光器（EML）的高频封装。通过封装前后芯片和器件的小信号频率响应测试结果对比，器件的反射参数和传输参数有所改善，3dB带宽达到10GHz；并进行了10Gb／s速率的光纤传输实验，经过40km光纤传输后通道代价不到1dBm（误码率为10^-12），满足10Gb／s长距离光纤传输系统的要求。     

Current-induced butterfly shaped domains and magnetization switching in magnetic tunnel junctions

Patterned magnetic tunnel junctions (MTJs) with the layer structure of Ta (5 nm)/Ni₇₉Fe₂₁ (5 nm)/Cu (20 nm)/Ni₇₉Fe₂₁ (5 nm)/Ir₂₂Mn₇₈ (10 nm)/Co₇₅Fe₂₅ (4 nm)/Al (0.8 nm)-oxide/Co₇₅Fe₂₅ (4 nm)/Ni₇₉Fe₂₁ (20 nm)/Ta (5 nm) were fabricated using magnetron sputtering deposition and lithography. High tunnelling magnetoresistance ratios of 22 and 50% were obtained at room temperature before and after annealing, respectively. The evolution of leaf shaped images was observed via Lorentz transmission electron microscopy (LTEM) on the MTJs, which were deposited on a patterned and carbon-coated transmission electron microscopy grid. These leaf-like LTEM images correspond to a butterfly shaped domain structure that was confirmed by a micromagnetics simulation. When a large DC current or bias voltage was applied across the MTJ, the butterfly-like vortex domain structures could be induced to form in the free layer of the MTJ, resulting in a significant decrease of magnetization in the free layer. The existence of these butterfly shaped domains could be one of the major causes of the bias voltage dependence of the TMR ratio.     

Effects of Growth Conditions on Optical Properties of GaInNAs/GaAs Quantum Well Grown by Molecular Beam Epitaxy

During the process of molecular beam epitaxy employing a DC plasma as N source,the effects of the growth temperature, growth rate and As4 pressure on the optical properties of GaInNAs Quantum Well(QW) are similar to those of InGaAs QW with the same In contents.In the range of 400 to 470℃, elevating growth temperature is beneficial to the improvement in the photoluminescence (PL) peak intensity of GaInNAs QW, but obviously broadens the fullwidth at half maximum PL peak. The improvement of optical properties and the reduction of N incorporation have been observed by increasing the growth rate. As4 pressure mainly affects the optical properties of GaInNAs QW rather than N incorporation does.     

SOI-Based 3dB MMI Splitter

A type of SOI-based MMI 3dB splitter has been demonstrated. The geometry was analyzed and designed by effective index method and guide mode method. The fabrication tolerance was analyzed too. The device was fabricated and near-field output was obtained. The device shows large width tolerance, low loss and low power uniformity.     

带胶剥离工艺粘附性实验研究

带胶剥离是微电子工艺的常见工艺步骤.文章通过对带胶剥离的样品进行退火实验,研究了电极蒸发金属和不同基底的粘附特性.实验表明,带胶剥离工艺制备的电极,其金属与衬底的粘附性差,退火过程产生气泡,严重影响了器件的特性.蒸发温度、蒸发室真空度,以及基片表面的清洁度与气泡产生有密切的关系.从这几点入手,提出了相应的改进方法.