基于双M-Z干涉仪的光纤周界防护系统

基于光纤双Mach-Zehnder干涉仪(MZI)结构对周界防护系统进行了设计研究。通过对两路经过不同延时的相同信号进行互相关运算,实现了对振动入侵点的定位。提出了一种分段数据处理方法,有效地提高了定位稳定性及准确性。测试结果表明,该双Mach-Zehnder干涉仪周界防护系统可以实时对振动点进行定位,在传感光纤长度为2km、采样率为2MHz时定位精度优于200m,能够长时间连续稳定工作。     

Al掺杂对正极材料LiNi0.33-xMn0.33Co0.33AlxO2结构和电化学性能的影响

以柠檬酸为螯合剂利用快速湿化学法合成了具有α-NaFeO₂型层状结构的LiNi_0.33-xMn_0.33Co_0.33Al_xO₂(x=0.00,0.01,0.02, 0.04)正极材料,并通过X-射线衍射、充放电测试、循环伏安和交流阻抗对材料的结构和电化学性能进行了系统研究。XRD结果表明此方法合成的材料具有很好的层状结构且阳离子的混排度随着Al³⁺含量的增加而下降。电化学测试表明,LiNi_0.31Mn_0.33Co_0.33Al_0.02O₂具有很好的电化学性能和和循环性能,1C放电倍率下首次放电比容量达到176.9 mAh·g^-1,且Al³⁺的掺杂能有效提高电荷在电极界面间转移并抑制了在高压循环过程中电荷转移阻抗的增加。     

Tunable directional beaming assisted by asymmetrical SPP excitation in a subwavelength metallic double slit

We present a design for tunable directional beaming through a subwavelength metallic double slit surrounded by dielectric surface-relief gratings.On-axis and off-axis beaming can be switched by controlling the incident angle to asymmetrically excite surface plasmon polaritons(SPPs) that are subsequently coupled out to propagating beams by the two gratings on the left and the right sides of the double slit.Furthermore,the division of optical power into two off-axis beaming directions can be tuned smoothly by varying the incident angle while keeping the total power almost unchanged.The mechanism of this effect is analyzed theoretically and verified using rigorous numerical simulations.     

Femtosecond Bessel-beam-assisted high-aspect-ratio microgroove fabrication in fused silica

A simple and repeatable method to fabricate high-aspect-ratio(HAR) and high-quality microgrooves in silica is reported. The method consists of two steps:(1) formation of laser-modified regions by femtosecond Bessel beam irradiation, and(2) removing laser-modified regions through HF etching. Uniform, straight microgrooves can be fabricated and the highest aspect ratio that can be reached is ～52. The phenomenon is attributed to the uniform energy distribution in the long propagation distance, which leads to the long and uniform laser-modified regions and subsequent HF acid etching of laser-modified regions with high selectivity. This method will have potential applications in fabrication of HAR microgrooves in transparent materials.