Author Affiliations
Abstract
Department of Physics, Northwest University of China, Xi'an 710069, China
A metal bellows-based fiber Bragg grating (FBG) accelerometer is proposed and experimentally demonstrated. The optical fiber (containing the FBG) is pre-tensioned, and the two ends of the optical fiber are fixed directly from the shell to the inertial mass. In this design, the FBG is uniformly tensioned to obtain a constant strain distribution over it. By employing this configuration, the FBG always has a sharp reflection characteristic with no broadening in its reflection spectrum during wavelength shifting. Dynamic vibration measurements show that the proposed FBG accelerometer has a wide frequency response range (5–110 Hz) and an extremely high sensitivity (548.7 pm/g). The two important indicators of FBG accelerometer can be tuned by the addition of mass to tailor the sensor performance to specific applications, identifying it as a good candidate for structural health monitoring.
光纤光栅 金属波纹管 加速度传感器 060.2370 Fiber optics sensors 230.1480 Bragg reflectors 050.2770 Gratings Chinese Optics Letters
2011, 9(9): 090606
Author Affiliations
Abstract
Department of Physics, Northwest University of China, Xi'an 710069, China
The intelligent structural health monitoring method, which uses a fiber Bragg grating (FBG) sensor, is a new approach in the field of civil engineering. However, it lacks a reliable FBG-based accelerometer for taking structural low frequency vibration measurements. In this letter, a flextensional FBG-based accelerometer is proposed and demonstrated. The experimental results indicate that the natural frequency of the developed accelerometer is 16.7 Hz, with a high sensitivity of 410.7 pm/g. In addition, it has a broad and flat response over low frequencies ranging from 1 to 10 Hz. The natural frequency and sensitivity of the accelerometer can be tuned by adding mass to tailor the sensor performance to specific applications. Experimental results are presented to demonstrate the good performance of the proposed FBG-based accelerometer. These results show that the proposed accelerometer is satisfactory for low frequency vibration measurements.
光纤光栅 加速度计 弯曲伸张弹性结构 低频振动 060.2370 Fiber optics sensors 230.1480 Bragg reflectors 050.2770 Gratings Chinese Optics Letters
2011, 9(9): 090607
1 西北大学物理学系, 陕西 西安 710069
2 榆林学院物理与电气工程系, 陕西 榆林 719000
3 西北大学光子学与光子技术研究所暨陕西省光电子省级重点开放实验室, 陕西 西安 710069
4 西北大学信息科学与技术学院, 陕西 西安 710069
研制一台激光二极管(LD)侧面抽运双棒串接准连续Nd∶YAG折叠腔高功率绿光激光器,理论分析了热致双折射效应对系统的影响,并对用石英旋转片补偿前后的情况进行模拟对比。在考虑了补偿后的情况下设计了热稳定谐振腔。实验中采用两个串接的由30个20 W的LD阵列侧面抽运的Nd∶YAG棒和Ⅱ类临界相位匹配HGTR-KTP晶体,在抽运电流均为21.6 A,重复频率为27.2 kHz时,获得了最大平均输出功率为164 W,脉冲宽度为130 ns的532 nm绿光输出,光-光转换效率为13.7%,测得光束质量因子为M2x=9.52, M2y=9.86,不稳定度为2.3％。实验结果显示,经补偿后的激光系统能在宽的稳区范围内稳定运转。
激光器 高功率 热致双折射效应 532 nm绿光
为扩大数字全息的测量视场,使数字全息可以应用于大物体三维形貌的测量,利用菲涅耳离轴数字全息,让照明光依次照明物体的各个区域并分别记录全息图,利用精密电控旋转台精确控制参考光的入射角以保证每次记录时物参角不变,通过参考光入射角的变化量确定物体不同被照明区域之间的位置关系,对获得的物体去包裹的相位图进行拼接,进而得到整个物体的三维形貌。利用该方法测量了大小为11 cm×19 cm的石膏嘴的三维形貌,图像拼接的绝对拼接误差远小于1.14 mm,高度测量误差约为0.5 mm,实验结果说明这种测量方法能够有效地扩大数字全息测量物体三维形貌的视场并且具有和横向分辨率相当的拼接精度。
信息光学 形貌测量 数字全息 图像拼接 视场
1 西北大学物理系,西安,710069
2 中国科技大学物理系,合肥,230046
研究了偶氮共聚聚合物的光致双折射特性,利用幂指数和高斯函数拟合双折射过程中不同的物理过程,对各种不同的浓度、泵浦功率、主链运动及实验温度对双折射特性的影响进行了讨论,并在光致双折射过程中对样品的饱和回落进行了观察和分析,随着样品浓度的增加,尽管双折射的绝对值增大,但残留比例减小.
光致双折射 偶氮笨 共聚物 饱和回落
1 中国科技大学物理系,合肥,230026
2 西北大学物理系,西安,710069
3 中国科学院安徽光学精密机械研究所三室,合肥,230031
利用外周期信号对处于周期态的声光双稳态系统进行驱动,在合适的驱动强度和频率下,系统可能从周期态转换为李雅普诺夫指数意义下的混沌态.提出了这一混沌反控制方法,针对声光双稳态系统进行了计算模拟,并分析了其机理.
声光双稳态系统 混沌反控制 周期驱动 李雅普诺夫指数
用射频直流磁控溅射法在硅、石英基片上制备碳氮膜;采用傅里叶变换红外光谱(FTIR)技术,对基片上的碳氮膜进行红外光吸收谱测量,发现所制备的膜中有β相的C3N4;用硬度计测量镀膜后的硬度,均比镀膜前有所增强;对所制备的膜进行热处理,结果发现热处理前膜的红外吸收谱与热处理后的红外吸收谱相比没有变化,说明膜的热稳定性较好,可以作为红外光学材料.
碳氮膜 磁控溅射 红外光吸收谱
研究了激光辐照下约瑟夫森结的直流I-V特性变化,并对Ⅰ-Ⅴ曲线下移的实验结果进行了分析,认为是光拆库柏对效应所致.该结果为发展一种新的可见光探测器提供了思路.
激光辐照 库柏对 约瑟夫森结
