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991.
提出并研制了一种结构简单、成本低廉的温度与应变同时测量系统,其结构是在保偏光纤Sagnac环内接入一个长周期光纤光栅(LPFG)。利用LPFG对保偏光纤Sagnac环的透射光谱进行调制,通过监测谐振峰波长和强度的变化,发现波长随温度和保偏光纤的应变变化,强度随LPFG的应变变化,因此可以实现温度与应变的区分测量,并且可判断出应变的施加位置。实验得到该系统的温度灵敏度为0.181 81 nm·℃-1,LPFG区的应变灵敏度为0.005 283 dB·με-1,保偏光纤Sagnac环区的应变灵敏度为0.015 72 nm·με-1。实验结果表明该方案可行,并具有一定的实用性。 相似文献
992.
We present a method to optimize the Coupling efficiency between two fibers using a Holographic Coupler taking diffraction
effect into account. For this we obtain expressions for field distributions at the end facet of a fiber. The results obtained
by using the expression is found to be in good agreement with the finite element method in literature, the small deviation
is attributed to the negligence of field in the cladding. We then use the Kogelnik theory to obtain useful formulae suitable
for diffracted optical elements. The diffraction efficiency expressions are then used to predict the different parameters
of Holograting so as to get maximum diffraction efficiency in a direction where the field distribution from the end facet
is minimum thereby increasing the coupling efficiency.
相似文献
993.
Samuel Alan McDonald Federica Marone Christoph Hintermüller Gordan Mikuljan Christian David Franz Pfeiffer Marco Stampanoni 《Journal of synchrotron radiation》2009,16(4):562-572
Phase‐sensitive X‐ray imaging methods can provide substantially increased contrast over conventional absorption‐based imaging, and therefore new and otherwise inaccessible information. Differential phase‐contrast (DPC) imaging, which uses a grating interferometer and a phase‐stepping technique, has been integrated into TOMCAT, a beamline dedicated to tomographic microscopy and coherent radiology experiments at the Swiss Light Source. Developments have been made focusing on the fast acquisition and post‐processing of data to enable a high‐throughput of samples, with obvious advantages, also through increasing the efficiency of the detecting system, of helping to reduce radiation dose imparted to the sample. A novel aquarium design allows a vertical rotation axis below the sample with measurements performed in aqueous environment. Optimization of the data acquisition procedure enables a full phase volume (1024 × 1024 pixels × 1000 projections × 9 phase steps, i.e. 9000 projections in total) to be acquired in 20 min (with a pixel size of 7.4 µm), and the subsequent post‐processing has been integrated into the beamline pipeline for sinogram generation. Local DPC tomography allows one to focus with higher magnification on a particular region of interest of a sample without the presence of local tomography reconstruction artifacts. Furthermore, `widefield' imaging is shown for DPC scans for the first time, enabling the field of view of the imaging system to be doubled for samples that are larger than the magnification allows. A case study is illustrated focusing on the visualization of soft tissue features, and particularly the substantia nigra of a rat brain. Darkfield images, based on local X‐ray scattering, can also be extracted from a grating‐based DPC scan: an example of the advantages of darkfield contrast is shown and the potential of darkfield X‐ray tomography is discussed. 相似文献
994.
Chun-Liu Zhao Jiarong Zhao Wei Jin Jian Ju L. Cheng Xuguang Huang 《Optics Communications》2009,282(20):4077-4080
We present a new design for simultaneous strain and temperature measurement using a high-birefringence fiber loop mirror (HiBi-FLM) concatenated with a temperature-insensitive long-period grating (LPG) written in a photonic crystal fiber (PCF). The FLM acts as a sensor head, while the LPG in PCF serves as a filter to convert wavelength variation to optical power change. By measuring the wavelength variation and the power difference of two near peaks in the spectral response of this configuration, simultaneous strain and temperature measurement is obtained. 相似文献
995.
Suchun Feng Ou Xu Shaohua Lu Tigang Ning Shuisheng Jian 《Optics Communications》2009,282(11):2165-4916
Switchable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser based on one polarization-maintaining fiber Bragg grating (PMFBG) is demonstrated. Due to the enhancement of the polarization hole burning (PHB) by the PMFBG, the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). The stable SLM operation is guaranteed by a compound-ring cavity and a saturable absorber (SA). The optical signal-to-noise ratio (OSNR) is over 45 dB. The amplitude variation in nearly one and half an hour is less than 0.2 dB. 相似文献
996.
A stable dual-wavelength erbium-doped fiber laser with a linear cavity is formed by a polarization-maintaining uniform fiber Bragg grating (PM-FBG) and a polarization-maintaining linearly chirped fiber Bragg grating (PM-LCFBG), both of which were fabricated on a high-birefringence (Hi-Bi) fiber. Experimental results show stable dual-wavelength lasing operation with a wavelength separation of ∼0.22 nm, which can be tuned down to as small as 0.05 nm and a large optical signal-to-noise ratio (OSNR) of over 40 dB under room-temperature. Microwave signal at frequency of 9.41, 18.03 and 27.46 GHz is achieved by heterodyned the output lasing wavelengths on a photodetector. 相似文献
997.
998.
声光Naman-Nath衍射特性的研究 总被引:3,自引:1,他引:2
讨论了液体介质中的超声相位光栅的形成,根据声光相互作用类型的区分标准,在液体介质的超声光栅实验中声光相互作用一般为Naman-Nath衍射;相位光栅可以由声行波和声驻波形成,且形成的各级衍射条纹极大均由相同的光栅方程决定,各级衍射条纹的强度由相应阶次的J2m函数值决定;在此基础上给出了衍射条纹和衍射光强的分布特点. 相似文献
999.
1000.
针对利用液晶空间光调制器(LC-SLM)进行全息图光电再现过程中,再现像面存在多级衍射像造成单一像能量利用率低的问题,提出了一种在位相全息图中加载数字闪耀光栅的方法,以提高全息图光电再现中单一衍射像的衍射效率.分析了闪耀光栅作为衍射光学元件的特性及其对光波进行位相调制的原理,并阐述了在LC-SLM中加载数字闪耀光栅对位相全息图光电再现时像面能量分布的影响.搭建了基于LC-SLM的位相全息图光电再现实验系统.理论分析表明:在其他条件不变的情况下,加载竖直(或水平)槽向周期为2 pixels的数字闪耀光栅可使
关键词:
全息光电再现
位相全息图
数字闪耀光栅
液晶空间光调制器 相似文献