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211.
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213.
In the present study the response of the fiber optic evanescent field absorption sensor has been analyzed experimentally. The dependence of evanescent absorbance on sample (dye) concentration has been found to be nonlinear, in contradiction to theoretical predictions. The amount of nonlinearity as well as evanescent absorbance has been found to depend on the pH of the sample. As the pH decreases, the amount of nonlinearity and evanescent absorbance decrease. It has been shown that the nonlinearity and high evanescent absorbance at high pH value occur because of the adsorption of the positively charged dye molecules on the surface of the silica core of the plastic-clad silica (PCS) fiber, which is generally used for the sensor. A linear response has been obtained at pH close to 2.0, at which the presence of a tremendous amount of H ions in the sample restricts the adsorption of the dye molecules. The following empirical relation has been found to fit the experimental data: gamma 1.1C 1.6(pH)32C 1 3, where gamma is the evanescent absorption coefficient and C is the concentration of the dye. The first term is due to the simple Beer's law while the second term is the contribution of the pH dependent dye adsorption. In addition, we have found that the increase in core diameter increases the contribution of adsorption. 相似文献
214.
Maryam I. Daneshvar Guillermo A. Casay Gabor Patonay Malgorzata Lipowska Lucjan Strekowski Lawrence Evans III Leila Tarazi Abraham George 《Journal of fluorescence》1996,6(2):69-75
The design and application of a fluorescent fiber-optic immunosensor (FFOI) are reported. The FFOI is utilized for the detection of antibody/antigen binding within the near-infrared (NIR) spectral region. The technique is developed through the combined use of fiber-optic, semiconductor laser-excitation, fluorescence detection, NIR dye, and immunochemical techniques. The antibody is immobilized on the FFOI and utilized as a recognition component for trace amounts of specific antigen. The FFOI is constructed to utilize an antibody sandwich technique. The assay involves the immobilization of the capture antibody on the sensing tip of the FFOI followed by the exposure of the immobilized sensing tip to the antigen. The antigen-coated FFOI is then introduced to a second antibody previously labeled with the NIR dye. Typical measurements are performed in about 15 min. A semiconductor laser provides the excitation (780 nm) of the immune complex. The resulting emission is detected by a silicon photodiode detector (820 nm). The intensity of the resulting fluorescence is directly proportional to the concentration of the antigen. The sensitivity of the analysis reaches 10 ng/ml and the response time is 10–15 min. 相似文献
215.
考虑到光场的振幅随时间分布的影响时,我们重新研究了光场与二能级原子相互作用的跃迁几率问题。在强光信号作用下,经过一定的数学代换后,上能级几率的求解可归结为类希尔方程求解;在弱光信号作用下,利用转动波近似(RWA),给出了二能级原子跃迁几率的解析表达式,并讨论了几种典型脉冲光场的分布。 相似文献
216.
M. R. Koblischka S. L. Huang K. Fossheim T. H. Johansen H. Bratsberg 《Physica C: Superconductivity and its Applications》1998,300(3-4):207-211
Flux distributions of partial-melting processed Bi2Sr2CaCu2O8+δ ceramics are obtained using magneto-optic imaging. In remanent states (μ0Ha=0 T), large amounts of trapped flux are observed along (Sr,Ca)2CuOy particles embedded in the Bi2Sr2CaCu2O8+δ matrix. Despite the relatively large size of these particles (up to 30 μm), the pinning effect is similar to that of Y2BaCuO5 particles in melt-processed YBa2Cu3O7−δ. Furthermore, we discuss how the pinning capability of non-superconducting particles of different sizes and densities will show up in magneto-optic images. 相似文献
217.
THILO GIPSER HUBERT A. JAGER LUTZ RAPP Swiss Federal Institute of Technology Communication Technology Laboratory ETH Zentrum Zurich Switzerland 《Fiber and Integrated Optics》1998,17(1):21-40
All-optical networks are a sound answer to the huge data traffic demand expected for the forthcoming information society. Interesting networking aspects are the broadcasting, scalability, and reconfiguration in an all-optical environment. These issues are addressed in the present article for an all-optical network called MATRIX, which is time slotted and uses packet switching. The architecture enables the all-optical interconnection of a large number of nodes with both a small number of wavelengths and wavelength continuity based on a consequent exploitation of wavelength-division multiplexing and space-division multiplexing (i.e., multiple fibers per cable are used). For an efficient use of the resources, each node is equipped with multiple transmitters and receivers, respectively. Two different broadcasting schemes are investigated. An analytical model is developed, and the corresponding simulation results are in good agreement. It is further shown how different networks of arbitrary size can be interconnected to larger all-optical network clusters, thereby providing scalability not only with respect to the number of nodes but also to the geographical extension. Finally, wavelength reassignments allow change of optical paths through the network in case of changing traffic patterns or network failures in order to best exploit the available network resources. The total number of possible configurations is determined by the theory of Latin Squares. 相似文献
218.
A novel NMR spectrometer is described that is uniquely versatile in its ability to accurately record broad lines by sweeping the superconducting magnetic field and to perform standard high resolution solid state NMR experiments. Broadline observation is illustrated by 27Al spectra from static samples. Such an instrument opens up many nuclei for serious study by NMR in the solid state for the first time. 相似文献
219.
O?uz??elikelEmail author ?zcan?Bazkir Mehmet?Kü?üko?lu Farhad?Samedov 《Optical and Quantum Electronics》2005,37(6):529-543
This paper covers the absolute spectral power responsivity calibration of spectralon-coated Integrating Sphere Radiometer (ISR) equipped with 3 mm diameter InGaAs photodiode to be used as a transfer standard in fiber optic power measurements against Electrical Substitution Cryogenic Radiometer (ESCR) in Optics Laboratory of National Metrology Institute (TUBITAK UME) of Turkey. The initial uncertainty arising from the use of the Electrically Calibrated Pyroelectric Radiometer (ECPR) as a transfer standard in radiometric scale is 0.5% (k=2), which particularly comes from irregularity in the surface homogeneity of ECPR. In order to eliminate the ECPR step as well as its initial uncertainty contribution in fiber optic power measurements, the calibration application herein was carried out. Moreover power stabilization measurements of DFB laser sources at both 1309.1 nm and 1549.0 nm, the beam size determinations, and spectral analyses of these laser sources as well as spatial and angular dependence of spectral responsivities of the ISR were presented in this paper. The total expanded uncertainties were calculated as 0.283% and 0.315% in the determination of absolute spectral power responsivities of the ISR for 1309.1 nm and 1549.0 nm wavelengths respectively (k=2). 相似文献
220.
Lepère M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(14):969-3258
In this paper, we present the different theoretical line profiles, which can be used to describe a shape of molecular transitions in dilute gases: the Voigt, Galatry, Rautian and speed dependence models. We discuss their limitations and their advantages, and present for illustration different comparisons of model results with experimental data obtained with several diode laser spectrometers suitable for precise line shape measurements. 相似文献