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1.
A hexagonal ordered structure of magnetic columns, which results from an agglomeration of magnetic particles, is obtained in a magnetic fluid film when a magnetic field is applied perpendicularly to the film surface. The evolution of the initially ordered structure in the magnetic fluid film during the heating and cooling process is investigated under a given magnetic field. For the heating process, the columns remain unchanged until the temperature exceeds a critical temperature. As the temperature is further increased, column particles start to disperse into the liquid carrier. As a result, portions of columns disappear. As the temperature continue to rise, the ordered structure changes to a disordered column state, or even a monodispersed state. On the other hand, when the temperature is lowered, the magnetic particles in the carrier condense out of solution and finally an ordered structure of columns is achieved. However, this structural evolution during a thermal cycle is irreversible.Received: 28 August 2004, Published online: 21 October 2004PACS:
75.50.Mm Magnetic liquids - 64.75. + g Solubility, segregation, and mixing; phase separation - 68.60.Dv Thermal stability; thermal effects 相似文献
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Huang YW Hu ST Yang SY Horng HE Hung JC Hong CY Yang HC Chao CH Lin CF 《Optics letters》2004,29(16):1867-1869
When an external magnetic field is applied parallel to the film surface of a magnetic fluid film, a high-quality one-dimensional periodic chain structure is formed when the field strength reaches a certain level. With a periodic chain structure in the magnetic fluid film, an incident light is diffracted onto the magnetic thin film. The results show that the one-dimensional periodic chain structure in the magnetic fluid film can serve as an optical grating. Further investigations reveal the feasibility of developing tunable coarse wavelength-division multiplexing by utilizing a periodic chain structure. 相似文献
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Magneto-optical fiber sensor based on magnetic fluid 总被引:2,自引:0,他引:2
A novel magnetic field fiber sensor based on magnetic fluid is proposed. The sensor is configured as a Sagnac interferometer structure with a magnetic fluid film and a section of polarization maintaining fiber inserted into the fiber loop to produce a sinusoidal interference spectrum for measurement. The output interference spectrum is shifted as the change of the applied magnetic field strength with a sensitivity of 16.7 pm/Oe and a resolution of 0.60 Oe. The output optical power is varied with the change of the applied magnetic field strength with a sensitivity of 0.3998 dB/Oe. 相似文献
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多孔氧化铝薄膜的制备和光学特性研究 总被引:5,自引:2,他引:3
采用阳极氧化法制备了二维有序纳米孔氧化铝膜.研究了工艺参数对多孔薄膜有序性、孔径、膜厚度等的影响,测量了多孔氧化铝有序膜的光透过、光吸收和光发射等光学特性.结果表明,在波长360 nm附近多孔氧化铝有序膜的光透过谱线和光吸收谱线发生突变,波长大于360 nm时,光透过增强;波长小于360 nm时,光吸收增强.多孔氧化铝有序膜的光致发光强度和峰位与激发光波长有关,光致发光谱范围在340~600 nm. 相似文献
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采用二步阳极氧化法在草酸溶液中制备了多孔阳极氧化铝(PAA)薄膜。借助于扫描电子显微镜(SEM)分析了多孔阳极氧化铝薄膜的微观形貌。结果发现,在其表面孔径为30~40nm的六边形孔洞分布均匀,且垂直于表面平行生长。依据PAA透射光谱的实验数据,采用极值包络线算法计算出了PAA薄膜的复折射率以及光学能隙等光学常数。通过分析吸收系数与入射光子能量之间的关系发现,PAA薄膜具有直接带隙半导体的电子结构特征,而且由理论计算得到的PAA的带隙能与其光致发光谱的峰位能是一致的。 相似文献
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Y. Zhang X.Y. Dang J. Jin T. Yu B.Z. Li Q. He F.Y. Li Y. Sun 《Applied Surface Science》2010,256(22):6871-6875
In this combined film thickness, scanning electron microscopy (SEM), X-ray diffraction and optical properties study, we explore the effects of different stirring speeds on the growth and optical properties of ZnS film deposited by CBD method. From the disclosed changes of thickness of ZnS film, we conclude that film thickness is independent of the stirring speeds in the heterogeneous process (deposition time less than 40 min), but increases with the stirring speeds and/or deposition time increasing in the homogeneous process. Grazing incident X-ray diffraction (GIXRD) and the study of optical properties disclosed that the ZnS films grown with different stirring speeds show partially crystallized film and exhibit good transmittance (70-88% in the visible region), but the stirring speeds cannot give much effects on the structure and optical properties in the homogeneous process. 相似文献
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Guo Peitao Xia Zhilin Xue YiyuHuang Caihua Zhao Lixin 《Applied Surface Science》2011,257(8):3307-3312
The porous optical film has higher threshold of laser-induced damage than densified films, for the study of mechanism of laser-induced damage of porous optical film with ordered pore structure. Porous anodic alumina (PAA) film with high transmittance on glass substrate has been prepared. Aluminum film was deposited on glass substrate by means of resistance and electron beam heat (EBH) evaporation. Porous alumina was prepared in oxalic acid solution under different anodizing conditions. At normal incidence, the optical transmittance spectrum over 300-1000 nm spectra region was obtained by spectrophotometer. SEM was introduced to analysis the morphology of the porous alumina film. The pore aperture increased with the increase of anodizing voltage, which resulted in a rapid decrease of the pore concentration and the optical thickness of porous alumina film. Damage morphology of porous alumina film is found to be typically defects initiated, and the defect is the pore presented on the film. 相似文献
11.
Ying Wang Baojun Ding Hua Li Xiaoyan Zhang Bingchu Cai Yafei Zhang 《Journal of magnetism and magnetic materials》2007
The monolayer of FePt nanoparticles with the mean size of ∼4 nm was fabricated on a glass substrate by the Langmuir––Blodgett (LB) technology. The monolayer of FePt nanoparticles has a smooth surface and a high density structure as shown by the AFM image. The array structure of FePt nanoparticles on the surface of the film is clearly with a cubic symmetry in appropriate condition. Small-angle X-ray diffraction (SXRD) measurement of multilayer structure for the FePt nanoparticles has indicated that the superlattices consist of well-defined smooth layers. The transfer of nanoparticle layers onto a solid substrate surface was quite efficient for the first few layers, exhibiting a proportional increase of optical absorption in the UV–vis range. This results potentially opens up a new approach to the long-range ordered array of FePt nanoparticles capped by organic molecules on substrate and provide a promising thin film, which may exhibit the excellent ultra-high density magnetic recording properties. 相似文献
12.
A fiber optic integrated modulation-depth-tunable modulator based on a type of hollow optical fiber with suspended core is proposed and investigated. We synthesized magnetic fluid containing superparamagnetic Fe(3)O(4) nanoparticles and encapsulated it in the hollow optical fiber as the cladding layer of the suspended core by fusing the hollow optical fiber with the multimode optical fibers. The light with a wavelength of 632.8 nm is coupled in and out of the modulating element by a tapering technique. Experimental results show that the light attenuation in the system can be greatly influenced by only 2.0×10(-2) μL of the magnetic fluid under different magnetic field strengths. The saturated modulation depth is 43% when the magnetic field strength is 489 Oe. The response time of the system is <120 ms. Significantly, this work presents information for the development of all-fiber modulators, including other integrated electro-optic devices, such as optical switch, optical fiber filter, and magnetic sensors utilizing the special structure of this hollow optical fiber with suspended core and superparamagnetic magnetic fluid. 相似文献
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A magneto-optic modulator with a magnetic fluid film inserted into an optical fiber Sagnac interferometer is proposed. The magnetic fluid exhibits variable birefringence and Faraday effect under external magnetic field that will lead to a phase difference and polarization state rotation in the Sagnac interferometer. As a result, the intensity of the output light is modulated under the external magnetic field. Moreover, the modulator has a high extinction ratio and can easily be integrated in a single-mode fiber system. The performance of the modulator is not affected by ambient temperature variation from room temperature to 40 °C. 相似文献
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A magnetic field induced agglomeration of magnetic and μm-sized copper non-magnetic particles in magnetic fluid with several
volume concentrations of magnetite and copper particles was studied by means of optical microscope equipped with video camera.
Transmission of light through two crossed polarizers and thin magnetic fluid and magnetic fluid composites film as a function
of magnetic field was investigated. The experimental data showed that the presence of copper particles influences the aggregation
processes of magnetic particles in magnetic fluids and transmissivity of light.
Dedicated to Dr. Anton Zentko on the occasion of his 60th birthday.
This work was supported by the Slovak Academy of Sciences within the framework of Project GAV No. 4001. 相似文献
15.
Tunable magnetoben-optic modulation based on magnetically responsive nanostructured magnetic fluid
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Magnetic fluid is a kind of functional composite material with nanosized structure and unique optical properties. The tunable magneto-optic modulation of magnetic fluid under external magnetic field, achieved by adjusting the polarization direction of incident light, is investigated theoretically and experimentally in this work. The corresponding modulation depth and response time are obtained. The accompanying mechanisms are clarified by using the theory of dichroism of magnetic fluid and the aggregation/disintegration processes of magnetic particles within magnetic fluid when the external magnetic field turns on/off. 相似文献
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Abstract An extrinsic Fabry–Perot optical fiber sensor based on nano-magnetic fluid and a Fabry–Perot interference is presented for magnetic field measurement. The sensing fiber end is coated with a thin film of SU-8 photoresist; immersing it into a nano-magnetic fluid forms a magnetic-field-dependent extrinsic Fabry–Perot interference. The relationship between the fringe contrast and magnetic field is analyzed in different concentrations of the magnetic fluid, and the concentration of 25% is most suitable for the measurement of the magnetic field intensity. The stability of the sensor is also addressed. 相似文献
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In this paper, optical limiting property in a magnetic fluid film is studied. The relationship between the emergent power and the incident power is investigated experimentally and theoretically. It is found that the limiting threshold is linear with the diaphragm aperture which accord with the theoretical prediction. The external magnetic field will affect the limiting property, and increase the limiting threshold. 相似文献
19.
Laser-illuminated atoms in an optical resonator exhibit a phase transition between the homogenous distribution and two possible ordered configurations in the optical lattice formed by the cavity and pump fields. At zero temperature, atom-field entanglement plays a crucial role in the spatial reordering of the atoms from a homogeneous towards the two ordered states, where all atoms occupy either only even or only odd lattice sites. Concurrent with the buildup of atom-field entanglement, the homogeneous atomic cloud evolves immediately into the superposition of the two stable patterns entangled with opposite cavity field amplitudes. This possibility is absent in a factorized (classical) treatment of atoms and field and should be generic for spontaneous symmetry breaking in quantum phase transitions in optical potentials. 相似文献
20.
S. V. Stebnovskii 《Technical Physics》2002,47(11):1369-1372
It is experimentally found that homogeneous polar fluids (water, glycerol, ethanol, etc.) become optically anisotropic under shear. As a result, the permittivity, which is a macroscopic characteristic of a fluid, becomes anisotropic as well. Results obtained indicate that quiescent polar fluids have signs of an ordered structure, which readily disappears under weak shear stresses and then relaxes to the initial state for several hours (depending on the fluid temperature). 相似文献