Surface Plasmon-polaritons on an Anisotropic Substrate

Abstract

The case of a surface plasmon-polariton (excited by transverse magnetic light) propagating at the interface between an isotropic metal (silver) and an anisotropic (uniaxial) substrate is considered. The field distribution within the system is illustrated when the optic axis of the substrate is not orthogonal in the plane of light propagation. It is seen that in this case a component of the electric field perpendicular to the plane of propagation exists, and in certain circumstances this can become a propagating transverse electric mode. Thus a transverse electric re-radiation occurs, which is enhanced by the surface plasmon resonance, this could form the basis of an electro-optic switch using the anisotropic properties of a liquid crystal layer.     

Infrared Surface Plasmon-polaritons on Ni,Pd and Pt

Abstract

Surface plasmon-polaritons (SPP) have been excited on evaporated films of the transition metals nickel, palladium and platinum. Using the Otto geometry and a He/Ne laser operating at 3·391 μm we report the first characterisations of these metals using this technique. Adjusting the air-gap over the range 4 to 15 μm has allowed observation of > 95% coupling of p-polarised (TM) radiation to the SPP and precise quantification of the optical dielectric constants of the metal films. The relatively large imaginary components so obtained mean that these materials may not readily be used in the Kretschmann geometry at this wavelength. By contrast the SPP resonances observed using the Otto geometry are sharp and open up potential for catalytic studies with SPP excitation on these metals.     

超材料对电磁波的极化转换及不对称传输研究进展

超材料新颖的电磁特性使它在许多领域都具有潜在的应用价值,如极化旋转器、类二极管等光子器件。综述了超材料中电磁波的极化转换的研究进展,包括线极化波之间、线极化波和圆极化波之间、圆极化波之间的相互极化转换,以及超材料的线极化波和圆极化波的不对称传输,并阐明了利用类Fabry-Perot谐振腔增强线极化波和圆极化波的不对称传输效应的机制。     

Prism-coupled excitation of multiple Tamm waves

Abstract

A Tamm wave is guided by the interface of a homogeneous dielectric material and a periodically nonhomogeneous dielectric material, both isotropic. We found theoretically that multiple Tamm waves of different linear polarization states can be guided by such an interface incorporated in a prism-coupled configuration. The Tamm waves have different linear polarization states, phase speeds, and spatial profiles, but the same frequency. The narrow absorptance peaks associated with the excitation of Tamm waves in the prism-coupled configuration offer the application as chemical sensors with very high sensitivity.     

Quantum Cryptography Using Polarization Feedback

Abstract

A system for quantum cryptography using polarization-preserving optical fibre and a feedback loop to compensate for time-dependent changes in the state of polarization has been implemented. Error rates of less than 0·5% have been demonstrated and much lower error rates can be expected in the future. An improved system that does not require the use of polarization-preserving fibre, and with expected data transmission rates of 100 kHz, is under construction.     

On the Properties of Surface Plasmon Polarization Beam Splitters

Abstract

The transmission and cross-coupling characteristics of a surface-plasmon-based polarization beam splitter with multimode interlay between two polished optical fibre blocks are presented. Through the continuous monitoring of the characteristics as a function of interlay refractive index and wavelength it was found that the device is symmetrical in terms of optical power coupling in the cross direction and asymmetrical in terms of transmission, with respect to input launch direction. The fibre fixed in the metal-coated block has a transverse electric (TE) mode transmission which is independent of the refractive index of interlay. The transmission of the other (uncovered) block shows resonance-type interaction for both TE and transverse magnetic modes owing to evanescent field coupling to the multimode interlay.     

Phase Shifting Scatter Plate Interferometer Using a Polarization Technique

Abstract

The structure of a conventional scatter plate interferometer is modified by a polarization technique, and a new type of phase shifting scatter plate interferometer is presented. It has both the merits of a conventional scatter plate interferometer and the phase shifting interferometric technique. The working of this interferometer is demonstrated.     

利用挤压光纤双折射效应的自适应偏振控制器

报导了利用光纤应力双折射效应研制的1．55μm波长的自适应偏振控制 器,该控制器具有自动搜索、跟踪和精确控制光纤输出偏振态的功能。经初步检测,当偏振态变化3π/s时,输出偏振光强度为给定偏振方向分量总光强的92％,平均偏差小于2％。     

采用偏振分光棱镜的光桥式补偿技术

介绍了一种使用偏振分光棱镜的新型光桥式补偿技术。研究了棱镜消光比变化引起的误差。使用该补偿结构的光纤压力传感器已实际应用于石油化工部门油罐储量计量，其现场运行长期稳定性优于０．２％。     

成膜时间对镁合金铈盐转化膜的影响

以往鲜见成膜时间对稀土转化膜影响的系统研究。以优化后的转化工艺0.02 mol/L铈盐,5 mL/LH2O2,温度30℃,pH=2,在镁合金表面制得稀土转化膜,通过对不同转化时间制得的膜进行表面形貌分析、能谱分析、浸泡腐蚀试验和电化学试验,考察膜的形成过程及耐腐蚀性能。结果表明:随转化时间的延长,耐蚀性呈现增强的趋势;转化膜是在2种不同推动力下形成的双层膜结构,双层膜的耐腐蚀能力也不同;减少裂纹和修补裂纹是提高膜耐腐蚀能力的必要措施。     

铝合金表面铈基转化膜研究进展

铝合金具有成本低、强度质量比高、可加工性能良好等优点,被广泛应用于航空、交通、建筑等领域.但铝合金表面易发生小孔腐蚀和晶间腐蚀,需要进行防腐处理才能满足应用要求.稀土元素铈因具有特有的电子层结构和物理化学特性,是制备铝合金稀土转化膜最具优越性的元素,以此为防腐基材开发的稀土转化膜技术被认为是最有可能替代铬酸盐钝化的技术.目前所报道的铈基转化膜工艺有化学浸泡法、溶胶-凝胶法、电化学法、磁控溅射法等.其中,化学浸泡法制备过程简单,但铈离子的转化和沉积速率较难控制一致,膜层微米级裂纹较多;溶胶-凝胶法制备的膜层与基体结合强度高,耐蚀性好,但需要大量铈盐,且产生较多废酸、碱液,成本高,环境污染大;电化学法在低温下实现性能可控的铈基转化膜,成本低,但成膜有大量晶间裂纹,结构疏松,成膜质量差;磁控溅射法制备的涂层均匀,成分可控,但靶材的利用率低,难以实现强磁性材料的低温高速溅射.总体来看,目前所报道的铈基转化膜工艺存在溶液体系稳定性差,所制备的转化膜层不稳定、容易开裂,以及制备成本较高的问题,难以满足工业化应用的要求.铈基转化膜成膜机理被普遍认为是阴极成膜理论,即铝合金表面形成了氧化还原微电池.溶液中的溶解氧以及加入的H2 O2可作为羟基的供体,通过改变溶液局部pH值、物质、电子和电荷浓度来影响稀土元素的氧化反应和在基体表面的沉积.铈基转化膜的耐蚀机理是阴极抑制机理,即在铝合金表面形成的铈基转化膜阻止了氧的传输和电子的转移和传递,从而阻止了阴极微区上的还原反应,防止了铝合金表面的腐蚀溶解.但该机制只强调了阴极抑制,而忽略了也可能发生的阳极抑制.同时,由于涉及到电化学动力学抑制,因此铈基转化膜有"自愈能力".本文综述了国内外铝合金铈基转化膜制备工艺的研究进展,指出了各工艺的优点和缺点,阐述了铈基转化膜主流成膜和耐蚀理论的研究,并对制备工艺的改进方向及未来理论的研究方向进行了展望.     

High-Rate Optically Isolated Analog Multiplexer Using Amplitude-to-Width Conversion

The operating principle and the performances of a new type of isolated analog multiplexer are described. It has a maximum sampling rate of 80 kHz, 2.5-kV isolation, dc CMRR higher than 140 dB, linearity error lower than 0.6 percent, and thermal drift in the order of 100 ?V/°C. Each acquisition channel has a floating pulsewidth modulator driving an optoelectronic coupler. This last controls a generator which injects a reference current into the virtual ground of an integrator common to all the channels. The resulting output analog voltage is digitized by a fast ADC. The analog information through the optical couplers is carried by a pulse of fixed amplitude and variable width. This circumvents the linearity and stability limitations of optical isolators. The described multiplexer has been devoted to analog data logging in electricity generating plants. Its sampling rate and accuracy performances have been optimized in view of this particular application. The system is susceptible of a factor 10 increase in speed with a limited degradation of other characteristics.     

圆锥面作为辅助面求作球体切平面

球体切平面作图方法在工程图学中较少研究,论文就单球、双球和三球体公切平面(在各种约定条件下)的形成原理,空间走向、表达形式以及数量作了详尽地分析,提出了利用圆锥面作为辅助面求作球体切平面的方法。对单球、双球和三球切平面作图方法采用了一题两解的办法,并对两种作法进行比较和分析,从而得出正确的结论。