Metal/dielectric transmission interference filters with low reflectance. 1. Design

For many applications the high reflectance of conventional multilayer interference filters is undesirable. It is possible to design and construct interference filters in which the transmittance and reflectance are independently controlled and in which the reflectance is very low. However, to do this it is necessary to employ absorbing coating materials and, as a result, a reduction in the peak transmittance must be accepted. We describe three different methods for the design of such coatings. Examples are given of a number of bandpass filters, neutral density filters, cutoff filters, and of an xˉ(λ) tristimulus filter, all having a low reflectance. This reflectance is frequently 15 to 50 times lower than that of conventional filters.     

Long-wavelength cutoff filters of a new type

A method for the design of cutoff filters is proposed that is based on the use of light at nonnormal angles of incidence and on the use of coating materials with a large dispersion of the optical constants. The optical constants are presented of several films made from indium tin oxide-a material that satisfies this requirement. The filtering is due to absorption, critical angle effects, or both. The theory of this type of filter is described, and the calculated performance of two long-wavelength cutoff filters based on the use of indium tin oxide films is given. The angular performance and the producibility of one of these filters are examined. Some applications for these filters are considered, and the feasibility of producing similar filters for other spectral regions is discussed.     

Implementation of long-wavelength cut-off filters based on critical angle

Our first attempts at the fabrication of long-wavelength infrared cut-off filters with extended transmission and rejection regions that are based on the use of the critical angle, the dispersion of refractive indices, and on thin-film interference were not very successful. The design of the filter consisted of layers placed at the interface between two high-index prisms. Using the available deposition equipment, the layers produced were porous and very rough. The pores adsorbed water vapor, which resulted in absorption. The roughness made the process of optical contacting very difficult. In this paper we describe the adjustments in the design and deposition processes that allowed us to obtain filters with a better and more stable performance.     

Design considerations for narrow-band dielectric resonant grating reflection filters of finite length

An interference-waveguide approach is developed to predict the response of a resonant grating reflection filter and to provide a better understanding of the resonant process. An expression for the reflected field that accounts for all internal boundary reflections within the filter is developed. Under the assumption of an anti-reflective design, expressions characterizing the line shape of a filter of infinite length are first developed; then the effects of finite length on the response are determined. Expressions relating the length of the filter to the peak reflection efficiency and line width are developed. The degradation of the response as a function of filter length is evaluated. An equivalent waveguide representation is used to determine the location of the resonance as well as the spectral and angular linewidths of the filter. The minimum obtainable spectral linewidth for a filter of given length is determined to be on the order of deltalambda approximately lambda2/L. Rigorous analysis is used to verify the interference-waveguide approach.     

Dielectric/metal/dielectric structures using copper as metal and MoO3 as dielectric for use as transparent electrode

Transparent conductive oxide/metal/oxide, where the oxide is MoO₃ and the metal is Cu, is realized and characterized. The films are deposited by simple joule effect. It is shown that relatively thick Cu films are necessary for achieving conductive structures, what implies a weak transmission of the light. Such large thicknesses are necessary because Cu diffuses strongly into the MoO₃ films. We show that the Cu diffusion can be strongly limited by sandwiching the Cu layer between two Al ultra-thin films (1.4 nm). The best structures are glass/MoO₃ (20 nm)/Al (1.4 nm)/Cu (18 nm)/Al (1.4 nm)/MoO₃ (35 nm). They exhibit a transmission of 70% at 590 nm and a resistivity of 5.0 · 10^− 4 Ω cm. A first attempt shows that such structures can be used as anode in organic photovoltaic cells.     

Morphological study of metal/dielectric composite films with various spatial distributions of metal particles

Morphological properties of metal/dielectric composite films consisting of individual metal particles in a dielectric matrix were studied by methods of computational physics. The simulated composite structures were prepared by hard-sphere and soft-sphere models with given spatial distribution of objects ranging from totally random, through various degrees of order up to anisotropic in certain directions. The images of sections of generated composite films were processed using the two strongest morphological methods - of “Voronoi tessellation” and “covariance function” with the aim to analyse the spatial distribution of particles in the composite film and to reveal the possible irregularities in this distribution. The results show that both the methods can effectively help to quantify the degree of particles arrangement as well as the anisotropy of structures studied.     

浅谈印铁设备的管理

设备管理既是企业生产组织结构的基础,又是企业正常生产经营的保障,其管理水平的高低不仅直接影响企业的产品质量和生产效益,而且还关系着企业的外在形象和市场竞争实力.印铁生产线一般都比较昂贵,如何最大可能地延长其使用寿命和使用效率,成为印铁企业设备管理的关键.本文结合本厂的实际情况,主要谈谈在不增加企业成本的基础上,如何调动人的积极性和主动性,将人和机器有机地结合起来,最大限度地提高设备的开机率?     

Metal/dielectric transmission interference filters with low reflectance. 2. Experimental results

The successful fabrication of metal/dielectric multilayer filters requires not only accurate control of the individual layer thicknesses, but also a good knowledge of the optical constants of the materials used in the filters. In the case of metal films, it is also essential to know whether any transition layers are formed at the interfaces and, if so, how their thicknesses and optical constants depend on the deposition conditions. An automatic, real-time process control, magnetron sputtering deposition system was modified to permit the manufacture of metal/dielectric filters using optical monitoring techniques. To illustrate the performance of this system, two bandpass filters, a short-wavelength pass filter, and a neutral density filter were produced, all having a low reflectance for light incident on one side. The metal layers used in these filters consisted of either Ni or Ag. TheAg films could be protected from the O(2) plasma using thin Ni or Si films. Good agreement was obtained between the calculated and measured spectral transmittance and reflectance curves.     

Design and manufacture of a gradient-index axicon

A gradient-index axicon with its initial focus offset from the back surface was designed with the thin-lens approximation. Two samples were fabricated by means of the time-varying boundary condition diffusion method, which is based on the modified quasi-chemical diffusion model. Intensity profile measurements were taken along the focal region of the axicons. The samples produced extended line foci. From the intensity measurements, the central spot widths and back focal lengths were determined. The peak widths matched theoretical predictions made with the diffraction theory for the samples and showed good agreement with the predicted widths for a pseudo-Bessel beam, showing that the axicon produced a pseudo-diffractionless beam.     

空冷波纹补偿器设计与制造

空冷机组为我国热电机组首次采用空冷方式,空冷机组管道用波纹补偿器的技术参数为德国GEA公司要求,作为国内首台空冷机组用波纹补偿器的生产商,我们结合国外空冷技术资料及美国膨胀节制造商协会《EJMA》标准,做了大量细致的工作,制订了详细的设计、制造及检验方案。     

R290冷凝器的设计与制造

针对R290的性能特点和管内两相流的冷凝换热特性，设计并制造了R290／CO2复叠式制冷循环中的R290水冷式冷凝器，为自然工质R290／CO2复叠式制冷循环系统的研究和实际应用奠定基础。     

LWIR亚波长铝/硒化锌光栅偏振器设计

为提高长波红外偏振成像系统中偏振器件性能,本文通过分析光栅材料及结构参数对光栅偏振性能的影响,设计并优化了一种双层材料构成的亚波长光栅。该光栅为矩形形貌,光栅区由铝与硒化锌构成,两种材料的厚度分别为0.6 μm和0.4 μm,光栅周期1 μm,占空比50%。利用严格耦合波理论分析并计算该结构光栅的衍射效率,7~15 μm波段的光以0~60°入射后其0级横磁模透射率达到87.54%以上,消光比超过47 dB。该光栅在10.6 μm的测试波长下,TM透射率高达90.80%且具有50 dB以上的消光比,相比槽深相同的单层铝光栅,偏振透过率明显提高。仿真结果显示,该光栅在整个宽长波红外波段具有良好的偏振性能。     

Optical range microcavities and filters using multiple dielectric layers in metal-insulator-metal structures

We present a technique to adjust omnidirectional resonances in planar metallic microcavity structures. It is demonstrated numerically with realistic material parameters that by changing the thickness of different dielectric layers in metal-dielectric-metal structures, the omnidirectional resonance can be chosen to lie at an arbitrary frequency in the optical range. These ideas can also be applied to design a high-pass filter in the optical frequency range.     

Modelling of metal/dielectric composite films — From sphere to columnar inclusions

Composite films consisting of metal inclusions of various shapes embedded into a dielectric matrix were created by computer experiments using a brand-new model. Obtained structures were analyzed as concerns the correlation between morphological and transport properties (the percolation threshold). It was found that the inclusion shapes (ellipsoids) and inclusion arrangements (columnar structures) influence the percolation threshold in such a way that (i) the more different the shapes from spheres are, and (ii) the more random the structures is the lower value of the percolation threshold one can expect.     

Design of withdrawal-weighted SAW filters

Presents a new design algorithm for a withdrawal-weighted surface acoustic wave (SAW) transversal filter. The proposed algorithm is based on the effective transmission loss theory and a delta function model of a SAW transversal filter. The design process consists of three steps, which eventually determine eight geometrical design parameters for the filter in order to satisfy given performance specifications. First, the number of fingers in the input and output interdigital transducers (IDTs), plus their geometrical sizes is determined using the insertion loss specification. Second, the number and positions of the polarity reverses in the output IDT are determined using the bandwidth and ripple specifications. Third, the number and position for withdrawing and switching specific fingers in the output IDT and attached electrode area are determined to achieve the desired sidelobe level. The efficiency of the technique is illustrated using a sample design of an IF filter consisting of a uniform input IDT and withdrawal-weighted output IDT     

Design and manufacture of all-dielectric nonpolarizing beam splitters

Past research on all-dielectric nonpolarizing beam splitters is reviewed. It is shown that, for a 50-nm spectral region, it is possible to design and manufacture a two-material nonpolarizing plate beam splitter for use at an angle of 45 degrees (with a measured rms reflectance of 0.50 +/- 0.01 for both s- and p-polarized incident light).