共查询到20条相似文献,搜索用时 531 毫秒
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E. Xifr Prez L.F. Marsal J. Ferr-Borrull T. Trifonov J. Pallars 《Physica E: Low-dimensional Systems and Nanostructures》2007,38(1-2):172
We have designed and fabricated a porous silicon (PS) microcavity that shows a reflectivity resonance around 3 μm in between two spectral regions with high reflectivity values. The microcavity has been simulated following the photonic crystals formalism, which results in good agreement with the measured spectrum. The reflectivity spectrum of the microcavity has been analyzed under different humidity conditions. We demonstrate that the reflectivity resonance shifts to higher wavelengths and that the reflectivity decreases when the humidity increases. In addition, the reflectivity spectrum of the as-prepared device is recovered when the humidity returns to the initial laboratory conditions. Finally, the effect on the reflectivity spectrum of a condensed water layer at the surface of the microcavity is also analyzed. 相似文献
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多层膜界面粗糙度、入射光单色性对软X射线多层膜实际反射率均有影响。利用数学卷积积分,理论上推导出一个在入射光不同单色性下精确计算多层膜反射率的公式。利用给出的理论计算公式,简要分析了入射光不同单色性、不同界面粗糙度对Mo/Si多层膜反射率的影响。理论分析发现这两种因素对Mo/Si多层膜反射率影响完全不同:入射光低的单色性不但极大降低Mo/Si多层膜峰值反射率,而且使反射曲线的半峰全宽增加;而界面粗糙度是降低Mo/Si多层膜反射曲线上各点对应值,基本不改变Mo/Si反射曲线的半峰全宽,不改变反射曲线的形状。说明这两个因素在软X射线的长波段对多层膜反射性能的影响不同。 相似文献
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利用双光束反射率测量装置,研究了连续激光重复加载作用下30CrMnSiA钢金属材料的反射率变化特性。通过激光加载、冷却然后再加载到更高的温度的辐照试验与激光单次辐照的结果比较,发现二次加载时材料表面的激光反射率与样品表面首次加载时达到的最高温度所对应的反射率基本一致,只有达到并超过首次加载时样品曾达到的最高温度后,样品表面的反射率才会再次发生变化,且变化趋势与单次完整加载时的路径重合。这表明样品表面的反射率与其达到的最高温度有关,进一步的研究结果表明,样品达到的最高温度与样品表面在最高温度下产生的氧化反应层有关,而这一氧化层在冷却过程和再加载过程不变化。 相似文献
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为了消除光谱采集中操作方法对测量带来的干扰,以及提高仪器灵敏度和增强样本之间的差异性,将反射率归一化法用于光谱法舌诊数据预处理。采集被检者舌尖反射光谱,计算被测对象的反射率和归一化反射率,比较不同距离采集的同一被测对象反射率和归一化反射率发现,反射率归一化可以消除不同采集距离对反射光谱造成的影响,比较不同样本的反射率和归一化反射率曲线以及分类预测模型预测结果,结果表明反射率归一化法可以增强样本之间的差异性,增强后续疾病快速筛查模型的稳健性和预测能力。 相似文献
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磁光盘反射率是一个重要的参数,在磁光盘的研制和生产过程中必须进行测试。本文首先介绍了反射率测试的典型方法,然后结合磁光盘磁光特性伺服测试系统提出了一种测试磁光盘反射率的实用有效的方法,使磁光盘磁光特性测试仪既能测试克尔角又能测试反射率。最后对该方法测试反射率的误差进行了评估,并给出了测试实例。 相似文献
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K9和石英玻璃基片上Au膜真空紫外反射特性研究 总被引:3,自引:0,他引:3
采用离子束溅射法,分别在经过不同前期清洗方法处理过的K9及石英玻璃光学基片上,选择不同的镀膜参量,镀制了多种厚度的Au膜。对镀制的Au膜在真空紫外波段较宽波长范围内的反射率进行了连续测量。测试结果表明:辅助离子源的使用方式、Au膜厚度对反射镜的反射率有重大影响。基片材料、镀前基片表面清洗工艺等对反射率也有一定影响。采用镀前离子轰击,可显著提高Au膜反射率及膜与基底的粘合力;获得最高反射率时的最佳膜厚与基片材料、镀膜工艺密切相关。对经过离子清洗的石英基片,膜厚在30 nm左右反射率最高;比较而言,石英基片可获得更高的反射率;辅助离子源的使用还显著影响获得最高反射率时对应的最佳膜厚值,且对K9基片的影响更显著。 相似文献
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The transient time-resolved reflectivity of chromium film is studied by femtosecond pump-probe technique with a 70-fs laser. Experimental results show that the reflectivity change increases with the power of the pump laser. The fast decrease of the reflectivity occurs between 0-200 fs which is mainly due to the electron-electron interaction. Subsequencely, the slower recovery of the reflectivity between 200-900 fs is mainly due to the electron-phonon coupling process. The reflectivity after 900 fs rises little to a near-constant value for the thermal equilibrium of the system. The experimental results can be explained properly with numerical simulation of the two-temperature model. It is helpful for understanding of the electron ultrafast dynamics in chromium film. 相似文献
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The total reflectivity of tin and magnesium in ablation by nanosecond Nd:YAG laser pulses in air is studied. It was found that the high initial reflectivity of the studied metals undergoes a significant drop to values of 0.11 for Sn and 0.16 for Mg within a laser fluence range between about 0.8 and 11 J/cm2. These reduced reflectivity values remain virtually unchanged with further increasing laser fluence. This study shows that a significant reflectivity decrease of the studied metals is caused by plasma formation in front of the irradiated surface. Below the plasma formation threshold, the reflectivity of the studied metals is observed to be virtually independent of laser fluence, indicating a small role of Drude׳s temperature effect on the reflectivity of the studied samples. 相似文献
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通过数值模拟的方法研究了素混凝土、钢丝网和钢丝网混凝土板对电磁波的屏蔽和吸收性能。首先将模拟得到的素混凝土反射率和透射率曲线和试验得到的曲线进行对比。对两种不同规格的钢丝网进行了数值模拟,并与试验和理论解进行了比较,对不同直径、网径、层数的钢丝网进行了数值模拟。最后研究了钢丝网及钢丝网位置对混凝土反射和透射性能的影响。数值模拟采用三维电磁仿真软件HFSS15.0。相同网径条件下,钢丝网直径越大,反射率越大,透射率越小。钢丝网直径相同的条件下,网径越大,反射率越小,透射率越大。在混凝土中间加入钢丝网对反射率平均值大小影响很小,主要影响反射率曲线的谐振性。 相似文献
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In this paper we present the interpretation and analysis of time-resolved reflectivity measurements for excimer laser irradiated silicon. A nonequilibrium melting model is used to calculate the temperature distribution in the sample and the position of the solid-liquid interface. Calculations of the reflectivity of the probe beam are performed to obtain time-resolved reflectivity signals from basic principles, independent of the experiments, which can be compared with experimental data to reveal information about dynamics of the heating and cooling process. We propose more accurate methods for the determination of the melting threshold, the melt front position and the reflectivity of the sample for excimer laser light. From model calculations and experimental data we determine the reflectivity of the solid and liquid silicon for ArF excimer laser light. 相似文献
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A. García-Valenzuela E. Haro-Poniatowski J. Toudert R. Serna 《Applied Physics A: Materials Science & Processing》2013,110(4):757-764
The reflectivity variations of a dielectric thin film during the deposition of a disordered monolayer of metallic nanoparticles are studied. We present experimental results and provide theoretical physical insight into the behavior of the reflectivity signal and its dependence on the dielectric thin-film thickness and structural features of the monolayer of nanoparticles. A closed-form expression is used to describe the reflectivity of a disordered monolayer of particles on a flat substrate within the frame of a coherent-scattering model approach. It is shown that the model reproduces qualitatively the behavior of the reflectivity signal during the experiment. Finally we study the optical response in the limit of small particles for low surface coverage fractions of the monolayer to evidence the main parameters that dictate the evolution of the reflectivity signal during the growth of a monolayer of nanoparticles. 相似文献
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I. Rychetsky 《Phase Transitions》2013,86(11-12):1095-1098
Bounds on the effective permittivity circumscribe 2D area in the complex plane representing possible values of permittivity. It is shown that the corresponding possible values of reflectivity occur within the interval determined by the lowest and the highest reflectivity value, which represent minimum and maximum values of reflectivity found at the permittivity bounds. 相似文献
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Abdelouahab Hamadou 《Chinese Journal of Physics (Taipei)》2018,56(3):1286-1295
The effect of external reflectivity on the dynamic behaviors of quantum cascade laser coupled to external cavity is theoretically investigated. Our model is based on three-level rate equations including the dependence of the loss on external cavity parameters. We find in particular that the effective reflectivity, photon lifetime and threshold current are strongly influenced by the external cavity length and external reflectivity. The optimum external cavity length (Lext) is about 4?cm. We also show that the external cavity reflectivity influences significantly the dynamics of the electron number in the upper and lower laser levels, population inversion, and photon numbers in the Fabry Perot and in the external cavities. In addition, the external cavity reflectivity dependences of turn-on delay time (tth) is also studied and discussed. 相似文献
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In the framework of the independent-hot-spot model, it is shown that the reflectivity resulting from scattering instabilities when a spatially smoothed laser beam interacts with a plasma exhibits large statistical fluctuations near threshold. The importance of the fluctuations is discussed in terms of a confidence interval for the reflectivity, which is more relevant to experimental measurements than the average reflectivity. An analytical model for the fluctuating reflectivity is developed and shown to be in good agreement with numerical simulations. The influence of the transverse size of the interaction region is studied. 相似文献
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A. Aschentrup W. Hachmann T. Westerwalbesloh Y.C. Lim U. Kleineberg U. Heinzmann 《Applied Physics A: Materials Science & Processing》2003,77(5):607-611
We present a method of deriving single layer thickness fluctuations of Mo/Si EUV multilayers from cross-sectional high-resolution transmission electron microscopy micrographs. The obtained thickness values for each layer are used in a layer model to calculate the grazing-incidence X-ray reflectivity (GIXRR) and the corresponding at-wavelength-reflectivity curves. Comparison with XRR measurements shows the strong effect of thickness fluctuations on the intensity of the secondary Kiessig fringes and the main Bragg maxima. This model results in substantially better reflectivity simulations than the standard periodic four-layer model or the assumption of statistically distributed (random) thickness errors. Results for reflectivity curves at 13-nm wavelength are discussed in terms of peak reflectivity, peak shift and further changes in the shape of the reflectivity curve. PACS 68.65.Ac; 68.37.Lp; 41.50.+h 相似文献