Second harmonic generation of light in the Kretschmann attenuated total reflection geometry in the presence of surface roughness

Abstract

Using a computer simulation approach we study the generation of second harmonic light in reflection and in transmission in the Kretschmann attenuated total reflection geometry. In this geometry a thin metal film is deposited on the planar base of a dielectric prism, through which p-polarized light is incident on the film. The back surface of the film, which separates the film from vacuum, is a one-dimensional, randomly rough surface, whose generators are normal to the plane of incidence of the light. The nonlinearity responsible for the second harmonic generation is assumed to arise at the prism-metal and metal–vacuum interfaces, and thus enters the problem only through the boundary conditions at these interfaces at the harmonic frequency. The source terms entering these boundary conditions are obtained from the solutions of the corresponding scattering and transmission problems at the fundamental frequency. It is found that a peak in the angular dependence of the intensity of both the transmitted and reflected second harmonic light occurs in the directions normal to the mean scattering surface, in addition to an enhanced backscattering peak in the retroreflection direction. The enhanced transmission peak occurs in the non-radiative region, and therefore cannot be observed in the far field.     

Absorption Measurement Using a Leaky Waveguide Mode

We propose an optical waveguide sensor using a leaky mode for absorption measurement of liquid samples. This sensor uses a single coupling prism. A cladding layer and a waveguide layer are directly deposited on the reflecting surface of the prism. The intensity of the internally reflected beam at an appropriate incident angle is very sensitive to the imaginary part of the sample attached to the surface of the waveguide layer. The sensitivity of this sensor is controlled by the thicknesses of both cladding and waveguide layers. We studied the performance of the sensor by numerical calculation.     

Angle-dependent infrared absorption spectroscopy at electrode/electrolyte interfaces

Angle-dependent internal reflection spectroscopy is performed in the attenuated total reflection setup for an electrochemical cell with a Fourier transform infrared spectrometer. The working electrode is a thin Pt film evaporated onto a hemispherical Si prism. The refractive index of the Pt film obtained from the experiment is found to differ from the value for bulk material. The difference is ascribed to the surface corrugation of the Pt surface and the film thickness in the nanometer range. The function of reflection intensity versus angle of incidence changes significantly when a resonant absorption occurs in the electrolyte medium. The angle-dependent absorption band intensity of CO adsorbed on the Pt film under potential control reveals changes in magnitude and an inversion of the band for different angles of incidence. This behaviour is explained by the excitation of resonant surface plasmon waves at the Pt/electrolyte interface and by multiple reflections occurring at the interfaces. A simulation for the three-layer system Si/Pt/electrolyte agrees with the experimental results.     

Surface plasmon enhanced Brillouin scattering from metal films

The theory of Brillouin scattering in a prism-metal film-air (Kretschmann) geometry is analyzed and numerical estimates are given for a LaSF9 prism-Ag film-air configuration. Signal enhancement of several orders of magnitude is predicted under conditions of coupling to surface plasmon-like fields.     

空气隙厚度对格兰-泰勒棱镜透射光强扰动影响的理论分析

以格兰–泰勒棱镜为例,根据实验现象对透射光强随旋转角扰动的原因进行了理论分析。通过泰勒棱镜的单色偏振光束在空气隙处发生多束光的干涉,使得透射光强依赖于入射角的大小。实验中棱镜振动引起入射角的微小扰动,导致了透射光强的扰动。着重分析了泰勒棱镜空气隙的厚度对于扰动的影响,并在此基础上讨论了减小扰动的方法,通过选取合适的空气隙厚度以及对棱镜的结构角做相应的调整可有效地减小扰动。     

空气隙偏光镜对单模高斯光束光强分布影响的分析

根据光在格兰泰勒棱镜和格兰傅科棱镜空气隙胶合层中的干涉效应,分析了空气隙偏光棱镜对单模高斯光束光强分布的影响;结果表明:对于某一波长的入射光,当空气隙的厚度一定时,透射光强随光在空气隙介面上入射角的变化作周期性振荡;当入射角一定时,透射光强随空气隙厚度的变化作周期性变化;且透射高斯光束的形状也随光的入射角以及空气隙厚度的改变发生变化;且无论是透射光强的周期性振荡,还是透射高斯光束的形状的变化,格兰泰勒棱镜的影响均小于格兰傅科棱镜;这说明前者的综合性能优于后者。     

马普-赫斯棱镜对单模高斯光束光强分布影响分析

根据光在马普－赫斯棱镜两空气隙胶合层中的干涉效应,分析了其对单模高斯光束光强分布的影响.结果表明,对于某一高斯光束入射棱镜时,透射光束光强将随入射角的变化而呈现周期性的振荡;对于正入射的光束,当空气隙的厚度一定时,透射光强随棱镜两空气隙结构角的变化作周期性振荡;当结构角一定时,透射光强随空气隙厚度的变化作周期性变化;且透射高斯光束的形状也随棱镜结构的改变发生变化,表明,可以通过选择合适的棱镜结构以减小棱镜对透射光束的影响,对于成品棱镜,则可通过改变入射角使棱镜的性能达到较佳状态.     

Light refraction from air in glass in the case of light beam departure from the refracting surface

The effect of light refraction in the case of a light beam departing from the refracting face of a prism is examined in this paper. It is established that the refracted flux diminishes to zero as the angle of departure increases to 14°; the angle of refraction is independent of the angle of departure, and equals the angle of refraction of glazing rays. The nature of the distribution of the refracted ray intensity along the refracting face is determined. Data are presented about the intensity distribution in the refracted beam at the exit from the prism and in the plane of the radiation detector.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 55–58, December, 1987.The author is grateful to V. E. Zuev and S. D. Tvorogov for attention to the research and discussion of its results.     

金纳米粒子组装体系的表面增强拉曼光谱特性研究——表面粒子密度与拉曼光谱强度的关系

利用纳米粒子组装制备了金基底———巯基苯胺自组装膜偶联层———金纳米粒子的“三明治”结构,研究了表面粒子密度与偶连层分子的拉曼光谱强度的关系。实验结果显示,该结构对偶连层分子的拉曼光谱有很好的增强效应,增强因子可达１０５。在表面粒子密度较低时,拉曼光谱强度与表面粒子密度曲线呈线形,随着表面粒子密度的增加,曲线出现负偏差并在粒子密度较高区域出现一个平台。     

双沃拉斯顿棱镜光强分束比精确分析

利用折射定律,介质膜两侧折射率不同时多光束干涉理论和菲涅耳公式,精确推导了双沃拉斯顿棱镜的光强分束比的具体表达式。以公式为基础,通过Matlab软件数值模拟作图分析光强分束比随入射角、入射波长和结构角的变化关系曲线。结果表明:在棱镜为介质胶合型时,光强分束比随入射角和入射波长的变化很小,光强分束比基本为1;棱镜为空气胶合型时,光强分束比随入射角,结构角和波长的变化很大。两种情况下,光强分束比随各参量的变化基本呈周期性变化。     

聚敛光下的Wollaston棱镜光强分束比研究

从棱镜的结构特点出发,利用折射定律和菲涅耳公式,推导了Wollaston棱镜对聚敛光的光强分束比随方位角的变化关系式。在入射角给定的情况下,分析了方位角对光强分束比的影响。结果表明:在入射角取定值时,方位角对光强分束比的影响基本呈二次曲线型变化;当方位角在160°～180°时,光强分束比最小。     

Simultaneous determination of the X-ray refractive index and the attenuation length from a single digitally registered radiograph of rectangular prisms

Prisms deflect and disperse X-rays due to refraction very similar to visible light. As X-rays are always attenuated while traversing material, the intensity distribution in the transmitted beam carries information about the prism transmission function. This study will show that sufficient information is contained in a single digitally registered radiograph from a rectangular prism, for deriving both the refractive index of the material and its attenuation length. The measured data can be prepared such that neither intensity fluctuations nor false light content in the incident beam will introduce systematic errors into the result. The strategy is thus very adapted, when single shot pictures are taken at X-ray sources with limited shot reproducibility. This technique is favourably be used at very grazing angles of incidence of the order of the critical angle for the prism material, when the beam deflection becomes significant. In such a geometry dimensional parameters, like sample thickness, do not affect the data analysis, which is particularly insensitive to even significant errors in the tip angle.     

光波导技术同步测量棱镜及波导薄膜参数

依据全反射理论和棱镜耦合原理,实现了对棱镜折射率及波导薄膜材料折射率和厚度的同步测量。使用高准直半导体激光器激光入射到棱镜内部与波导膜的分界面上,逐步旋转棱镜或改变棱镜的入射角,得到棱镜耦合M线,曲线前面几组的波谷为波导模激发,在M线左侧收尾处有一个不完整波峰,其反射光强随入射角迅速衰减,为全反射时的临界点,由此可实现棱镜及波导薄膜参数的同步测量;用此法测量了棱镜耦合一体化平面波导棱镜的折射率和聚甲基丙烯酸甲酯(PMMA)聚合物波导薄膜的折射率和厚度。测量棱镜折射率精度为±1.9×10-4,波导薄膜折射率和厚度的精度分别为±6.2×10-4 μm和±1.6×10-2 μm。     

偏光棱镜调制器调制光强扰动的理论分析

以格兰-泰勒棱镜为例，根据实验现象对透射光强随旋转角扰动的原因进行了理论分析。实验中发现，透射光强曲线随着入射角的微小变化而偏离马吕斯定律，出现了周期性扰动。通过格兰-泰勒棱镜的单色偏振光束产生的干涉，再加上晶体-空气隙界面处反射比的因素，使得出射光强依赖于入射角。引入了扰动因子的概念，并系统讨论了扰动因子所造成的影响，从而得出了减小扰动的方法。理论研究结果与实验符合较好。为偏光棱镜的优化设计、生产及使用提供了理论基础。     

双Wollaston棱镜光强分束比研究

利用折射定律和菲涅耳公式,研究了双Wollaston棱镜的光强分束比随入射光波长、棱镜结构角以及入射角等参量的变化关系,并进行了实验验证.结果表明：光强分束比随入射光波长的增大呈线性递减趋势;棱镜的结构角越小,光强分束比也越接近1;入射角对光强分束比的影响基本呈二次曲线型变化;当光正入射时,光强分束比最接近于1.给出了理论曲线和实验值的对比.     

On the use of the Rosseland and Planck mean absorption coefficients in the non-equilibrium radiative transfer equation

The use of the Rosseland and Planck mean absorption coefficients in the non-equilibrium (time-dependent) radiative transfer equation is investigated in the gray approximation for a prescribed temperature distribution. The corresponding gray radiative flux at the surface of a halfspace is compared to an exact (multi-frequency) solution obtained from multiple collision theory. An improved mean absorption coefficient is then obtained using the exact angle integrated intensity at the surface, and the corresponding gray approximation is shown to be markedly accurate.     

格兰-汤普森棱镜透射光强扰动的温度效应

线偏振光正入射的情况下,格兰汤普森棱镜的透射光强随入射光方位角的变化出现周期性增强的扰动,影响了透射偏振光的质量.为了尽可能的减小扰动带来的不利影响,以保证棱镜使用过程中透射偏振光的质量,通过对不同温度下扰动因子的变化分析得到了:透射光强对入射角敏感的依赖关系.实验中,格兰汤普森棱镜的振动引起入射角在棱镜的结构角大小附近作微小变化,从而导致了透射光强的扰动,选取合适的结构角可以减小扰动.对于特定波长的入射光而言,应在允许范围内尽量减小胶合层厚度;当温度在一定范围内变化时,选取结构角为平均值温度所对应的极大值点也可以减小扰动所造成的影响.     

Charge-transfer enhancement in infrared absorption of thiocyanate ions adsorbed on a gold electrode in the Kretschmann ATR configuration

The intensity of an enhanced infrared absorption of SCN⁻ ions adsorbed on an Au film electrode reaches a maximum at a negative electrode potential, where the number of adsorbed ions should be smaller than at higher potentials. In addition, the enhancement of infrared absorption is restricted to species adsorbed directly on the electrode surface. These observations suggest that a charge-transfer enhancement is working on the infrared absorption of the SCN⁻/Au electrode system. A probable precursor of the thiocyanato complex of Au was detected in the same system.     

IR absorption enhancement for physisorbed methanol on Ag island films deposited on the oxidized and H-terminated Si(111) surfaces: effect of the metal surface morphology

Infrared absorption measurements using a multiple internal reflection geometry are reported for condensed methanol at 90 K on Ag island films deposited on the oxidized and hydrogen-terminated surfaces of Si(111). The attenuated total reflection (ATR) spectra obtained as a function of methanol exposure (up to 14 L) show that a 1-nm mass thickness of Ag island film on the oxidized Si(111) surface yields an absorption intensity 2–3 times larger than the intensity in the absence of Ag on the oxidized surface. Deposition of the same thickness of Ag on the hydrogen-terminated Si(111) surface results in approximately twice the enhancement. The different magnitudes of the enhancement are discussed based on SEM micrographs for Ag island films formed on the oxidized and H-terminated Si(111) surfaces. Received: 1 March 1999 / Accepted: 8 March 1999 / Published online: 5 May 1999     

Enhancement of THz absorption in monolayer graphene for light at Brewster angle incidence

The enhancement of absorption in graphene for light at Brewster angle incidence is investigated. It is achieved by placing a graphene on a resonant Brewster filter that incorporating a spacer layer. The absorber presents above 50% absorption at resonance, which is attributed to the excitation of guided mode resonances. The electromagnetic field intensity distributions are illustrated to intuitively confirm the physical mechanism of such phenomenon. Moreover, the influence of geometric parameters on absorption is investigated to provide a useful guidance for practical fabrication. Besides, it is found that the absorption properties not only can be controlled by adjusting the incident angle but also can be dynamically tuned by changing the Fermi level. Last, the graphene absorption can be easily extended to multichannel by only an increase in the thickness of spacer. The results open new avenues for combining graphene with general guided mode resonance structure to enable novel optoelectronics device applications.