深紫外光刻光学薄膜

深紫外波段是目前常规光学技术的短波极限,随着波长的缩短,深紫外光学薄膜开发面临一系列特殊的问题;而对于深紫外光刻系统这样的典型超精密光学系统来说,对薄膜光学元件提出的要求则更加苛刻。本文主要介绍了适用于深紫外光刻系统的薄膜材料及膜系设计;对薄膜沉积工艺、元件面形保障、大口径曲面均匀性等超精密光学元件的指标保障关键问题进行了讨论;对环境污染与激光辐照特性等光刻系统中薄膜元件环境适应性的重要因素进行了深入分析。以上分析为突破高性能深紫外光刻光学薄膜开发瓶颈,更好地满足深紫外光刻等极高精度光学系统的应用需求指明了方向。     

Superscattering-enhanced narrow band forward scattering antenna

We present a narrow band forward scattering optical antenna which is based on the excitation of distinctive whispering gallery modes(WGMs). The antenna is composed of three coaxial cylinder layers: a dielectric layer is sandwiched between a metallic core and cladding. Owing to the destructive interference between the scattering of the outer metallic cladding and the WGM in the backward direction, the power flow in the forward direction is increased. Simulation and analysis show that in proper geometry conditions, the cavity can be tuned into a superscattering state. At this state, both the zeroth and the first order of WGM are excited and contribute to the total scattering. It is shown that the power ratio(power towards backward divided by power towards forward) can be enhanced to about 27 times larger than that for a non-resonant position by the superscattering. Owing to the confinement of the cladding to WGMs, the wavelength range of effective forward scattering is considerably narrow(about 15 nm).     

Comparative studies of absorptance behaviour of alkaline-earth fluorides at 193 nm and 157 nm

Absorptance losses in MgF₂, CaF₂ and BaF₂ during 193-nm (DUV) and 157-nm (VUV) irradiation are investigated by employing a high-resolution laser calorimetric technique which allows the determination of both single- and two-photon absorptance at energy densities up to 110 mJ/cm². A strong wavelength dependence of the DUV and VUV absorption characteristics is observed: while effective two-photon absorption takes place at 193 nm, either no similar effect at all (in the case of BaF₂) or only a very minor effect (CaF₂) is observed at 157 nm. A first explanation for this absorption behaviour is given, implying the energetic band structure of CaF₂. In addition it is shown that, due to the strong nonlinear dependency, above a critical energy density the absorptance at 193 nm can exceed the absorptance at 157 nm. Furthermore, different single- and two-photon absorption coefficients are determined for different CaF₂ samples at 193 nm, indicating a two-step absorption mechanism. In addition, laser-induced aging is found in a MgF₂ sample at 193 nm, but not at 157 nm. Received: 21 June 2001 / Revised version: 2 November 2001 / Published online: 7 February 2002     

Optical properties of pigmented coatings taking into account particle interactions

A T-matrix approach is used to obtain the orientation-averaged scattering and absorption cross sections of randomly oriented particle clusters, and the average angular distribution of the radiation scattered by them. The coefficients involved in the expansion of the phase function are obtained from this T-matrix approach, and used in a multiple scattering formalism to characterize the angular distribution of the diffuse radiation propagating through a particulate coating perpendicularly illuminated with collimated visible radiation. Asymmetry between forward and backward propagating diffuse radiation intensities is taken into account by means of this multiple scattering approach, which is based on solving the radiative transfer equation for successive scattering order contributions. A four-flux model is applied to compute the reflectance in terms of wavelength of the incident radiation and particle concentration. An application of the formalism is carried out to predict the optical properties of titanium dioxide pigmented polymer coatings, in terms of the pigment volume fraction and the degree of aggregation.     

Deep‐UV tip‐enhanced Raman scattering

We report for the first time the tip‐enhancement of resonance Raman scattering using deep ultraviolet (DUV) excitation wavelength. The tip‐enhancement was successfully demonstrated with an aluminum‐coated silicon tip that acts as a plasmonic material in DUV wavelengths. Both the crystal violet and adenine molecules, which were used as test samples, show electronic resonance at the 266‐nm excitation used in the experiments. With results demonstrated here, molecular analysis and imaging with nanoscale spatial resolution in DUV resonance Raman spectroscopy can be realized using the tip‐enhancement effect. Copyright © 2009 John Wiley & Sons, Ltd.     

Open-path trace gas detection of ammonia based on cavity-enhanced absorption spectroscopy

A compact open-path optical ammonia detector is developed. A tunable external-cavity diode laser operating at 1.5 μm is used to probe absorptions of ammonia via the cavity-enhanced absorption (CEA) technique. The detector is tested in a climate chamber. The sensitivity and linearity of this system are studied for ammonia and water at atmospheric pressure. A cluster of closely spaced rovibrational overtone and combination band transitions, observed as one broad absorption feature, is used for the detection of ammonia. On these molecular transitions a detection limit of 100 ppb (1 s) is determined. The ammonia measurements are calibrated independently with a chemiluminescence monitor. Compared to other optical open-path detection methods in the 1–2 μm region, the present result shows an improved sensitivity for contactless ammonia detection by over one order of magnitude. Using the same set-up, a detection limit of 100 ppm (1 s) is determined for the detection of water at atmospheric pressure. Received: 19 January 2000 / Revised version: 6 March 2000 / Published online: 7 June 2000     

Mn:KNSBN晶体中背向光散射与光学二极管效应

用单束毫瓦级的632.8nmHe-Ne激光入射到掺Mn的KNSBN晶体中,观察到强烈的背向散射,同时观察到一种与背向散射相联系的光学二极管效应。在一定范围内,光学二极管的时间响应常数τ与晶体表面的入射光强成反比,以K₉玻璃片作反馈镜,可将τ降低一个数量级。已取得τ=1.5s及大于15.3的正、反向透过率比。对实验结果给出理论解释。 关键词：     

多层光学薄膜矢量散射的理论与实验研究

本文提出一种用以计算多层光学薄膜的矢量散射波场分布的新方法。并应用统计学原理,详细讨论了不同膜层界面的互相关模型及相应的光学薄膜散射特性。推导中应用了薄膜光学的惯用概念,所得公式亦比较简洁。还实验测量了光学薄膜的散射波场分布,并根据所建立的模型确定了所测光学薄膜的界面互相关特性。 关键词：     

电子束蒸发氧化锆薄膜的粗糙度和光散射特性

利用电子束蒸发工艺，以Ag层为衬底，沉积了中心波长为632.8nm的氧化锆(ZrO₂)薄膜，膜层厚度在80—480nm范围内变化.研究了不同厚度样品的粗糙度变化规律和表面散射特性.结果发现，随着膜层厚度的逐渐增加，其表面均方根(RMS)粗糙度和总积分散射(TIS)均呈现出先减小后增大的趋势.利用非相关表面粗糙度的散射模型对样品的TIS特性进行了理论计算，所得结果与测量结果相一致. 关键词： 氧化锆 表面粗糙度 标量散射 电子束蒸发     

A novel Raman optical activity instrument operating in the deep ultraviolet spectral region

Raman optical activity (ROA) has been exclusively observed in the visible (VIS) and near‐infrared (NIR) spectral regions to date. During the last few years, we have designed, constructed and tested the first ROA instrument, operating in the deep‐ultraviolet (DUV) spectral region employing 244‐nm excitation. This novel DUV ROA instrument is based on a backscattering geometry and incident circular polarization modulation (ICP); it makes use of a fast DUV imaging lens‐based spectrograph and specially designed DUV grade polarization optics. The performance of this instrument has been evaluated by analysing measured non‐resonant DUV ROA spectra of non‐absorbing enantiomeric liquid samples and by comparing these with corresponding ROA spectra recorded in the visible spectral region. Copyright © 2015 John Wiley & Sons, Ltd.     

Bending-induced optical loss in random-hole optical fibers

We present the experimentally determined optical bend loss for random hole optical fibers in the spectral range 1520 to 1570 nm induced by wrapping the optical fiber around a fixed diameter mandrel. The optical losses are compared to those obtained for a single-mode fiber and a multimode fiber using the same bending procedures. The bending induced optical losses in the random hole optical fibers were several orders of magnitude lower than for the single-mode fiber and were about 1 order of magnitude lower than for the multimode fiber.     

Origin of delocalization in organic molecular conductors

The delocalization of electron states in one-dimensional metals, such as TTF-TCNQ, accounts for the observed itinerant motion of the electrons at temperatures above about 50 K. This delocalization is related to the extended nature of the molecules in organic metals, which causes the amplitude for forward scattering by the phonons to exceed the amplitude for backward scattering by an order of magnitude. The large forward scattering, which delocalizes the electrons, does not contribute to the resistivity in the delocalized state.     

Investigation of Electromagnetic Complex Scattering for Spherical Targets in Ku Wave Band

This paper studies the electromagnetic reciprocity among spherical targets. The second scattering field for a target is derived in detail. The complex scattered field and the bistatic RCS are presented respectively. The simulations for the obtaining result in Ku wave band show that the size of the principal target affects greatly both the forward scatter and the backward scatter. The influence of the targets around shows definite periodicity. The second scattered field decrease with the increase of distance between two targets. The more near the forward area the rounding target is, the bigger its affect is. The magnitude of the second scattered field is about 10^–3 comparing with that of the first scattered field. The size of surrounding particles can be considered as a stated scale when researching the electromagnetic reciprocity. This kind of interaction for three dimensions can be investigated easy by using the obtained result and coordinate transformation.     

Raman scattering by optical phonons and polaritons in CuCl

We present data on forward and backward scattering in CuCl at liquid N₂ temperature. Peaks at 146 and 172 cm^-1 which appear in both forward and backward scattering spectra are attributed to other than first order scattering by optical phonons. The data on polarition scattering indicate that the atomic displacement contribution to the scattering by TO phonons is rather small. From the experimentally determined polarition dispersion curve we obtain a value of 174 ±2.5 cm^-1 for ω_T and a value of 5.3 for ?_S.     

用低压反应离子镀的方法制备Ge_(1-x)C_x单层非均匀增透膜的研究

用低压反应离子镀(RLVIP)的方法在Ge基底上制备了Ge1-xCx单层非均匀增透薄膜。随着沉积速率在0.05~0.4nm/s之间的变化,其折射率在2.31~3.42之间可变。实验结果表明,镀制的Ge1-xCx单层非均匀增透保护薄膜均为无定形结构,并实现了从2000~8000nm的宽波段增透。当沉积速率为0.1nm/s时,单面平均透过率从68.6%提高到了80.9%,比单面未镀膜时提高了17.9%。通过对薄膜的稳定性和牢固度进行测试表明,制备的Ge1-xCx单层非均匀增透薄膜具有良好的性能。     

水中受激拉曼散射的能量增强及受激布里渊散射的光学抑制

为提高液体介质中受激拉曼散射的输出能量,提出了通过温度调控来抑制受激布里渊散射的方法,设计了532 nm多纵模宽带脉冲激光泵浦的受激拉曼散射发生系统,测量了不同温度下水中前向受激拉曼散射及后向受激布里渊散射的输出能量,分析了水温、泵浦激光线宽及热散焦效应对受激拉曼散射输出能量影响的物理机制.实验结果表明:通过降低水温可实现对受激布里渊散射过程的有效抑制,同时减小热散焦效应带来的光束畸变,从而有效提高受激拉曼散射的输出能量.研究结果对液体介质中的受激拉曼散射多波长转换具有重要意义.     

溶胶-凝胶TiO2和SiO2光学膜的结构

本文研究了TiO₂和SiO₂溶胶-凝胶光学膜在低温热处理下的组分、形貌特征、光散射特性.AES分析结果表明,在TiO₂膜和SiO₂膜的交界面处,Ti和Si相互扩散,从而证实了在多层膜中,膜层之间、膜层和基底之间有Ti-O-Si(或Si-O-Ti,或Si-O-Si)化学键形成.AES和ESCA分析结果显示溶胶-凝胶膜经过低温处理后C的含量较高,这归结为溶胶—凝胶膜的工艺特点.AFM测试结果显示,溶胶—凝胶TiO₂光学膜的表面形貌具有显著的柱状结构,薄膜表面起伏大约是7.5nm.TiO₂,SiO₂单层膜的表面散射率随着热处理温度的提高而变大,对于不同陈化时间的溶液镀制的膜有不同的表面散率.     

Energy relaxation of hot carriers in single-wall carbon nanotubes by surface optical phonons of the substrate

A new mechanism is proposed for the energy relaxation of hot carriers in single-wall carbon nanotubes: scattering with the emission of surface optical phonons into the semiconductor substrate. The theory involves intrasubband and intersubband forward and backward scattering. The analytical result and numerical data indicate that intrasubband forward scattering is the main process: the corresponding lifetime comprises several femtoseconds for a quartz substrate, which allows this mechanism of energy relaxation to be considered dominating for a nanotube on the surface of a polar semiconductor or a dielectric.     

Accuracy design of ultra-low residual reflection coatings for laser optics

Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refractive index inhomogeneity to obtain gradient-index coating. In the normal structure of antireflection coatings for center wavelength at 532 nm, the physical thicknesses of layer H and layer L are 22.18 nm and 118.86 nm, respectively. The residual reflectance caused by refractive index inhomogeneity(the degree of inhomogeneous is between -0.2 and 0.2) is about 200 ppm, and the minimum reflectivity wavelength is between 528.2 nm and 535.2 nm. A new numerical method adding the refractive index inhomogeneity to the spectra calculation was proposed to design the laser antireflection coatings, which can achieve the design of antireflection coatings with ppm residual reflection by adjusting physical thickness of the couple layers. When the degree of refractive index inhomogeneity of the layer H and layer L is-0.08 and 0.05 respectively, the residual reflectance increase from zero to 0.0769% at 532 nm. According to the above accuracy numerical method, if layer H physical thickness increases by 1.30 nm and layer L decrease by 4.50 nm, residual reflectance of thin film will achieve to 2.06 ppm. When the degree of refractive index inhomogeneity of the layer H and layer L is 0.08 and -0.05 respectively, the residual reflectance increase from zero to 0.0784% at 532 nm. The residual reflectance of designed thin film can be reduced to 0.8 ppm by decreasing the layer H of 1.55 nm while increasing the layer L of 4.94 nm.     

Formation of Al2O3 coatings on NiTi alloy by micro-arc oxidation method

Rough and porous Al₂O₃ coatings containing Ca and P were prepared on Ti–50.8 at.% Ni alloy by micro-arc oxidation (MAO) technique. The microstructure, elemental and phase composition of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS) and thin-film X-ray diffraction (TF-XRD). The thickness of the coatings was measured by eddy current coating thickness gauge. The corrosion resistance and the nickel release of the coated and uncoated samples were examined by potentiodynamic polarization tests and immersion tests in Hank’s solution, respectively. The results show that the coatings are mainly composed of γ-Al₂O₃ crystal phase. The Ni content of the coatings is about 3.5 at.%, which is greatly lower than that of NiTi substrate. With increasing treatment time, both thickness and roughness of the coatings increase. The corrosion resistance of the coated samples is about two orders of magnitude higher than that of the uncoated NiTi alloy. The concentration of Ni released from coated NiTi samples is much lower than that of uncoated NiTi sample. It can be reduced in the factor of one-seventh compared with the uncoated NiTi sample after 3 weeks immersion in Hank’s solution.