多层介质光学膜系的计算机模拟误差分析

用计算机数值计算方法模拟多层介质光学膜系的实际镀膜工艺过程，分析膜厚误差对λ0／4高反射膜系透射率和反射率的影响，讨论在一定技射率要求条件下不同层数膜系的允许厚度误差。发现当膜层偏离λ膜厚时，光学厚度控制工艺能通过自动调整其后膜层的厚度有效地降低厚误差对膜系透射率和反射率的影响。对于镀制高反射率膜而言，膜厚允许误差仍可有较大的范围。     

掺杂半导体/金属膜系的光谱透射反射特性

提出了以改变半导体薄膜的掺杂浓度来调节它的等离子体频率ω_p,使它的高透射区移至可见光带.选择本征吸收频率在近紫外区的金属与之构成最佳的D/M光谱透射-反射膜系,同时结合掺杂半导体膜与金属膜的最佳厚度组合以形成较理想的透明隔热复合膜. 关键词：     

含n＝k超薄金属膜的周期对称膜系的性质及窄带高反膜设计

本文阐述了n≈k的超薄金属膜与介质膜组成周期对称膜系的光学特性,并结合Ag、Al等膜层的高反特性提出了可见光区诱导窄带高反膜系结构,推导出膜系的反射率、反射峰值、反射半波带宽等光谱反射特性的近似公式,实验证实了理论设计和分析.同时也提出了设计红外和紫外窄带高反滤光片的方法.     

宽截止窄带高反射滤光膜设计

窄带高反射滤光膜在光通讯、光学探测仪器等领域有着重要应用.探讨了"基片|H(LH)m1aL(HL)m2βCr,M|空气"膜系结构的窄带高反射滤光膜系,讨论了金属Cr层厚度,以及两种不同的匹配膜系对滤光膜特性的影响,计算了Cr层内部的电场分布.结果表明,较厚的金属层可实现更宽的截止带宽,匹配层的加入有效地实现了宽截止带的深截止,使中心波长处导纳为较大值的匹配膜系可以更好地实现滤光膜宽截止、窄带高反射特性;匹配膜层使中心波长处Cr层内部的电场强度趋于零,有效地降低了整个膜系的吸收,提高了反射率.     

一类低反射率分形膜系的设计

讨论了一类分形电磁波吸收膜层的设计.基于一种简化模型解析计算了膜系反射率,并得出了一系列选择膜层材料以降低反射率的判据.对由这些判据所选的一些理想和实际材料所构成的膜系的反射率进行了数值模拟.结果表明,符合材料判据构成的分形膜系的反射率会随分形级数的增加而逐渐降低.最低的平均反射率为0.01. 关键词： 分形 薄膜系 电磁波吸收     

一维光子晶体与光学多层介质膜

本文阐述了一维光子晶体和光子禁带的概念,对比了一维光子晶体与光学多层介质膜在结构和特性方面的联系和差别,运用薄膜光学的理论和方法讨论了多层介质膜的高反射带与光子禁带和膜系结构参量的关系.     

兼容型低目标特征涂层

掺锡氧化铟（ITO）薄膜同时具备在近红外波段的低反射和红外波段的高反射特性,其介电常数可由Drude自由电子模型描述。SiO薄膜在特定的红外波长处有很强的吸收。将二者结合,可实现特定的光谱选择性。本文对SiO/ITO膜系的光谱选择性进行了研究,讨论了膜系结构对反射光谱的影响。通过用特征矩阵计算反射光谱,发现适当调整膜系的组合方式及选择膜层参量,用SiO/ITO膜系可以做成兼容型红外低目标特征涂层。     

用Kramers-Kronig关系求出反射镜的相位色散

光学元件相位色散在超短光脉冲的产生和传播中起着重要的作用,本文提出运用Kramers-Kronig关系,从反射谱直接求出反射镜的相位色散.文中对此法作了分析并以多层介质膜和铝膜反射镜为例子进行了讨论.     

等效腔法研究低损介质镜的反射特性

利用多光束干涉原理的等效腔模型对四分之一波长多层介质镜进行了研究。证明在反射镜中心频率ωo附近，形为ρ(ω)exp[iψ(ω)]的反射系数中的ρ(ω)等于ρ(ω)，ψ(ω)与频率成正比。求得了在介质具有微弱吸收情况下，吸收引起的四分之一波长镜反射下降和反射时延的表达式，研究了反射率下降以及反射时延与膜层数目的奇偶性的关系。在此基础上还引入了一个具有一定普适性的权重因子，通过这个权重因子可以定量描述镜子中各层对多层介质镜反射率下降、反射时延等重要特性的影响。     

一维光子晶体禁带调制的几种方法

基于传输矩阵法用Matlab软件对TiO_2-SiO_2光子晶体的反射谱进行了模拟.在介质层光学厚度满足四分之一膜系条件下,研究了入射角、介质厚度和光子晶体周期数对禁带的影响,并给出了通过改变这些参量实现对禁带调制的方法.     

Method of the ratio of envelopes of the reflection spectrum for measuring optical constants and thickness of thin films

A spectrophotometric method is proposed that uses the ratio of envelopes of minima and maxima of the interference reflection spectrum for measuring optical constants of a film on a substrate. Because this ratio does not contain the instrumental function of a spectrophotometer, there is no need in careful calibration of the spectrophotometer. In the case of a transparent isotropic film on an absorbing substrate, the inverse problem has an analytic solution. A simple method is proposed for numerical calculations of the optical constants and thickness of an absorbing film.     

Reflection characterization of anisotropic ultrathin dielectric films on absorbing isotropic substrates

The reflection of linearly polarized light from an ultrathin anisotropic dielectric film on isotropic absorbing substrate is investigated analytically in the long-wavelength limit. All analytical results are correlated with the numerical solution of the anisotropic reflection problem on the basis of rigorous electromagnetic theory. Simple analytical approach developed in this work not only gives a physical insight into the reflection problem but also provides a way of estimating the necessary experimental accuracy for optical diagnostics by reflection characteristics. It is shown that obtained expressions are of immediate interest for determining the parameters of anisotropic surface layers. Innovative possibilities for optical diagnostics of anisotropic properties of ultrathin dielectric layers upon absorbing materials are discussed.     

Reflection refractometry for nearly normal incidence and at the Brewster angle

We consider and experimentally study two reflection refractometry methods involving reflection of light from the optical surface of a material for nearly normal incidence and for incidence at the Brewster angle. We analyze the sources of error in the methods, and show that it is possible to use laser radiation to measure the refractive index of materials to four decimal places. We note the advantages of the methods in preparing samples for measurements in the case of solid, liquid, film, and weakly absorbing materials.     

Optical parameters of epitaxial GaN thin film on Si substrate from the reflection spectrum

A method has been proposed for determining the optical properties of a thin film layer on absorbing substrates. The film optical parameters such as thickness, refractive index, absorption coefficient, extinction coefficient and the optical energy gap of an absorbing film are retrieved from the interference fringes of the reflection spectrum at normal incidence. The envelopes of the maxima of the spectrum E_M and of the minima E_m are introduced in analytical forms to find the reflectance amplitudes at the interfaces and approximate values of the thin film refractive index. Then, the interference orders and film thickness are calculated to get accurate values of the needed optical parameters. There are no complex fitting procedures or assumed theoretical refractive index dispersion relations. The method is applied to calculate the optical properties of an epitaxial gallium nitride thin film on a silicon (1 1 1) substrate. Good agreement between our results and the published data are obtained.     

一种新型红外低目标特征材料

现代探测系统由单一工作模式到复合工作模式的转变,对低目标特征材料的光谱特性提出了某些特殊要求。在文章中,基于一维掺杂光子晶体,设计了一种新型红外低目标特征材料,并研究了其复合结构对反射光谱的影响。发现在一定条件下,可以在反射光谱中的一个宽的高反射率波段内形成局部的狭窄低反射率区,从而为新型红外功能材料的研制提供了参考。     

Laser probing of anisotropic ultrathin dielectric films on absorbing materials via differential reflection characteristics

The reflection from an ultrathin anisotropic film on an isotropic absorbing substrate is investigated in the long-wavelength limit. The analytical expressions for the differential reflection characteristics of s- and p-polarized electromagnetic plane waves are obtained. All analytical results are correlated with the numerical solution of the reflection problem on the basis of rigorous electromagnetic theory for anisotropic medium. The possibilities of using the obtained approximate formulas for resolving the inverse problem for ultrathin anisotropic dielectric films upon absorbing substrates are discussed.     

透0.45 μm～1.6 μm反8 μm～12 μm宽光谱分色滤光片的制备

光谱分色滤光片对成像光谱技术至关重要,是实现光电仪器体积小、质量轻的一个重要器件.根据金属膜具有高反射率的特点和可以进行诱增透的原理,介绍了透0.45 μm～1.6 μm反8 μm～12 μm光谱分色滤光片的膜料选择和膜系设计,并应用JGP560A2型磁控溅射镀膜机制备出了光谱性能和理化性能较好的宽光谱分色滤光片,其光谱性能达到0.45 μm～1.6 μm波段范围内,平均透过率大于80%;8 μm～12 μm波段范围内,平均反射率大于91%.     

Large Positive and Negative Lateral Displacements from Total Internal Reflection Configuration with a Weakly Absorbing Dielectric Film

It is theoretically shown that the simultaneously large positive and negative lateral displacements will appear when the resonant condition is satisfied for a TE-polarized light beam reflected from the total internal reflection configuration with a weakly absorbing dielectric film. Appearance of the enhanced negative lateral displacement is relative to the incidence angle, absorption of the thin film and its thickness. If we select an appropriate weakly absorbing dielectric film and its thickness, the simultaneously enhanced positive and negative lateral displacements will appear at different resonant angles. These phenomena may lead to convenient measurements and interesting applications in optical devices.     

反射干涉光谱法测量固体薄膜的光学常数和厚度

本文报道一种简单的方法,从平原介质薄膜的反射干涉光谱来计算薄膜的光学常数和厚度。当一束光照射在基板上的介质膜上时,由于膜上下界面反射光的相干,会使反射光谱的曲线有一定的波动。我们对反射相干光谱进行理论分析,给出计算公式,从测量曲线中的实验值得出薄膜的光学常数ｎ、ｋ以及厚度等参数。此种方法简单可行,而且易于编程处理。