棱镜非线性波导耦合光学双稳理论

利用菲涅耳公式计算了棱镜非线性光波导耦合.从理论上分析了该双稳器件的调制和反馈特性,模拟出不同偏置角的光学双稳曲线,能定量地分析双稳最小偏置角,双稳阈值功率等.     

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.     

Tailoring of the spectral–directional characteristics of rare-earth fluorescence by metal–dielectric planar structures

It is demonstrated that the spectrum, direction and polarization of rare-earth fluorescence can be tailored by embedding the impurity ions into a planar metal–dielectric structure (MDS). The latter was designed by spin coating a rare-earth-doped oxide film (TiO₂:Sm³⁺) onto a gold-covered glass substrate. For spectral–directional investigations of Sm³⁺ fluorescence, the MDS was attached to a semi-cylindrical prism and excited by UV light from the flat side. An angular scan revealed a strongly polarized and directional emission of Sm³⁺ from the convex side of the prism. The tuning of TiO₂ film thickness in the MDS allows a control of the polarization and direction of the emission bands. A theoretical modeling of the reflectivity of the MDS suggests that the observed angular resonances in the fluorescence emission are caused by its effective coupling with surface plasmons on the gold–dielectric interface or coupling with leaky modes in sufficiently thick dielectric films working as a waveguides.     

基于银/二氧化钛复合膜的表面等离子共振气体传感器

表面等离子体共振是一种免标记的传感技术,当介质周围的介电常数发生改变时,则SPR谐振光谱特性也会随之改变.因此表面等离子体共振传感技术已广泛应用于生物化学和环境监测等领域.由于二氧化钛(TiO2)覆盖层不仅可以保护金属层,还能调谐SPR谐振的光谱强度和谐振波长于近红外波段,应用于1550 nm的光纤传感,其氧化还原反应...     

不同衬底银膜表面等离子激元波的辐射效率

不同衬底银膜表面等离子激元波的辐射效率邓里文王恭明（复旦大学物理系上海２００４３３）ＥｆｉｃｉｅｎｃｙｏｆＥｍｉｓｉｏｎｆｒｏｍＳｕｒｆａｃｅＰｌａｓｍｏｎＷａｖｅｓｆｏｒＤｉｆｅｒｅｎｔＳｔｒｕｃｔｕｒｅｓｏｆＡｇＦｉｌｍｓＤｅｎｇＬｉｗｅｎ，Ｗａ...     

不同预淀积层银膜表面等离子激元波的辐射效率

测量了棱镜／ＬＢ膜／银膜／空气，棱镜／银膜／空气，棱镜／银膜／空气三种结构在衰减全反射条件下激发的表面等离子激元波由于银膜－空气界面粗糙度而散射以空气中的辐射效率，同时，由散射光强分布计算出表面度粗糙度参数随横向相关长度σ和表面波纹深度δ，再由σ和δ计算出理论辐射效率，理论与实验结果相符合。     

Surface plasmon optical sensor with enhanced sensitivity using top ZnO thin film

Surface plasmon resonance (SPR) is one of the most sensitive label-free detection methods and has been used in a wide range of chemical and biochemical sensing. Upon using a 200 nm top layer of dielectric film with a high value of the real part ε′ of the dielectric function, on top of an SPR sensor in the Kretschmann configuration, the sensitivity is improved. The refractive index effect of dielectric film on sensitivity is usually ignored. Dielectric films with different refractive indices were prepared by radio frequency magnetron (RF) sputtering and measured with spectroscopic ellipsometry (SE). The imaginary part ε′′ of the top nanolayer permittivity needs to be small enough in order to reduce the losses and get sharper dips. The stability of the sensor is also improved because the nanolayer is protecting the Ag film from interacting with the environment. The response curves of the Ag/ZnO chips were obtained by using SPR sensor. Theoretical analysis of the sensitivity of the SPR sensors with different ZnO film refractive indices is presented and studied. Both experimental and simulation results show that the Ag/ZnO films exhibit an enhanced SPR over the pure Ag film with a narrower full width at half maximum (FWHM). It shows that the top ZnO layer is effective in enhancing the surface plasmon resonance and thus its sensitivity.     

高反射率p-GaN欧姆接触电极

根据光学薄膜原理计算了GaN/Ti/Ag、GaN/Al和GaN/Ni/Au/Ti/Ag、GaN/Ni/Au/Al多层电极结构的反射率,得出Ag基和Al基反射电极均能在全角范围内提供较高的反射率。实验测量结果表明,反射率能高于80%的Ag基反射电极,具有低欧姆接触的电学特性。并将GaN/Ni/Au/Ti/Ag多层反射电极应用在上下电极结构的GaN基LED中。实验上采用两步合金法获得了低接触电阻、高反射率的电极结构,并引入Ni/Au覆盖层克服了Ag高温时的团聚和氧化现象。解决了Ag电极的稳定性问题,显著地提高了LED的出光效率,成功制备了具有上下电极结构的GaN基LED管芯。     

Light-induced bistability in spin transition solids leading to thermal and optical hysteresis

We investigate the behaviour of photo-excitable, bistable systems, under permanent light irradiation, in presence of relaxation towards the non-excited state. Cooperativity causes bistability of the steady state, leading to light-induced thermal and optical hysteresis (LITH and LIOH). The light-induced instability is expected to induce demixtion, i.e. the coexistence of domains of the two stable steady states. Such effects are evidenced by magnetic and reflectivity measurements on the spin-crossover solid solution: , with x= 0.3, 0.5, 0.85. Experimental data are in quantitative agreement with a simple macroscopic model which includes a non-linear relaxation term in the master equation. Received: 5 June 1997 / Accepted: 17 July 1998     

Design of near-unity transmittance dielectric/Ag/ITO electrodes for GaN-based light-emitting diodes

We designed a near-unity transmittance dielectric/Ag/ITO electrode for high-efficiency GaN-based light-emitting diodes by using the scattering matrix method. The transmittance of an ultrathin metal layer, sandwiched between a dielectric layer and an ITO layer, was investigated as a function of the thickness and the optical constant of each constituent layer. Three different metals (Ag, Au, and Al) were examined as the metal layer. The analytical simulation indicated that the transmittance of a dielectric/metal/ITO multilayer film is maximized with an approximately 10-nm-thick Ag layer. Additionally, the transmittance also tends to increase as the refractive index of the upper dielectric layer increases. By tailoring the thickness of the dielectric layer and the ITO layer, the dielectric/Ag/ITO structure yielded a transmittance of 0.97, which surpasses the maximum transmittance (0.91) of a single ITO film. Furthermore, this extraordinary transmittance was present for other visible wavelengths of light, including violet and green colors. A complex phasor diagram model confirmed that the transmittance of the dielectric/metal/ITO multilayer film is influenced by the interference of reflected partial waves. These numerical findings underpin a rational design principle for metal-based multilayer films that are utilized as transparent electrodes for the development of efficient light-emitting diodes and solar cell devices.     

On the theory of reflectivity and transmissivity of a lossless nonlinear dielectric slab

For the transverse electric polarization case (TE) we present a treatment of the optical reflectivity and transmissivity of a slab whose dielectric coefficient is a real valued function of the light intensity. If this function is numerically integrable with respect to the light intensity, our treatment can serve as an algorithm for a numerical solution of the nonlinear wave equation. If the dielectric function is proportional to the intensity, an analytical solution of the cubic wave equation is given for the electric field strength and for the phase of the field in terms of Weierstrass' elliptic functions and first elliptic theta functions, respectively. Evaluating this solution by means of a computer algebra system yields the reflectivity, transmissivity and phase dependency on the incident field intensity and on parameters characteristic for the problem. Certain combinations of the parameters lead to bistable and multivalued behavior. The solution found is used to determine the relative extrema of the reflectivity and the critical values of the thickness and of the incident intensity. The results are a generalization of linear optics results. Application of the analysis to the cubic-quintic wave equation yields the general analytic solution which is used to detemine the reflectivity of a semi-infinite nonlinear medium.     

准波导结构染料薄膜中荧光和放大自发辐射的泄漏模特性

通过理论分析和实验测量,研究准波导结构染料薄膜中荧光和放大自发辐射（ASE）的泄漏模特性。理论上,考虑薄膜传输损耗及染料吸收损耗对准波导结构中泄漏模特性的影响,通过计算准波导结构中泄漏模的光强分布,给出了相应的物理机制分析;实验上,以棱镜为衬底制备染料薄膜,根据棱镜耦合法测量不同出射角对应的泄漏模的荧光与ASE光谱,验证理论的正确性。此外,采用光束分析仪探测各泄漏模式对应的荧光及ASE的光强分布,研究了准波导结构中ASE的激励特性。结果证明,荧光峰及ASE峰的红移以及泄漏模的激发是界面反射率、薄膜传输损耗及染料吸收损耗等共同作用的结果,而界面反射率对ASE泄漏模激发特性有重要影响,染料的自吸收是荧光峰及ASE峰产生红移的主要因素。     

Quantized longitudinal exciton-polaritons in periodic metal–semiconductor nanostructures

We theoretically investigate the optical properties of one-dimensional photonic crystals composed of two alternating layers, namely a semiconductor film and a metallic one. The nonlocal optical response of the semiconductor is here described by using a resonant excitonic dielectric function, whereas the local response function of the metal film is modeled with Drude formula. We calculate optical spectra of the metal–semiconductor 1D photonic crystal for both s- and p-polarization geometries. In both cases the spectra exhibit a rich resonance structure due to the coupling of size-quantized excitons inside the semiconductor film with light. We show the difference between s- and p-polarization reflectivity as the angle of incidence is increased. In the p-polarization geometry, besides transverse exciton-polariton modes, longitudinal polarization waves are excited producing additional spectral resonances. The spectra become radically different when the frequency corresponding to the minimum of the first photonic pass-band is close to the exciton resonance, since such a frequency is distinct for s- and p-polarized modes. We also show how reflectivity spectra for both polarizations are modified with varying the metal filling fraction which controls the width of the gap below the lowest frequency band.     

Nonlinear surface plasmon polaritonic crystals

We present an overview of the optical properties of nonlinear surface plasmon polaritonic crystals and their applications to control light with light. Surface plasmon polaritonic crystals are periodically nanostructured metal surfaces or thin metal films that act as two‐dimensional photonic crystals for surface polaritons. Hybritization of such nanostructures with dielectrics exhibiting an optical nonlinear response allows utilization of the electromagnetic field enhancement effects to observe nonlinear effects and bistable behaviour at low light intensities. By changing the geometry of the nanostructured film, the dispersion of the crystal is modified and, thus, electromagnetic mode structure and associated density of states can be controllably tuned in the desired spectral range. This provides enhanced flexibility in engineering the nonlinear optical response of plasmonic crystals in a chosen spectral range for both control and signal wavelengths.     

High sum-frequency generation in dielectric/antiferromagnet/Ag sandwich structures

We present a method to increase the sum-frequency(SF) outputs in dielectric/antiferromagnet(AF)/Ag sandwich structures for a fixed input power. Two incident waves simultaneously illuminate the upper surface, one is oblique and the other is normal to it. Numerical calculations based on the SiO2/MnF2/Ag and ZnF2/MnF2/Ag structures show that the SF outputs on the upper film increase a few times as compared to those of a single AF film when the thickness of the AF film is one-quarter of the vacuum wavelength. Moreover, the SF outputs generated near the higher resonant frequency will be higher than those obtained near the lower resonant frequency. An optimum AF film thickness is achieved through investigating its effect on the SF outputs in the two different dielectric sandwich structures.     

无机厚膜发光器件绝缘层的研究

采用丝网印刷技术,在Al2O3陶瓷基板上印刷、高温烧结内电极及绝缘层,制备出陶瓷厚膜基板,进而制备了新型厚膜电致发光显示器(TDEL)。整个器件结构为陶瓷基板/内电极/厚膜绝缘层/发光层/薄膜绝缘层/ITO透明电极。研究不同结构的无机厚膜发光器件对器件性能的影响,并对器件的亮度—电压、亮度—频率进行测量。结果显示绝缘层在无机发光器件中不是单纯的保护作用,它对器件的性能有十分重要的影响。主要是对注入电子的加速作用,从而提高发光亮度。绝缘层本身对无机厚膜发光器件的发光机理没有关系。     

左手材料的反射特性与负折射率行为

利用平板波导法研究了不同入射角度下周期排列开口谐振环负磁导率材料、周期排列金属杆负介电常数材料以及左手材料微波反射特性，并利用劈尖法研究了左手材料的负折射特性.实验结果表明：负磁导率材料反射率曲线形成反射峰，其对应的反射峰频率与材料的谐振频率一致；负介电常数材料反射率接近0dB；左手材料出现单个反射较小的反射峰，其峰值反射率随入射角度的增大而变大，即反射能力增强，且反射峰与透射峰有相对频移.劈尖法测量还表明，左手材料在9800MHz频率附近出现负折射现象，其折射率n为-0.796. 关键词： 左手材料 反射 负折射率     

TE0导模干涉刻写周期可调亚波长光栅理论研究

通过棱镜耦合激发非对称金属包覆介质波导结构中的TE₀导波模式, 利用两束TE₀模的干涉从理论上实现了周期可调的亚波长光栅刻写. 分析了TE₀模式的色散关系, 刻写亚波长光栅的周期与激发光源、棱镜折射率、光刻胶薄膜厚度及折射率之间的关系. 用有限元方法数值模拟了金属薄膜、光刻胶薄膜和空气多层结构中TE₀导模的干涉场分布. 研究发现, 激发光源波长越短, TE₀ 模干涉刻写的亚波长光栅周期越小; 光刻胶越厚, 刻写的亚波长光栅周期越小; 高折射率光刻胶有利于更小周期亚波长光栅的刻写. 相较于表面等离子体干涉光刻, 基于TE₀ 模的干涉可在厚光刻胶条件下通过改变激发光源、棱镜折射率、光刻胶材料折射率、特别是光刻胶薄膜的厚度等多种方式实现对亚波长光栅周期的有效调控.     

Numerical simulation of optical bi-stability in antiferromagnetic sandwich structure

The magnetically optical bi-stability, a third-order nonlinear response, is investigated on an antiferromagnetic (AF) sandwich structure, where an AF film is sandwiched between two dielectric films. The configuration with the AF anisotropy axis and external static magnetic field both in the interfaces and normal to the incident plane is used. The incident wave is taken as a TE wave with its electric component transverse to the incident plane. We find that bistable switches can appear only in a finite frequency range and an incident angle range for a given regime of incident power, which means that there are the critical incident angle and frequency. The power threshold value for the bi-stability increases with the incident angle. In addition, the bi-stability also easily is modulated by the external magnetic field.     

真空热退火温度对单相Ag2O薄膜微结构和光学性质的影响

利用直流磁控反应溅射技术在玻璃衬底上沉积了单相Ag₂O薄膜,并采用真空热退火对单相Ag₂O薄膜在不同热退火温度 (T _{A) 下进行了1 h热处理.利用X射线衍射谱、扫描电子显微镜和分光光度计研究了 T A对单相Ag2O薄膜微结构和光学性质的影响.研究结果表明, T}A= 300 ℃ 时Ag₂O薄膜中开始出现Ag纳米颗粒,且随着 T _{A的升高薄膜中Ag的含量 关键词： 2}O薄膜')" href="#">Ag₂O薄膜 热退火温度 微结构 光学性质