Homogeneous polymer blend microparticles with a tunable refractive index

We show that homogeneous polymer blend microparticles can be prepared in situ from droplets of dilute solution of codissolved polymers. Provided that the droplet of solution is small enough (<10 mum), solvent evaporation is rapid enough to inhibit phase separation. Thus the polymers that are being mixed need not be miscible, which greatly enhances the applicability of the technique. From analysis of two-dimensional Fraunhofer diffraction (angular scattering) patterns, we show that both the real and the imaginary parts of the refractive index can be tuned by adjustment of the relative weight fractions of polymers in solution.     

Temperature coefficient of the refractive index for PbTe film

Specimens of PbTe single film are deposited on Ge substrates by vacuum thermal evaporation.During the temperature range of 80–300 K,the transmittance of a PbTe film within 2–15μm is measured every 20 K by the Perkin Elmer Fourier transform infrared spectroscopy cryogenic testing system.Then,the relationship between the refractive index and wavelength within 7–12μm at different temperatures is received by the full spectrum inversion method fitting.It can be seen that the relationship conforms to the Cauchy formula,which can be fitted.Then,the relationship between the refractive index of the PbTe film and the temperature/wavelength can be expressed as n(λ,T)=5.82840-0.00304T+4.61458×10~(-6)T~2+8.00280∕λ~2+0.21544∕λ~4,which is obtained by the fitting method based on the Cauchy formula.Finally,the designed value obtained by the formula and the measured spectrum are compared to verify the accuracy of the formula.     

High frequency properties of a quasi-two-dimensional conductive film

The propagation of a monochromatic longitudinal acoustic wave along the low conductivity axis of a thin quasi-two-dimensional conductive film, in the absence of an external magnetic field, is studied theoretically. It is shown that under certain conditions the formation of both a standing ordinary wave (OAW) and an anomalous acoustic wave (AAW) is possible. The frequency dependence of the amplitudes of both waves is derived. For certain values of the characteristic parameters, the AAW in the film may be dominant. From the resonance conditions for the formation of standing OAW and AAW waves (especially the AAW), it is possible to obtain information about the electronic structure of the quasi-two-dimensional conductors, e.g. the corrugation parameter η or the relaxation properties of the charge carriers.     

利用泄漏波导测量低折射率薄膜的折射率和厚度

根据泄漏波导原理对K_9玻璃基板上的冰晶石薄膜进行折射率测量,达到的精度为1×10~(-4),与真实波导的情况相似。文中讨论了利用添加高折射率薄层减小待测薄膜的最小厚度的可能性。文中还利用光电方法观察反射光中暗条纹的方法判别波导的激发,并测出了冰晶石薄膜在4500到6500范围内的折射率。     

Effective refractive index and intermolecular forces associated with a phase of functional groups

Cases in which a functional groups form distinct phases are known in material science in general and specifically in polymer and surfactant sciences. To calculate the van der Waals forces associated with such phases there is a need to evaluate the refractive index of those phases. We expand and generalize a method to estimate the refractive index of such ‘functional group phase’ and discuss how to use the refractive indices to calculate the interaction energies associated with such functional group phases and thereby modify the total theoretically calculated van der Waals forces.     

Optical properties of aperiodic thin-layer structures: Effective refractive index

Simple analytical expressions for the effective refractive index of an aperiodic thin-layer structure have been obtained and analyzed. The expressions correctly describe the optical properties of the structure in a wide range of wavelengths. The optical properties that are general for the structures of this class have been established. The validity of the results is shown by a numerical experiment.     

Determination of thin film refractive index and thickness by means of film phase thickness

A new approach for determination of refractive index dispersion n(λ) (the real part of the complex refractive index) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are included in the calculations. Barium titanate thin films are investigated in the spectral region 0.38–0.78 μm and their n(λ) and d are calculated. The approach is validated using Swanepoel’s method and it is found to be applicable for relatively thin films when measured transmittance spectra have one minimum and one maximum only.      

Basic rules for the formation of a refractive index profile in planar polymer structures

The formation of a refractive index profile (RIP) in planar polymer structures with methyl methacrylate as the penetrant and a matrix composed of diallyl isophthalate with maleic anhydride is investigated experimentally. The effect of different factors on this process is studied: temperatures, diffusion times, diffusion boundary conditions, and ratios of the components of the system. Some data which give an idea of the optical characteristics of planar gradient-index lenses are presented. Zh. Tekh. Fiz. 67, 83–87 (April 1997)     

Dielectric supported ring-shaped metal disks on a metal film for ultrasensitive refractive index sensing

We experimentally report a magnetic plasmonic metamaterial, which is constructed with a metal ring-shaped disk array supported by a dielectric layer on a metal film for high sensitive refractive index sensing. An ultrasensitive refractive index sensitivity of about 1842?nm per refractive index unit is achieved through the reflection spectrum measurement. We attribute the high sensitivity to greatly enhanced electric field intensity and its large spatial overlapping with the surrounding medium to sense. The present plasmonic structure provides an effective way for high sensitive chip-based biochemical sensors and integrated devices.     

薄膜折射率非均匀性的测试(Ⅱ)

本文提出了根据多个周期的Δ、ψ轨迹来判别薄膜折射率非均匀性的原则。实验结果表明CeF_3、LaF_3、NdF_3薄膜基本上是均匀的。而热基板沉淀的Zns不但具有两侧表面层,还具有折射率渐增的中心层。文中还分析了用常规椭偏法测量ZnS等薄膜时误差的分布和大小。     

A method for measuring the complex refractive index and thickness of a thin metal film

A circularly polarized heterodyne light beam is incident on a thin metal film, causing successive reflections and refractions to occur at the two sides of the thin film. The phase difference between p- and s-polarizations of the multiple-beam interference signal can be measured accurately with an analyzer and heterodyne interferometry. The phase difference depends on the azimuth angle of the analyzer, the complex refractive index and the thickness of the thin metal film. The measured values of the phase differences under three different azimuth angles of the analyzer can be substituted into the special equations derived from Fresnels equations and multiple-beam interference. Hence, the complex refractive index and the thickness of the thin metal film can be estimated by using a personal computer with a numerical analysis technique. Because of its common-path optical configuration and its heterodyne interferometric phase measurement, this method has many merits, such as high stability against surrounding vibrations, high resolution and easy operation. PACS 78.66.Bz; 78.20.Ci; 07.60.Cy     

周期结构薄膜在折射率色散下反射区特性研究

周期性结构是光学薄膜设计的基本物理模型,给出了反射区中心波长的一般性条件,研究了在膜层材料存在折射率色散情况下,等厚周期结构和非等厚周期结构的薄膜反射区中心波长与带宽特性.研究结果表明:在等厚和非等厚周期结构中,考虑膜层材料折射率色散与忽略色散情况相比,中心波长向长波方向移动,反射级次与相对波数的线性关系偏离;在薄膜光学厚度一定的非等厚周期结构中,高折射率层光学厚度大于低折射率层时,反射级次与相对波数的线性关系偏离度高;非等厚周期结构薄膜的带宽在低反射级次上小于等厚周期结构,同时膜层的色散对反射带宽影响不大.     

溶胶-凝胶法制备高折射率TiO2薄膜

 采用溶胶- 凝胶法制备了TiO₂纳米晶溶胶,并以旋涂法（spin-coating）镀制了高折射率光学薄膜。借助光散射技术和透射电镜研究了溶胶的微结构。采用原子力显微镜、场发射扫描电镜、紫外-可见-近红外光谱仪、椭偏仪、漫反射吸收光谱及强激光辐照实验,对膜层的结构、光学性能及抗激光损伤性能进行了系统的表征。结果显示:纳米晶薄膜的折射率达到了1.9,而传统的溶胶-凝胶薄膜折射率只有1.6;同时纳米晶薄膜的抗激光损伤阈值与传统的溶胶-凝胶薄膜相差不大,在1 064 nm处分别为16.3 J/cm²(3 ns脉冲) 和16.6 J/cm²(3 ns脉冲);纳米晶溶胶薄膜可以在保持较高抗激光损伤阈值情况下,大幅度提高薄膜折射率。     

溶胶-凝胶法制备高折射率TiO2薄膜

采用溶胶- 凝胶法制备了TiO2纳米晶溶胶,并以旋涂法（spin-coating）镀制了高折射率光学薄膜。借助光散射技术和透射电镜研究了溶胶的微结构。采用原子力显微镜、场发射扫描电镜、紫外-可见-近红外光谱仪、椭偏仪、漫反射吸收光谱及强激光辐照实验,对膜层的结构、光学性能及抗激光损伤性能进行了系统的表征。结果显示:纳米晶薄膜的折射率达到了1.9,而传统的溶胶-凝胶薄膜折射率只有1.6;同时纳米晶薄膜的抗激光损伤阈值与传统的溶胶-凝胶薄膜相差不大,在1 064 nm处分别为16.3 J/cm2(3 ns脉冲) 和16.6 J/cm2(3 ns脉冲);纳米晶溶胶薄膜可以在保持较高抗激光损伤阈值情况下,大幅度提高薄膜折射率。     

Effective refractive index for determining ray propagation in an absorbing dielectric particle

The ray-tracing technique can be employed to simulate the scattering of light by a dielectric particle whose characteristic dimension is much larger than the incident wavelength. When a scattering particle is absorptive, a localized electromagnetic wave refracted into the scatterer is inhomogeneous, which requires the use of an effective refractive index to determine the propagation direction of the refracted ray. The effective refractive index for the first-order reflection–refraction event (i.e., the case for the ray-transmission from air into a particle) has been previously derived by the authors. In this study, we further develop recurrence formulae for the effective refractive indices associated with higher-order reflection–refraction events when the ray-transmission is from a particle to air. It is shown from the new formulae that effective refractive indices in this case depend upon ray history. Numerical results indicate that the real and imaginary parts of the effective refractive index are larger and smaller, respectively, than the real and imaginary parts of the inherent complex refractive index of an absorbing particle. Furthermore, if the particle faces associated with two sequential internal reflections are parallel to each other, the corresponding effective refractive indices are the same.     

Widely tunable long-period fiber grating with nm-thick higher refractive index film overlay

By introducing a four-layer step-index waveguide modeling, the characteristics of long-period fiber grating (LPFG) with an nm-thick film overlay, which has higher refractive index than that of fiber cladding are investigated in detail. The influence of both the overlay thickness and refractive index on the tuning ability of LPFG is analyzed. The numerical results demonstrate that spectral response of LPFG is divided into three distinct regions as the overlay deposition increases and the shift of resonant wavelength is drastic in some special thickness range. In conjunction with higher-order cladding mode coupling and fiber cladding etching, the sensitivity of LPFG to the overlay refractive index is enhanced significantly and over 120 nm resonant wavelength tunable range is achieved.     

光学薄膜折射率和厚度测试仪检定规程解读

简要介绍光学薄膜折射率和厚度测试仪检定规程的构成，被检测量仪器的技术指标、主要检定参数和检定方法等。该规程适用于光谱椭偏法测量光学薄膜折射率和厚度的仪器，在从事光学薄膜研究、生产和使用的单位具有广泛的应用前景。     

All organic DFB laser enhanced by intermediate high refractive index polymer layer

Performances of a distributed feedback (DFB) organic dye laser were enhanced by introducing an intermediate high refractive index layer of poly(N-vinylcarbazole) (PVCz) laminated between a glass substrate and a laser dye doped active polymer layer. The active layer is consisted of rhodamine 6G and cellulose acetate (CA). Introduction of an intermediate layer allows a single mode lasing. Slope efficiencies of 2.2 and 4.7% and thresholds of 0.3 and 0.14 mJ/cm²/pulse were measured for the waveguides with 1.7 and 3.4 μm active layers, respectively. Furthermore, permanent relief grating on an intermediate layer gave rise to the reduction of the threshold. With increasing in amplitude of the relief grating from 20 to 45 nm, lasing threshold was reduced from 0.18 to 0.04 mJ/cm²/pulse for the waveguide with 1.7 μm active layer. The slope efficiency increased from 3.5 to 4.2%.     

Positron annihilation studies of a conjugated polymer

Lineshapes of the Doppler broadened annihilation radiation (DBAR) of a conjugated polymer polydiacetylene, 4-butoxycarbonylmethylurethane (P-4BCMU), in its amorphous state, were measured over the temperature range of 30 to 190°C. A differential-scanning-calorimeter (DSC) was used to correlate the transition temperatures. The DBAR lineshapes show a distinct change during the structural transitions of the polymer. A two states trapping model is used to qualitatively describe the temperature dependence of the lineshape. The nature of formation of the trapped states of positrons above T_c, through the interplay of electronic structure/conformation change, is discussed.