A theorem on refractive index as a function of wavelength

A theorem upon refractive index as a function of wavelength is derived starting from the Taylor expansion around the origin of this function. Our result involves the above index, the group index, and the coefficient of material dispersion all extrapolated to zero wavelength.     

甲苯硝化物的折光率及介电波谱

介电波谱 (DS)用偶极及折射率作为探测器以测试介电物质的结构和反应过程。介电分析比较简单 ,并能得到其它方法不可能得到的结果。以 2 ,4 二硝基甲苯和 2 ,6 二硝基甲苯 (同分异构体 )为介电波谱分析的示例 ,得到了很好的结果。     

相干场作用下介质的探测谱及折射率谱的实验测量

利用改进的马赫－曾德尔干涉仪在实验上测出了相干场（５８９．６ｎｍ）作用下钠原子蒸０汽介质在５８９．０ｎｍ附近的探测谱和折射率谱,并针对拉曙以场驱动的四能经理论模型给出了相应的理论曲线,此项实验结果为验证原子的相干性理论及实现介质的无吸收、高折射率的可能性提供了可靠的实验依据。     

A flexible metamaterial with negative refractive index at visible wavelength

In this paper, we demonstrated a realization of a flexible metamaterial with negative refractive index operating at visible wavelength. With the help of Finite-Difference Time-Domain (FDTD) method, we could establish design rules for the metamaterial and analyze the characteristics of it. To this end, the fishnet structure with the unit cell size 185 nm by 240 nm was fabricated. Due to the polymer dielectric spacer between the metal-layers, the metamaterial is freestanding without base substrate and additional backside etching process.     

量子真空计量标准中的非极性稀薄气体折射率测量研究

为进一步提高真空量值的复现性和准确性,最新研究采用量子技术实现对真空量值的测量与表征.该方法利用Fabry-Perot谐振腔实现腔内气体折射率的精密测量,并反演出气体密度,进而获得对应的真空量值,其中气体折射率的测量是影响真空量值准确性的关键.本文基于第一性原理,利用从头计算理论计算了在已知压力和温度条件下的氦气折射率,给出腔内气体压力与折射率关系的表达式,并利用基于Fabry-Perot激光谐振腔的真空测量装置,通过双腔谐振激光拍频精确测量了充气前后谐振激光频率的变化,测出了氦气折射率,并分析了测量不确定度.将理论计算值与实验测量值进行了对比分析,得出了制约准确度提高的主要因素,并提出了修正方法.     

利用光子晶体测量透明液体折射率

设计了用反Opal结构光子晶体测量透明液体折射率的实验.根据布拉格公式推导了用反Opal光子晶体测量透明液体折射率的公式.利用紫外-可见分光光度计分别测得光子晶体处于空气和透明液体中的透射谱,由透射谱分别确定光子晶体处于2种介质中的禁带中心波长,将中心波长代入测量公式即可得到透明液体折射率.实验测量了水和甘油的折射率,得到了与公认值相吻合的结果.     

Refractive index change of f-aggregate centres as a function of temperature

The refractive index change of a KBr crystal containing F, M and R centres is given as a function of temperature. There are angular frequency values for which the change is constant.     

高功率微波在电离层中传播的折射率研究

 高功率微波在电离层中的传播特性主要由其折射率的变化决定，而高功率微波的大气折射率与相应传输层面的电子浓度有关。结合电离层电子浓度分布模型对电子浓度和大气折射率进行了数值模拟，对电离层折射率以及折射率垂直梯度相对于高度的变化特性进行了分析。结合射线描迹法对高功率微波波束传播高度、仰角和距离进行了修正，并在低功率微波下进行实验验证，证实修正值更接近实际值。     

Refractive index profiling across a candle flame using speckle techniques

Refractive index profiles have been obtained at different heights in the region above a candle flame both theoretically and experimentally by means of double and multiple exposure speckle photography. Improved fringe visibility has been achieved in the case of the multiple exposure technique giving rise to accurate measurement of the refractive index. Theoretical analysis shows that the resulting speckle pattern is equivalent to the ordinary pattern convolved with a function representing the effect of light deflection, while the interference pattern obtained is modulated by a background representing the autocorrelation function of the diffuser.     

Refractive index and material dispersion in relativistic electron optics

The refractive index and material dispersion associated with relativistic motion of electrons are calculated. Moreover, the wavelength dependence of refractive index is compared with the Sellmeier model for the index of refraction of lightwaves.     

利用旋转液体特性测量液体折射率

在XY-1型旋转液体实验仪的圆柱形容器底部加装了圆形平面镜,利用旋转液体的几何特性和折射定律,即可测量液体的折射率.     

Refractive index profiles of ion implanted waveguides in thulium sodium yttrium tungstate

Planar waveguides were first formed in thulium sodium yttrium tungstate (Tm:NaY(WO₄)₂) crystals by the implantation of MeV He, P and Ni ions with certain doses at room temperature, respectively. The refractive index profiles of the three ion implanted waveguides were found different to some extent. The present data show that He⁺ ion implanted waveguides in Tm:NaY(WO₄)₂ should be the typical barrier type one, while a combination of radiation damage and radiation enhanced diffusion may be responsible for the refractive index profiles of the MeV Ni⁺ and P⁺ ion implanted waveguides in Tm:NaY(WO₄)₂.     

测量光纤折射率分布还原算法的研究

用透射式微分干涉法测量光纤内部折射率分布,其原理是利用旋转检偏器对测量光束进行调制,从相位分布和光程分布中计算出折射率分布。其中,从光程分布中解算出折射率分布的算法是关键。讨论了该算法的数学模型,推导了测量公式,并对算法的稳定性和误差进行了分析。利用自行研制的系统对渐变折射率分布光纤进行实测,与在NR 9200光纤测量仪上的结果进行了比较,对主要误差源进行了分析和计算机模拟。实测和模拟计算结果表明,该算法原理正确,系统稳定,测量精度优于10-3,完全可以用来测量光纤折射率分布。     

Refractive index distribution measurements by means of spectrally-resolved white-light interferometry

A new procedure to measure the spatial distribution of the refractive index in transparent media is presented. It is based on the spectral analysis of optical interferograms obtained from a wide, continuous-spectrum light source. The method yields fairly high precision (up to 10^-8) in the measurements of local values of differential refractive index, Δn (Δn=n−n_ref), along a line in the sample. By means of a CCD TV-camera linked to a microcomputer, fast recording and automatic data processing are achieved. As an application, we present an experimental study of a thermal gradient in a liquid sample.     

大尺寸磷酸二氢钾晶体的折射率均一性研究

采用德国Trioptics公司生产的新一代全自动高精度折射率测量仪,测量了磷酸二氢钾(KDP)晶体不同部位的样品位于近紫外到近红外波段(0.253—1.530μm)内12个不同波长处的折射率,测量精度达到10-6量级.结果表明,大尺寸KDP晶体不同部位样品的折射率存在不均一性,靠近晶体恢复区的样品折射率小于晶体锥头区的样品折射率,偏差在10-5—10-4量级.研究发现,这种折射率不均一性与晶体不同部位的结晶质量存在差异有关.另外,将测量数据与其他文献中的数据进行对比.结果显示,所测试的样品数、波段宽度、测量点数量以及数据的精度均超过其他文献,结合测试条件分析了不同文献数据存在差异的原因.最后,使用最小二乘法拟合得到了KDP晶体较为可靠的Sellmeier方程.     

Study and investigation of long period grating as refractive index sensor

In this paper, we have investigated the response of long period grating (LPG) as refractive index sensor. The response has been studied for refractive index variation ranging from 1 to 1.45. In this work, we found that the sensing mechanism is based on two different aspects. First is the change of coupling power from the guided core mode to other co-propagating cladding modes and second is the wavelength shift of the peak resonant wavelengths from their original positions due the change of refractive index of the environmental (external) medium surrounding the cladding of the grating.     

Refractive index of two-level gas in quantized field of counterpropagating waves

An expression for the refractive index of a gas of two-level atoms in the quantized single-mode field of counterpropagating waves is calculated. It is shown that in the limit of large numbers of photons the result reproduces the quasiclassical result in only the case of standing wave where intensities of both waves are equal. Explanation of this “strange” situation where the abilities of quantum field theory turn to be more restricted than those of classical theory is given.     

Determination of the refractive index over a wide wavelength range through time-delay measurements of femtosecond pulses

We present a simple method to measure the refractive index dispersion over a broad wavelength range (0.6-1.6 μm). In a first step, the optical group indices are obtained by measuring the time-retardation of tunable 150 fs laser pulses within a sample relative to air. The refractive index dispersion is then calculated using a Sellmeier equation that describes the measured group index dispersion. We show that our experimental data agree with previously published results to within 2 × 10⁻⁴ for a 3 mm thick sample of fused silica and to within 3 × 10⁻³ for the index n₁ of a 2 mm thick crystal of the highly dispersive and anisotropic organic crystal 4-N,N-dimethylamino-4′-N′-methyl stilbazolium tosylate (DAST).     

光学材料折射率和色散的高精度测量技术研究

本文探讨了在一般精度的测角仪器上达到高精度测量折射率和色散的新原理和新方法,这些新原理和方法包括:光学角规补偿法测色散、直角照射法、自准封闭式最小偏向角法。通过实际大量的测量工作证明在1″测角仪(测角精度为3″)和测微望远镜上,上述原理方法都可以达到△n~±3×10~(-6),△(n_λ_1-n_λ_2)~±2×10~(-6)的精度。