Large near resonance third order nonlinearity in GaN

We have studied third order nonlinearities, including two-photon absorption coefficient and nonlinear refractive index n ₂, of GaN in below bandgap ultraviolet (UV) wavelength regime by using UV femtosecond pulses. Two-photon absorption was investigated by demonstrating femtosecond UV pulsewidth autocorrelation in a GaN thin film while femtosecond Z-scan measurements revealed information for both n ₂ and . The distribution of n ₂ versus wavelength was found to be consistent with a model described by the quadratic Stark effect, which is the dominant factor contributed to the nonlinear refractive index near the bandgap. Large on the order of 10 cm/GW and large negative n ₂ with a magnitude on the order of several 10^–12 cm²/W were obtained. The at near mid-gap infrared (IR) wavelength was also found to be on the order of several cm/GW by using two-photon-type autocorrelations in a GaN thin film. Taking advantage of the large two-photon absorption at mid-gap wavelengths, we have demonstrated excellent image quality on two-photon confocal microscopy, including two-photon-scanning-photoluminescence imaging and two-photon optical-beam-induced current microscopy, on a GaN Hall measurement sample and an InGaN green light emitting diode.     

Pb1－xMnxSe薄膜的光学特性

采用分子束外延的方法在BaF₂(111)衬底上制备出了高质量的Pb_1-xMn_xSe(0≤x≤0.0681)薄膜.X射线衍射结果表明，Pb₁-xMn_xSe薄膜为立方相NaCl型结构，没有观察到MnSe相分离现象，薄膜的取向为平行于衬底(111)晶面.晶格常数随着Mn含量的增加逐渐减小，Mn含量由Vegard公式得到.通 关键词： 1-xMn_xSe外延薄膜')" href="#">Pb_1-xMn_xSe外延薄膜 透射光谱 带隙 折射率     

电离层与卫星通信

利用电子流体动力学方程和麦克斯韦方程组推导了等离子体的特征频率、折射率，并讨论了电磁波在等离子体中传播的基本条件，从而得出了卫星通信的基本电磁学条件．     

第八届亚洲物理奥林匹克竞赛中实验考题的分析

介绍了第八届亚洲物理奥林匹克竞赛中实验考题——"干涉法测量玻璃热膨胀系数和折射率温度系数"的内容、实验原理,并对实验的考试结果进行了分析.     

脉冲偏压电弧离子镀TiO2薄膜的力学与光学性能

用脉冲偏压电弧离子镀技术在玻璃基片上制备均匀透明的TiO₂薄膜.利用X射线衍射仪、原子力显微镜、扫描电子显微镜、紫外-可见透射光谱仪和纳米压痕仪等手段,对不同脉冲负偏压下合成薄膜的相结构、微观结构、表面形貌、力学和光学性能进行表征.结果表明，沉积态薄膜为非晶态.脉冲负偏压对薄膜性能有明显的影响.随偏压的增加，薄膜厚度、硬度和弹性模量均先增大后减小，前者峰值出现在100—200 V负偏压范围，后两者则在250—350V范围.300 V负偏压时薄膜硬度最高，薄膜达到原子级表面光滑度，均方 关键词： 2薄膜')" href="#">TiO₂薄膜 脉冲偏压电弧离子镀 硬度 折射率     

Bimetallic Silver-Gold Film Waveguide Surface Plasmon Resonance Sensor

It is desirable that a surface plasmon resonance (SPR) sensor is highly sensitive to binding interactions within the sensing region, generate evanescent fields with long penetration depths, and utilize a metal film that is very stable even in extreme environmental conditions. In this study, we present the first example of a wavelength-modulated waveguide SPR sensor with a bimetallic silver-gold film for surface plasmon excitation. The underlying silver yields better evanescent field enhancement of the sensing surface, while the overlying gold ensures that the stability of the metallic film is not compromised. It is shown experimentally that in terms of dλ/dn, the bimetallic film waveguide SPR configuration has a sensitivity of 1232 nm/RIU, greater than two times improvement from the 594 nm/RIU achievable with single gold film waveguide SPR sensor. The higher sensitivity, compact nature, and better evanescent field enhancement of this configuration provides the potential to biosensing applications.     

Determination of the refractive index of spherical erythrocytes of human blood in the range 0.3–1.2 µm

A proposed procedure for determining the spectral values of the refractive index of spherical erythrocytes of human blood is based on angular light scattering and the use (for one-time scattering) of a multiple regression equation. A theoretical study of the stability of the relationship between the light scattering indicatrix and the refractive index of erythrocytes toward possible variations of their microstructure parameters is performed in order to select the optimal angles. The precision of the proposed method and its sensitivity to indicatrix measurement uncertainties are estimated. __________ Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 382–386, May–June, 2007.     

A Method for Measuring the Three-Dimensional Refractive-Index Distribution of Single Cells Using Proximal Two-Beam Optical Tweezers and a Phase-Shifting Mach—Zehnder Interferometer

This paper describes a method for measuring the three-dimensional (3D) refractive-index distribution in a single cell. The method can be used to observe the distribution of cell components without fluorescence staining. The two-dimensional optical path length distributions from multiple directions are obtained by non-contact rotation of the cell. These optical path lengths are converted into the line integrals of the refractive index, and the 3D refractive-index distribution is reconstructed by means of computed tomography. The refractive-index distribution in a breast cancer cell can be measured using a phase-shifting Mach—Zehnder interferometer in conjunction with proximal two-beam optical tweezers.     

为2007年亚奥赛物理实验命题的体会

笔者被聘为2007年亚奥赛物理实验命题,经过半年多的努力终于将科研成果——激光测温合理地转换为一个奥赛实验试题——干涉法测量玻璃热膨胀系数和折射率温度系数,本文主要介绍了命题过程及体会.     

Imine‐linked porous organic polymers showing mesoporous microspheres architectures with tunable surface roughness

Different kinds of porous organic polymers (POPs) bearing 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BDP) fluorophores have been developed to generate singlet oxygen upon light illumination. Herein, four imine‐linked POPs were prepared by copolymerization of amine and aldehyde with different ratios of di‐aldehyde A1 and A2. The POPs were investigated by a combination of techniques such as solid ¹³C NMR, FTIR, and nitrogen absorption–desorption isotherms and electronic microscopy. The results demonstrated that these POPs were prone to form hierarchical porous architectures. Scanning electron microscopy and transmission electron microscopy images revealed that the spherical morphologies showed different roughness, that is, BDP‐POPs with more BDP aldehyde A2 presented rougher surface. Finally, these POPs were used to generate singlet oxygen (¹O₂) monitored by 1,3‐diphenylisobenzofuran and bioimaging in HeLa cells. Our results indicated that the ability to generate ¹O₂ is dependent on the amount of BDP. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 319–327