Nonlinear optical response of Au and Ag nanoparticles doped polyvinylpyrrolidone thin films

Colloidal Au and colloidal Ag were prepared by chemical reaction method and the nonlinear optical properties of Au and Ag nanoparticles doped polyvinylpyrrolidone (PVP) composite films were investigated using Z-scan technique with 38 ps pulses at 532 nm. Open aperture Z-scan measurements indicated that both the Au/PVP and Ag/PVP composite films exhibited reverse saturable absorption. Nonlinear absorption coefficients and third-order nonlinear refractive indices were determined. The mechanisms accounting for the process of nonlinear refractions were analyzed and the figures of merit W and T of the Au/PVP and Ag/PVP composite films were evaluated.     

Au:TiO2和Au:Al2O3纳米颗粒复合膜的线性和非线性光学特性

主要从实验和理论两个方面,探讨了不同Au颗粒尺寸和不同基质对Au：TiO₂和Au：Al₂O₃复合膜线性和非线性光学性质的影响.用吸收光谱研究了Au颗粒尺寸和基质与Au复合膜表面等离子体共振带之间的关系;用皮秒Z扫描技术研究了共振和非共振情况下(激发光波长分别为532nm和1064nm),Au颗粒尺寸和基质与复合膜三阶非线性极化率的关系.基于表面等离子体共振理论和局域场增强理论对复合膜进行了分析,得到了不同Au颗粒大小和不同基质时Au复合膜的 关键词： 金属纳米颗粒 复合膜 三阶非线性 表面等离子体共振     

Enhanced nonlinear optical absorption of Au/SiO2 nano-composite thin films

Nano metal-particle dispersed glasses are the attractive candidates for nonlinear optical material applications.Au/SiO 2 nano-composite thin films with 3 vol% to 65 vol% Au are prepared by inductively coupled plasma sputtering.Au particles as perfect spheres with diameters between 10 nm and 30 nm are uniformly dispersed in the SiO 2 matrix.Optical absorption peaks due to the surface plasmon resonance of Au particles are observed.The absorption property is enhanced with the increase of Au content,showing a maximum value in the films with 37 vol% Au.The absorption curves of the Au/SiO 2 thin films with 3 vol% to 37 vol% Au accord well with the theoretical optical absorption spectra obtained from Mie resonance theory.Increasing Au content over 37 vol% results in the partial connection of Au particles,whereby the intensity of the absorption peak is weakened and ultimately replaced by the optical absorption of the bulk.The band gap decreases with Au content increasing from 3 vol% to 37 vol % but increases as Au content further increases.     

Multilayer Au/TiO2Composite Films with Ultrafast Third-Order Nonlinear Optical Properties

We report on the ultrafast third-order optical nonlinearity in multilayer Au/TiO2 composite films fabricated on quartz substrates by pulsed laser deposition technique. The linear optical properties of the films are determined and optical absorption peaks due to surface plasmon resonance of Au particles are observed at about 590hm. The third-order optical nonlinearities of the films are investigated by z-scan method using a femtosecond laser （50 fs） at the wavelength of 800 nm. The sample showed fast nonlinear optical responses with nonlinear absorption coefficient and nonlinear refractive index being -3.66 × 10^-10 m/W and -2.95 × 10^-17 m^2/W, respectively. The results also show that the nonlinear optical effects increase with the increasing Au concentration in the composite films.     

Synthesis and microstructure of metal oxide thin films containing metal nanoparticles by liquid phase deposition (LPD) method

Au nanoparticles dispersed SiO₂-TiO₂ composite films have been prepared by a novel wet process, Liquid Phase Deposition (LPD) method. The composite films were characterized by XRD, XPS, TEM, ICP, SEM and UV-VIS absorption spectroscopy. The results showed that the SiO₂-TiO₂ composite films containing Au^III and Au^I ionic species were co-deposited from a mixed solution of ammonium silicofluoride, ammonium hexafluorotitanate, boric acid and tetrachloroauric acid. The heat treatment induced the reduction of Au ions and formation of Au nanoparticles in the film. TEM observation revealed that the Au nanoparticles with 5-10 nm in diameter were found to be dispersed uniformly in the SiO₂-TiO₂ matrix. The optical absorption band due to the surface plasmon resonance of dispersed Au particles were observed at the wavelength of 550 nm and shifted toward longer wavelength with increasing heat treatment temperature. Received 28 November 2000     

Enhanced optical nonlinear absorption of graded Au--TiO2 composite films

This paper reports that single-layer and graded Au-TiO2 granular composite films with Au atom content 15%- 66% were prepared by using reactive co-sputtering technique. The third-order optical nonlinearity of single-layer and graded composite films was investigated by using s- and p-polarized Z-scans in femtosecond time scale. The nonlinear absorption coefficient βeff of single-layer Au-TiO2 films is measured to be -2.3×10^3-0.76×10^3 cm/GW with Au atom content 15%-66%. The βeff value of the 10-layer Au-TiO2 graded film is enhanced to be -2.1×10^4cm/GW calculated from p-polarized Z-scans, which is about ten times the maximum βeff of single-layer films. Broadened response in the wavelength region 730-860 nm of the enhanced optical nonlinearity of graded Au-TiO2 composite films was also investigated.     

Large third-order nonlinear optical susceptibility of Au-Al2O3 composite films near the resonant frequency

2 O₃ composite films with high Au concentrations (30%–60% in volume fraction) were prepared by reactive co-sputtering and post rapidly thermal annealing. The structure of the films and the size distributions of the Au nanoclusters were examined by TEM, and the third-order nonlinear optical susceptibility χ⁽³⁾ was measured by degenerated four-wave mixing using a 70-ps pulse laser at 532 nm. The maximum value of the χ⁽³⁾ was about 1.2×10^-6 esu in the annealed films and occurred at around 45% Au concentration. The figure of merit, χ⁽³⁾/α (α is the absorption coefficient), has a value of 7×10^-12 esu cm over a wide range of Au concentrations. Received: 23 July 1997     

LARGE AND EXTREMELY FAST THIRD-ORDER NON-LINEARITY OF Ag NANOPARTICLES EMBEDDED INTO A CsxO SEMICONDUCTOR MATRIX

The third-order optical nonlinearity of Ag-O-Cs thin films, where Ag nanoparticles are embedded into a Cs_xO semiconductor matrix, was measured by the femtosecond optical Kerr technique. The third-order nonlinear optical susceptibility, χ⁽³⁾, of the thin films was estimated to be 1.1×10^-9 esu at the incident wavelength of 820 nm. The response time, i.e. the full width at half-maximum of the Kerr signal, is as fast as 114 fs only. The intrinsic third-order optical nonlinearity can be attributed to the intraband transition of electrons from the occupied state near the Fermi level to the unoccupied state. It is suggested that such a nonlinearity is further enhanced by the local field effect that is present in the metallic nanoparticles composite thin films.     

Nonlinear optical properties of [（CH3）4N]Au（dmit）2 using Z-scan technique

The third-order optical nonlinearities of [（CH3）4N]Au（dmit）2 （dmit = 4,5-dithiolate-1,3-dithiole-2-thione） at 532 nm and 1064 nm are investigated using the Z-scan technique with pulses of picoseconds duration. The Z-scan spectra reveal a strong nonlinear absorption （reverse saturable absorption） and a negative nonlinear refraction at 532 nm. No nonlinear absorption is observed at 1064 nm. The molecular second-order hyperpolarizability γ for the [（CH3）4N]Au（dmit）2 molecule at 532nm is estimated to be as high as （2.1 ±0.1） × 10^-31 esu, which is nearly three times larger than that at 1064 nm. The mechanism responsible for the difference between the results is analysed. Nonlinear transmission measurements suggest that this material has potential applications in optical limiting.     

Studies on third-order nonlinear optical properties and reverse saturable absorption in polythiophene/poly (methylmethacrylate) composites

We report here the studies on third-order nonlinear optical properties of two novel polythiophene composite films investigated using the Z-scan technique. The measurements were carried out using a Q-switched, frequency doubled Nd:YAG laser producing 7 nanosecond laser pulses at 532 nm. Z-scan results reveal that the composite films exhibit self-defocusing nonlinearity. The real and imaginary parts of the third-order nonlinear optical susceptibility were of the order 10⁻¹² esu. The effective excited-state absorption cross section was found to be larger than the ground state absorption cross section, indicating that the operating nonlinear mechanism is reverse saturable absorption (RSA). The polythiophene composite films also exhibit good optical power limiting of the nanosecond laser pulses. The nonlinear optical parameters are found to increase on increasing the strength of the electron-donor group, indicating the dependence of χ ⁽³⁾ on the electron-donor/acceptor units of polythiophenes.     

Au/SiO2纳米复合薄膜的微结构及光吸收特性研究

用多靶磁控溅射技术制备了Au/SiO₂纳米多层薄膜.利用透射电子显微镜以及吸 收光谱对Au/SiO₂复合薄膜的微观结构、表面形貌及光学性能进行了表征和测试 .研究结果表明：单层Au/SiO₂薄膜中Au沉积时间小于10s时，分散在SiO_{2< /sub>中的Au颗粒随Au的沉积时间的延长而增大；当沉积时间超过10s后，Au颗粒的尺寸几乎 不随沉积时间变化，但Au颗粒的形状由网络状结构变为薄膜状结构.［Au(t1关键词： 尺寸效应 纳米复合薄膜 吸收光谱 有效媒质理论}     

Microstructure and optical absorption of Au-MgF2 nanoparticle cermet films

The microstructure and optical absorption of Au-MgF2 nanoparticle cermet films with different Au contents are studied. The microstructural analysis shows that the films are mainly composed of the amorphous MgF2 matrix with embedded fcc Au nanoparticles with a mean size of 9.8-21.4nm. Spectral analysis suggests that the surface plasma resonance （SPR） absorption peak of Au particles appears at λ=492-537nm. With increasing Au content, absorption peak intensity increases, profile narrows and location redshifts. Theoretical absorption spectra are calculated based on Maxwell-Garnett theory and compared with experimental spectra.     

CuO薄膜的三阶非线性光学特性研究

采用脉冲激光沉积技术在Si(100)和熔石英基片上制备了单相的CuO薄膜.通过X射线衍射仪,拉曼光谱仪,场发射扫描电镜和紫外可见光光度计对薄膜的结构,表面形貌和光学性质进行了表征. 场发射扫描电镜结果表明CuO薄膜中晶粒排列致密且分布均匀,其尺寸约为45nm.结合飞秒激光(800nm,50fs)和Z扫描方法测量了薄膜的三阶非线性光学特性,结果表明CuO薄膜具有超快的非线性光学响应且非线性折射率和非线性吸收系数均为负值,其大小分别为-3.96×10^-17 m^{2< 关键词： CuO薄膜 Z-扫描')" href="#">Z-扫描 三阶光学非线性}     

Ag:Bi2O3复合膜的线性和非线性光学性质

从实验和理论两个方面，探讨了金属Ag不同掺杂浓度对Ag:Bi₂O₃复合膜线性和非线性光学性质的影响. 用吸收光谱研究了Ag浓度与Ag:Bi₂O₃复合膜表面等离子体共振带之间的关系；用皮秒Z-扫描技术研究了共振和非共振情况下(激发光波长分别为532nm和1064nm)，金属Ag浓度与复合膜三阶非线性极化率的关系. 基于表面等离子体共振理论和局域场增强理论对复合膜进行了分析，得到了不同Ag浓度时Ag:Bi₂O₃复合膜的三阶非线性效应，研究了激发波长和金属浓度对复合膜线性和非线性光学性质的影响. 结果表明，等离子体共振增强和合适的金属掺杂浓度使得三阶极化率增强二个量级，在Ag浓度为35％左右和接近等离子体共振频率(相应吸收带位于560nm—622nm)的532nm激发时，χ⁽³⁾具有最大值2.4×10^-9esu. 关键词： 金属纳米颗粒 复合膜 三阶非线性 表面等离子体共振     

Au-BaTiO3复合薄膜的脉冲激光沉积制备及其非线性光学效应

利用脉冲激光沉积技术制备了掺杂金纳米颗粒的钛酸钡复合薄膜Au-BaTiO3,用高分辨透射电镜和X射线光电子能谱对薄膜进行了表征。从透射电镜照片可以看出,制备的样品中金颗粒大小约为2~3 nm,呈球形,均匀分布在载体介质中。X射线光电子能谱给出了Ba3d、Ti2p和Au4f电子芯能级结合能,结果表明载体介质是以BaTiO3的形式存在,而Au以金属的状态掺杂其中。330~800 nm范围的线性吸收谱表明样品中Au颗粒的共振吸收峰在500 nm附近。用单光束纵向扫描方法测量了样品的三阶非线性光学效应,使用的光源为调Q的YAG激光器,波长为532 nm,脉宽为10 ns,得到的非线性折射率和非线性吸收系数分别为-2.42×10-6esu和2.22×10-6m/W,表明了Au-BaTiO3复合薄膜有较大的非线性光学响应。     

Implantation as a tool for performing selective materials (application to solar energy conversion)

A selective solar material must absorb most of the solar spectrum, principally the visible light, and reflect the IR light.

Insulators are generally transparent in a wide part of the optical spectrum and the defects are revealed in these crystals by strong absorption bands. On the other hand, metals absorb much of the IR and near IR light and have a large reflection coefficient in the same region of the spectrum. In previous papers^1,2 it has been shown that metallic colloids, formed by precipitation of impurities in insulators, are responsible for a strong absorption band. Such metallic inclusions may be easily produced in most insulators by implantation. According to the nature of the implanted metal a selective absorption can be obtained. So a composite material (cermet) may be performed combining a colloidal absorption in the visible and a metallic reflection. We will discuss the different ways to achieve these properties using direct ion beam implantation.

Various cermets (LiF: Na, Au; MgO: Na, Au) have been studied as function of energy (0.1-1 MeV) and dose (10¹⁶-10¹⁷ ions/cm²). Colloids are completely developed by consecutive annealing.⁴

The modelization of these cermets requires a careful characterization by optical methods (spectrophotometry) and microscopic investigation (TEM, SEM, RBS, SIMS).⁷ These techniques are used to determine the filling factor and the concentration profile of metal in the insulating matrix.

With the help of the Maxwell-Garnett theory and using a single or multilayer model it is possible to suggest an interpretation of the optical properties.     

Optical and Conductivity Studies of Cr3+ Doped Polyvinyl Pyrrolidone Polymer Electrolytes

Abstract

Polymer electrolyte films of polyvinyl pyrrolidone (PVP) embedded with various concentrations of Cr³⁺ ions were prepared by a solution casting technique. The complexation between the Cr³⁺ ions and the polymer was confirmed by Fourier transform infrared (FTIR) spectroscopy and UV–vis spectroscopy. The electrical conductivity of the films was measured using an impedence analyzer in the frequency range of 42?Hz to 5?MHz at ambient temperature. It was observed that the conductivity increased with the increase in the Cr³⁺ ion concentration. UV–visible absorption spectra in the wavelength range of 200–800?nm were used to determine the direct and indirect optical energy band gaps and optical absorption edge. Both of the optical band gaps decreased with the increase in Cr³⁺ ion concentration. FTIR studies on pure and Cr³⁺ doped PVP polymer films revealed the vibrational changes that occurred due to the effect of the dopant Cr³⁺ ions in the polymer. Our results suggested that Cr³⁺, as a dopant, is a good choice to improve the electrical properties of PVP polymer electrolytes.     

Au/SiO2纳米多层薄膜的制备及其性质表征

利用多靶磁控溅射技术制备了Au/SiO₂纳米颗粒分散氧化物多层复合薄膜.研究了在保持Au单层颗粒膜沉积时间一定时薄膜厚度一定、变化SiO₂的沉积时间及SiO₂的沉积时间一定而改变薄膜厚度时，多层薄膜在薄膜厚度方向的微观结构对吸收光谱的影响.研究结果表明：具有纳米层状结构的Au/SiO₂多层薄膜在560 nm波长附近有明显的表面等离子共振吸收峰，吸收峰的强度随Au颗粒的浓度增加而增强，在Au颗粒浓度相同的情况下，复合薄膜 关键词： 2纳米复合薄膜')" href="#">Au/SiO₂纳米复合薄膜 多靶磁控溅射 吸收光谱 有效介质理论     

Ultrafast third-order optical nonlinearity of several sandwich-type phthalocyaninato and porphyrinato europium complexes

The third-order optical nonlinearity of two sandwich-type phthalocyaninato and porphyrinato europium com- plexes, including double- and triple-deckers （Eu[Pc（OC5H11）8]2, Eu2（Pc）（TPP）2, Pc=phthalocyanine, TPP=5, 10, 15, 20- tetraphenylporphyrinate）, was investigated by using the femtosecond time-resolved optical Kerr gate method at 830 nm wavelength. Their second-order hyperpolarizability is estimated to be 0.74× 10^-30esu and 3.0× 10^-3esu respectively. This exhibits an evident enhancement in comparison with 0.47×10^-30esu for one-decker Eu（Pc）（acac） （acac=acetylacetonate）, which is also measured under the same conditions. The enhancement is attributed to the introduction of lanthanide metal to the large π-conjugated system, intermacrocycle interaction and two-photon resonance etc.     

Dependence of intermediated noble metals on the optical and electrical properties of ITO/metal/ITO multilayers

Sn doped In₂O₃ (ITO) single layer and a sandwich structure of ITO/metal/ITO (IMI) multilayer films were deposited on a polycarbonate substrate using radio-frequency and direct-current magnetron sputtering process without substrate heating. The intermediated metal films in the IMI structure were Au and Cu films and the thickness of each layer in the IMI films was kept constant at 50 nm/10 nm/40 nm. In this study, the ITO/Au/ITO films show the lowest resistivity of 5.6 × 10⁻⁵ Ω cm.However the films show the lower optical transmission of 71% at 550 nm than that (81%) of as deposited ITO films. The ITO/Cu/ITO films show an optical transmittance of 54% and electrical resistivity of 1.5 × 10⁻⁴ Ω cm. Only the ITO/Au/ITO films showed the diffraction peaks in the XRD pattern. The figure of merit indicated that the ITO/Au/ITO films performed better in a transparent conducting electrode than in ITO single layer films and ITO/Cu/ITO films.