SrBi2Ta2O9铁电薄膜的三阶非线性光学性能的研究

采用射频磁控溅射法在石英玻璃衬底上制备出均匀透明的SrBi2Ta2O9(SBT)薄膜,根据透射谱计算表明薄膜样品厚度为349nm,线性折射率为3.05.以锁模Nd:YAG激光器作为光源,利用Z-scan技术测定了薄膜的非线性光学性能.结果表明薄膜的非线性折射率n2＝2.56×10-8esu,非线性光吸收系数β＝3.93×10-4 esu,其三阶非线性极化率的实部和虚部分别为:Reχ(3)＝8.29×10-9 esu和Imχ(3)＝1.08×10-9 esu.     

Third-order nonlinear response of Ag/methyl orange composite thin films

The large third-order nonlinearities of metal nanocluster doped oxide matrix composite films have been investigated widely, but there is very little literature reporting third-order nonlinearity of metal nanoparticle doped azobenzene molecule thin films induced by picosecond laser pulses. This paper has investigated the third-order nonlinearity of colloidal Ag and methyl orange composite films using the Z-scan technique with 38 ps pulses at 532 nm apart from the surface plasma resonance frequency of composite film. Large and negative third-order nonlinearity was observed. The mechanism responsible for the process of nonlinear refraction was discussed in terms of the enhancement of the local field effect, which was confirmed by using the SERS technique. At the end, the figures of merit were evaluated and the results showed that this material would be valuable in the application of all-optical devices.     

Rh:BaTiO3 thin films with large nonlinear optical properties

We report the fabrication and the nonlinear optical properties of Rh-doped BaTiO3 thin films. The films were deposited on SrTiO3 (100) substrates by pulsed-laser deposition. The deposited Rh:BaTiO3 thin films were single phase and c-axis orientation investigated by x-ray diffraction. The films exhibited large nonlinear optical effects, which were determined using Z-scan technique at a wavelength of 532 nm with a laser duration of 10 ns. The real and imaginary parts of the third-order nonlinear susceptibility chi (3) were 5.71 x 10(-7) esu and 9.59 x 10(-8) esu, respectively. The value of Re chi (3) of Rh:BaTiO3 films is much larger than those of several representative nonlinear optical thin films. The results show that Rh:BaTiO3 thin films have great potential applications for nonlinear optical devices.     

Azobenzenes for photonic network applications: Third-order nonlinear optical properties

We review the third-order nonlinear performance of pseudo-stilbene type azobenzenes with an eye to application in ultrafast optical signal processing. We discuss mechanisms responsible for the nonlinear response of the azobenzenes. By aggregating experimental data and theoretical trends reported in the literature, we identify five characteristic regions of optical nonlinear response. Analyzed with respect to Stegeman figures of merit, pseudo-stilbene type azobenzenes show promise for ultrafast optical signal processing in two spectral regions, one lying between the main and two-photon absorption resonances, and the other for wavelengths longer than the two-photon absorption resonance. © 2001 Kluwer Academic Publishers     

Structural and optical properties of GaGeTe thin films

Smooth and pinhole-free thin films of Ga₅Ge₁₉Te₇₆ have been obtained by vacuum evaporation. The as-deposited films are amorphous. Thermal annealing at 222°C leads to an amorphous-to-crystalline transition. A maximum contrast of 30% in reflectivity (measured at 1 µm) has been obtained on phase transition from amorphous to crystalline state. The optical constants and the bandgap are reported.     

Nonlinear optical and acoustic properties of thin films

The nonlinear optical and acoustic properties of thin films have been studied experimentally. The following nonlinear effects have been investigated: acoustic wave generation; stimulated light scattering due to acousto-optic interaction; and the influence of excitation conditions, film structure, and film composition on the above effects.     

Electrical and optical properties of TiN thin films

TiN thin films have been grown by reactive magnetron sputtering. It has been shown that an Ohmic contact to TiN thin-film can be made from indium. The TiN thin films have been shown to be n-type semiconductors with a carrier concentration of 2.88 × 10²² cm^?3 and resistivity of ρ = 0.4 Ω cm at room temperature. The activation energy for conduction in the TiN films at temperatures in the range 295 K < T < 420 K is 0.15 eV. The optical properties of the TiN thin films have been investigated. The material of the TiN thin films has been shown to be a direct gap semiconductor with a band gap E _g = 3.4 eV.     

Third-order optical nonlinearities in anatase and rutile TiO2 thin films

Titanium dioxide (TiO₂) films have been fabricated on fused quartz and Si(001) substrates by pulsed laser deposition technique and the single-phase anatase and rutile films were obtained under the optimal conditions. The surface images and optical transmission spectra were investigated by scanning electron microscopy and double beam spectrophotometer, respectively. The values of optical band-gap and linear refractive index of the anatase and rutile films were determined. The optical nonlinearities of the films were measured by Z-scan method using a femtosecond laser (50 fs) at the wavelength of 800 nm. Through the open-aperture and closed-aperture Z-scan measurements, the real and imaginary parts of the third-order nonlinear optical susceptibility were calculated and the results show that the anatase phase TiO₂ films exhibit larger nonlinear refractive effects compared with rutile phase. The figure of merit, T, defined by T = βλ/n₂, was calculated to be 0.8 for anatase films, meeting the requirement of T < 1 and showing potential applications in all-optical switching devices.     

Third-order optical nonlinear absorption in Bi1.95La1.05TiNbO9 thin films

Single phase Bi_1.95La_1.05TiNbO₉ (LBTN-1.05) thin films with a layered aurivillius structure have been fabricated on fused silica substrates by pulsed laser deposition at 700 °C. The X-ray diffraction pattern revealed that the films are single-phase aurivillius. The band gap, linear refractive index and linear absorption coefficient were obtained by optical transmittance measurements. The film exhibits a high transmittance (> 70%) in visible-infrared region and the dispersion relation of the refractive index vs. wavelength follows the single electronic oscillator model. The nonlinear optical absorption property of the film was determined by the single beam Z-scan method using 800 nm with a duration of 100 fs. A large positive nonlinear absorption coefficient β = 5.95 × 10^− 8 m/W was determined experimentally. The results showed that the LBTN-1.05 is a promising material for applications in absorbing-type optical devices.     

Intrinsic optical and structural properties of SrS thin films

SrS thin films were deposited by electron beam evaporation on heated silica substrates. The optical properties of the layers – complex refractive index and optical band gap –were derived from optical transmission spectra, measured by means of UV-VIS-NIR spectrophotometry. The influence of post-deposition annealing by rapid thermal processing (RTP) was studied. X-ray powder diffraction (XRD) was used to study the film crystal structure and preferential orientation.     

Electrical and optical properties of molybdenum trioxide thin films

Infrared spectra of vacuum-deposited molybdenum trioxide thin films have been studied. The variation of electrical conductivity with temperature for different thicknesses of films has been investigated. Electrical conductivity of the films as a function of time of UV irradiation was found to increase initially, then decreased rapidly and reached a steady value. It increased and reached a steady value with time when irradiation was cut-off.     

The optical properties of zirconium diboride thin films

The optical properties of evaporated thin films of zirconium diboride were investigated from 4.1 to 11.3 eV. The optical constants were determined by reflectance measurements made at near-normal and oblique angles of incidence. The existence and energy of interband transitions and the plasma frequency are inferred from these results.     

The optical properties of sprayed CdS thin films

In the study presented in this paper we attempted to interpret the reflectance and the transmittance of sprayed CdS films. Assuming a model based on multilayer film theory we showed that sprayed CdS film is a combination of multilayer stacks of crystallites and gaseous inclusions.     

HfO2薄膜的制备与光学性能

采用射频磁控反应溅射法，以高纯热压HfO2陶瓷为靶材，在Si衬底上成功制备出HfO2薄膜。系统研究了工艺参数对薄膜沉积速率的影响规律，并对薄膜的光学性能进行了研究。结果表明，射频功率对薄膜沉积速率的影响最为明显，O2／Ar流量比和衬底温度对沉积速率的作用不明显，所制备薄膜的折射率较高在近红外波段趋于1．95，在500-1650nm波段范围内薄膜几乎无吸收，透过率较高。     

CuInS2薄膜的制备及光学特性

真空共蒸发在玻璃衬底上制备CuInS2薄膜.研究不同Cu、In、S元素配比、不同热处理条件对薄膜的结构、化学计量比及光学性能的影响.实验结果给出:在元素配比中S的原子比x选择极为重要(实验选0.2≤x≤2),本实验Cu、In、S最佳原子比为1:0.1:1.2.用x(Cu).x(In):x(S)=1:0.1:1.2原子比...     

Structural and optical properties of GaN-based nanocrystalline thin films

We study the effect of annealing on structure, morphology and optical properties of nanocrystalline films of GaN, GaN:O and GaN:Mn prepared by ion assisted deposition on silicon, quartz and glassy carbon substrates. Blisters and holes having diameters proportional with the thickness of the film were observed in GaN:O deposited on silicon and glassy carbon. The Mn excess in GaN:Mn turns through annealing into Mn_xN_y islands. The degree of short- and intermediate-range order in the films was investigated by micro-Raman spectroscopy, extending to about 3 nm for gallium oxynitride films annealed to 973 K and to more than 10 nm in GaN samples. A diminished oxygen content following the annealing procedures on GaN:O samples is noticed from the reduced intensity of the oxygen mode at 1000 cm^− 1 in the Raman spectra. This observation is supported with X-ray photoemission spectroscopy measurements. The presence of oxygen at concentrations above 15at.% in the films leads to an abrupt nanocrystalline-amorphous transition.     

Electronic transport and optical properties of thin oxide films

In this work, we present optical characterization of films of two transparent conductive oxides (ITO: indium tin oxide and ZnO: zinc oxide) including absorption coefficient and optical gap energy. We have also investigated the transport properties of ITO and ZnO films through measurements of electrical conductivity and thermoelectric power versus temperature. These measurements enabled us to investigate conduction mechanisms for metal-nonmetal transitions. Undoped ZnO thin films show a metal-semiconductor transition at temperatures beyond 350 K. We have conducted a similar study on ITO films where we demonstrated, for the first time, the existence of a conductivity transition below 400 K, which indicates a high absolute thermoelectric power at temperatures above the transition temperature.     

Structure and optical properties of CuGaSe2 thin films

The structure and optical properties of vacuum-deposited films of CuGaSe₂ were studied at various substrate temperatures. Stoichiometric films could be obtained at substrate temperatures as low as 450 K. Epitaxial growth was observed on single-crystal NaCl substrates at temperatures above 500 K. The optical transition energies obtained at 1.68, 1.78 and 1.92 eV were in good agreement with previous results.