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1.
The third-order optical nonlinearity of Ag-O-Cs thin films, where Ag nanoparticles are embedded into a CsxO 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.  相似文献   

2.
Laser induced crystallization of as-deposited amorphous Ge_2Sb_2Te_5 films   总被引:1,自引:0,他引:1  
Crystallization is induced by pulsed laser irradiation of as-deposited amorphous Ge_2Sb_2Te_5 films. Changes of the irradiated areas have been analyzed with the reflectivity contrast. As laser fluences increasing, the reflectivity contrast increases from 0%-2% to 14%-16%, which indicates the structure of asdeposited films transforms from amorphous to crystalline phases. The process of crystallization driven by the movement and rearrangement of atoms is described. And also the influence of the pulse duration on the threshold of crystallization is discussed, the results show that a lower threshold of crystallization can be produced for as-deposited films irradiated by the laser with short pulse duration. However, by the laser with long pulse duration, crystallization can only be formed with a higher threshold. The crystallization of films by irradiation of laser pulses is studied by Raman spectra.  相似文献   

3.
<正>The influence of laser conditioning on defects of HfO_2 monolayer films prepared by electron beam evaporation (EBE) is investigated utilizing the spot-size effect of the laser-induced damage.It is found that the laser-induced damage threshold of HfO_2 monolayer films can be increased by a factor of 1.3-1.6.It is also found that the defects with low threshold can be removed by laser conditioning and defects with higher threshold may be removed partially.  相似文献   

4.
The photodarkening effect in amorphous As2S3 films is studied.The optical absorption edge shifts to a lower energy after illumination ar the bandgap light of 514.5nm wavelength by an argon laser.The shift in well annealed films can be recovered by annealing at 180℃ for 1 h but in un-annealed films it is irreversible.In addition,it was found that the magnitude of photodarkening ΔE increased with the increase of illumination light intensity and illumination time.The reversibility of photodarkening in amorphous As2S3 films can be applied in optical memories.  相似文献   

5.
We investigate the laser damage behaviour of an electron-beam-deposited TiO2 monolayer at different process parameters. The optical properties, chemical composition, surface defects, absorption and laser-induced damage threshold (LIDT) of films are measured. It is found that TiO2 films with the minimum absorption and the highest LIDT can be fabricated using a TiO2 starting material after annealing. LIDT is mainly related to absorption and is influenced by the non-stoichiometric defects for TiO2 films. Surface defects show no evident effects on LIDT in this experiment.  相似文献   

6.
The principles of constructing optical devices on the basis of diffractive structures with a vanadium dioxide film for the control of radiation in the mid-IR range are analyzed. Methods are described for the practical implementation of such devices at λ=10.6 μm, and their response characteristics are calculated. It is shown that a contrast of 1:107 can be attained in diffractive optical elements, and the actuation time of the elements when switched on by an intense laser beam can be shortened to tens of nanoseconds. Zh. Tekh. Fiz. 69, 91–96 (November 1999)  相似文献   

7.
Nanometre-sized gold particles embedded in BaTiO3 composite thin films (Au/BaTiO3) were fabricated by the pulsed laser deposition technique. The films were grown on MgO (100) substrates at 700℃. The crystalline property of the films was studied with x-ray diffraction. X-ray photoelectron spectroscopy was used to check the Au composition and chemical nature for the deposited films. The absorption peak due to the surface plasmon resonance of Au particles was observed at the wavelength of about 570 nm, which increased as the metal particle size was increased. The nonlinear optical properties of the Au/BaTiO3 films were determined using the z-scan method at the wavelength of 532 nm, which was close to the resonant frequency. The real and imaginary parts of the third-order nonlinear susceptibility χ(3) at an Au concentration of about 6.7 at.% were determined to be 6.62×10-7 esu and -6.24×10-8 esu, respectively. The films showed a very large absorption, masking the nonlinear refraction effect at high metal concentrations.  相似文献   

8.
Bi2S3-xSex/poly(methyl methacrylate)(PMMA)nanocomposite films were prepared using microwave assisted synthesis with different compositions of x.Crystal structure,surface morphology,and optical properties were investigated to characterize the prepared nanocomposite films.The crystallinity and optical band gap of the prepared Bi2S3-xSex/PMMA were affected by x.The prepared samples showed a blue shift in the absorption edge.The laser power dependent nonlinear refraction and absorption of Bi2S3-xSex/PMMA nanocomposite films were investigated by using the Z-scan technique.The optical nonlinearity of the nanocomposite films exhibited switchover from negative nonlinear refraction to positive nonlinear refraction to negative nonlinear refraction effects,and from saturable absorption to reverse saturable absorption to saturable absorption with an increase and decrease in the composition.An interesting all-optical figure of merit was reported to assess the nanocomposite films for a practical device.It was calculated that the device all-figures of merit were based on the nonlinear response,which is important for the all-optical switching device.The results demonstrate that the optimized all-optical figures of merit can be achieved by adjusting the composition and input laser power,which can be used for the design of different all-photonic devices,and the results of nonlinear switching behavior can open new possibilities for using the nanocomposite films in laser Q-switching and mode-locking.  相似文献   

9.
We present a new experimental demonstration that the threshold points and shape of OB hysteresis curve in a four-level Rb atomic system inside an optical cavity were controllably changed by optical signals.Tuning the triggering optical signal to two different transitions of the atomic system we found that the OB threshold points shift toward different direction and at the same time the shape of the OB curve is also changed.For a given intensity of probe laser the OB system can be reliably inversed from its lower stable state to upper state under the triggering of a suitably tuned optical pulse signal (we named it up-controlling signal).More interesting, the inversed OB state does not drop to its initial lower stable state after the triggering pulse signal has passed, but moves to the upper branch of the initial OB curve and stably stays there until another optical signal tuned on other atomic transition (named down-controlling signal) coming.The result shows that there is the ability of information storage in the OB system.The experiments are reasonably explained with the change of cavity resonant condition resulting from the enhanced third-order nonlinearity in multilevel atomic system owing to atomic coherence.  相似文献   

10.
Sb-doped Ge Se2 chalcogenide thin films are prepared by the magnetron co-sputtering method.The linear optical properties of as-deposited films are derived by analyzing transmission spectra.The refractive index rises and the optical band gap decreases from 2.08 e V to 1.41 e V with increasing the Sb content.X-ray photoelectron spectra further confirm the formation of a covalent Sb–Se bond.The third-order nonlinear optical properties of thin films are investigated under femtosecond laser excitation at 800 nm.The results show that the third-order nonlinear optical properties are enhanced with increasing the concentration of Sb.The nonlinear refraction indices of these thin films are measured to be on the order of 10-18m2/W with a positive sign and the nonlinear absorption coefficients are obtained to be on the order of 10-10m/W.These excellent properties indicate that Sb-doped Ge–Se films have a good prospect in the applications of nonlinear optical devices.  相似文献   

11.
He-Ne散射光检测光学薄膜激光损伤阈值   总被引:3,自引:3,他引:0  
准确测定光学薄膜的激光损伤阈值可以衡量光学薄膜的抗激光损伤能力,测定损伤阈值的关键是准确地判定损伤的发生与否。建立了He-Ne散射光检测光学薄膜激光损伤阈值系统。通过测量同一样品点的He-Ne散射光能量变化来判断薄膜表面发生的损伤,并对制备的类金刚石薄膜与HfO2/SiO2反射膜进行了阈值测试。与等离子体闪光法的阈值测试结果进行比较,具有较好的一致性。分析表明:He-Ne散射光测试系统能有效地判断出激光诱导损伤,易于实现在线检测。  相似文献   

12.
The nonlinear optical properties of the isotropic phase of liquid crystals induced by nanosecond laser pulses are analyzed in the context of nonlinear multi-mode propagation in a liquid-crystal-cored fiber. The negative thermal density nonlinearity of the core gives rise to an intensity-dependent loss in the core-guided transmission and optical action. Experiments conducted with such liquid-crystal-cored fibers show that the optical limiting threshold for nanosecond laser pulses can be as low as 0.09 J/cm2, which is one of the lowest among known nonlinear optical materials and structures, including bulk liquid-crystal films.  相似文献   

13.
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.  相似文献   

14.
夏志林 《物理学报》2011,60(5):56804-056804
采用蒙特卡罗方法模拟了1064 nm,GW/cm2级脉冲激光辐照下,纳米尺度材料中电子迁移及加速过程.电子在激光场中迁移的过程涉及晶格散射、表面散射以及碰撞电离等作用.结果表明:材料的尺度小到一定程度后,表面散射作用主导电子散射过程,小尺寸限制效应表现明显,电子很难有效地吸收激光能量.研究结果对分析具有纳米尺度微结构材料的激光损伤行为提供了依据.同时,根据该小尺寸限制效应可以设计出具有新型纳米微结构的高激光损伤阈值薄膜. 关键词: 激光辐照 小尺度效应 电子加速 蒙特卡罗模拟  相似文献   

15.
The optical properties of CdSe/ZnS semiconductor nanocrystals with the core-shell structure are studied upon visible-laser excitation in a wide range of flux densities. It is demonstrated that the dimensional quantization effect is preserved in the films with a limiting high concentration of nanocrystals. A strong bathochromic shift of the absorption and luminescence peaks relative to the peak positions in the corresponding spectra of nanocrystals in films with a relatively low concentration of nanocrystals and solutions is caused by a high concentration of nanocrystals and the dipole moment related to the asymmetry of the nanoparticles. The shift is varied from 35 to 50 nm depending on the film thickness. The luminescence spectra of the films remain unchanged upon an increase in the laser intensity to 1 × 106 W/cm2. The laser action on the nanoparticle films is studied at intensities (5 × 106?1 × 109 W/cm2) higher than the damage threshold.  相似文献   

16.
准分子激光扫描消融淀积大尺寸超导薄膜   总被引:3,自引:0,他引:3       下载免费PDF全文
利用我们设计的一套光学变换传输系统实现了激光束在超导靶上一定范围内扫描消融来淀积高Tc超导薄膜。实验表明用这种激光扫描消融方法可使大尺寸超导薄膜的厚度均匀性得到较大的改善。我们采用激光扫描半径为9mm在12mm×33mm的Y-ZrO2基片上淀积出零电阻温度Tc≥90K,临界电流密度Jc(零磁场,77K)≥1×106A/cm2,薄膜c轴择优取向,厚度均匀性较好的YBa 关键词:  相似文献   

17.
利用电子束蒸发方法,在不同沉积温度(50~350℃)下制备了Sc2O3薄膜。分别用分光光度计,小角掠入射X射线衍射仪和轮廓仪测试了薄膜样品的光谱、微结构和表面粗糙度信息,并用薄膜分析软件Essential Macleod计算了Sc2O3薄膜的折射率和消光系数。结果表明:随着沉积温度升高,Sc2O3薄膜结晶程度增强,晶粒尺寸增大,且较高的沉积温度有利于获得较高的折射率。最后用355 nm,8 ns的三倍频Nd:YAG激光器测试了其激光损伤阈值(LIDT),最大值为2.6 J/cm2,且阈值与薄膜的消光系数、表面粗糙度、光学损耗均呈现相反的变化趋势。用光学显微镜和扫描电子显微镜表征了该薄膜的破坏形貌,详细分析了薄膜在不同激光能量作用下破坏的发展过程,以及Sc2O3薄膜在355 nm紫外激光作用下LIDT与制备工艺的关系,重点分析了355 nm激光作用下薄膜的破坏机理。  相似文献   

18.
《Current Applied Physics》2010,10(2):565-569
The polycrystalline Cu2ZnSnS4 (CZTS) thin films have been prepared by pulsed laser deposition (PLD) method at room temperature. The laser incident energy was varied from 1.0 at the interval of 0.5–3.0 J/cm2. The effect of laser incident energy on the structural, morphological and optical properties of CZTS thin films was studied by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and optical absorption. The studies reveal that an improvement in the structural, morphological and optical properties of CZTS thin films with increasing laser incident energy up to 2.5 J/cm2. However, when the laser incident energy was further increased to 3.0 J/cm2, leads to degrade the structural, morphological and optical properties of the CZTS thin films.  相似文献   

19.
The ablation process of thin copper films on fused silica by picosecond laser pulses is investigated. The ablation area is characterized using optical and scanning electron microscopy. The single-shot ablation threshold fluence for 40 ps laser pulses at 1053 nm has been determinated toF thres = 172 mJ/cm2. The ablation rate per pulse is measured as a function of intensity in the range of 5 × 109 to 2 × 1011 W/cm2 and changes from 80 to 250 nm with increasing intensity. The experimental ablation rate per pulse is compared to heat-flow calculations based on the two-temperature model for ultrafast laser heating. Possible applications of picosecond laser radiation for microstructuring of different materials are discussed.  相似文献   

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