Third harmonic generation of laser radiation in Fe- and Zn-doped polyvinylpyrrolidone

The results of third-order nonlinear susceptibilities studies of Fe- and Zn-doped polyvinylpyrrolidone (PVP) aqueous solution in processes of third harmonic generation of Nd:YAG laser radiation are presented. Nonlinear susceptibilities of PVP:Fe and PVP:Zn were calculated to be 5×10^-13 esu and 3×10^-13 esu respectively. Third harmonic conversion efficiencies in these metallocomplexes were measured to be 8×10^-7 and 5×10^-7 respectively. The Z-scan method was applied to determine Kerr effect influence on frequency conversion process. The value of nonlinear refractive index of PVP:Fe at the wavelength of λ = 1064 nm was measured to be n ₂ = - 6.7×10^-13 esu. Received 30 November 2001 / Received in final form 27 March 2002 Published online 28 June 2002     

三-α-(2,4-二甲基-3-戊氧基)溴硼亚酞菁的三阶非线性光学性质研究

应用Z扫描技术，在波长为532nm、脉宽为8ns条件下，对一种新型亚酞菁配合物三-α-(2,4-二甲基-3-戊氧基)溴硼亚酞菁的三阶非线性光学特性进行了研究，结果发现，该新化合物有较强的反饱和吸收(β=3.7×10^-10 m/W)效应和非线性自聚焦折射效应(n₂=7.2×10^-11esu)，其三阶非线性极化率χ⁽³⁾=1.1×10^-11esu.分析了溴硼亚酞菁配合物特殊的锥形分子结构和重原子溴的轴向配位等因素对其三阶非线性光学性质的重要影响. 关键词： 亚酞菁 Z扫描 三阶光学非线性     

Spectral characteristics and nonlinear studies of methyl violet 2B dye in liquid and solid media

Solid-state dye-doped polymers are attractive alternatives to the conventional liquid-dye solutions. In this paper, the spectral characteristics and nonlinear properties of the dye Methyl violet 2B has been studied. The third-order nonlinear optical properties of Methyl violet 2B dye in ethanol and a dye-doped polymer film were measured by the Z-scan technique. This material exhibits a negative optical nonlinearity. The dye exhibited a nonlinear refractive coefficient (n ₂ = ?4.14 × 10^?7 and ?4.291 × 10^?7 cm²/W in liquid and solid media, respectively), nonlinear absorption coefficient (β = ?4.634 × 10^?3 and ?4.66 × 10^?3 cm/W in liquid and solid media, respectively), and susceptibility (χ⁽³⁾ = 1.88 × 10^?5 and 1.963 × 10^?5 esu in liquid and solid media, respectively). These results show that Methyl violet 2B dye has potential applications in nonlinear optics.     

Studies of third-order nonlinear optical properties of C60 by the optical Kerr effect

60 at 1.064 μm is determined by the optical Kerr effect in toluene solution. Values of -6.5×10^-33 esu and 2.0×10^-32 esu for the real and imaginary parts of γ, respectively, are obtained. Based on the experimental results and symmetry constraint, it is concluded that a three-level model is not adequate to describe the third-order nonlinearity of C₆₀. It is also inferred that the non-resonant γ of C₆₀ should be positive in sign, which is in agreement with reported off-resonant measurements of γ of C₆₀ by third-harmonic generation. Received: 3 September 1997/Revised version: 1 December 1997     

Effect of peripheral ligands on the optical limiting property of homoleptic sandwich-type rare earth metal diphthalocyanines

The optical limiting property of sandwich-type rare earth metal diphthalocyanines, Eu[Pc(R)₈]₂[R=n-C₇H₁₅,OC₅H₁₁], was investigated via fluence-dependent transmittance measurements. The measurements were performed using collimated 10-ns pulses generated from a frequency-doubled Nd:YAG laser at 532-nm wavelength. The results demonstrated that Eu[Pc(OC₅H₁₁)₈]₂ exhibited better optical limiting behavior than Eu[Pc(C₇H₁₅)₈]₂. This is attributed to the enhanced delocalization of the π-conjugated system in Eu[Pc(OC₅H₁₁)₈]₂ because of the stronger electron-donating ability of alkoxy relative to that of alkyl. Received: 4 May 2001 / Accepted: 10 August 2001 / Published online: 17 October 2001     

Enhancement of third-order nonlinearity in Ag-nanoparticles-contained chalcohalide glasses

Ag-nanoparticles were embedded in 56GeS₂?C24Ga₂S₃?C20KBr chalcohalide glass with average size varying from 100 to 300 nm. A large femtosecond optical Kerr effect indicated an enhancement of third-order optical nonlinearity due to Ag-nanoparticles observed by AFM images. Among these Ag-nanoparticles-embedded chalcohalide glass samples, the sample (c) with the second largest implanting dose 1 × 10¹⁷ ions/cm² showed the largest value of ??⁽³⁾ 5.34 × 10^?13 esu, which was ten times larger than that of the substrate. The nonlinear relation between the implanted dose and third-order optical nonlinearity is strongly related to the intrinsic local field and Ag-nanoparticles interaction in the glasses.     

Closed loops theory on the third-order nonlinear optical property of α- and β- isomers of [M8O26]4−: a TDDFT study

The third-order nonlinear optical (NLO) property of the α- and β- isomers of [Mo₈O₂₆]^4? polyoxometallate ion were studied by DFT/TDDFT method. The second static hyperpolarisabilities, γ_iiii, γ_iijj and γ_mean were calculated by finite-field method as an extension of the usual DFT run, and the results suggest that without any ligands coordinated, the two isomer molecules in high symmetry own modestly large γ values (γ_mean ～5×10^?32esu, 3×10^?32esu, respectively), and the electronic properties of the two isomers were also studied by DFT method for the discussion of the origination of the NLO response, especially the unique effect of the molecular orbital ‘closed loops' on the NLO response.     

Anisotropic giant magnetoresistance originating from the π-d interaction in a molecule

We synthesized TPP[Fe^III(Pc)(CN)₂]₂, PTMA_x[Fe^III(Pc)(CN)₂]·y(MeCN), and PXX [Fe^III(Pc)(CN)₂], a new series of charge-transfer salts containing the axially-substituted phthalocyanine (Pc), [Fe^III(Pc)(CN)₂]⁻. In this molecular unit, the π conduction electron derived from the Pc-ring coexists with the d electron which is a potential source of a local magnetic moment. Therefore various phenomena associated with the interplay between local magnetic moments and conduction electrons are expected. We observed the giant negative magnetoresistance (GNMR) in all the three salts. The GNMR is highly anisotropic for the magnetic-field direction, and reflects the g-tensor anisotropy of the local magnetic moment in the [Fe^III(Pc)(CN)₂]⁻ unit. This indicates that the GNMR in these salts originates from the strong π-d interaction in the [Fe^III(Pc)(CN)₂]⁻ unit.     

使用基团理论计算KB5O8·4H2O晶体的倍频系数

本文使用基团理论计算KB₅O₈·4HO₂O(简称KB5)晶体的倍频系数,得到d₃₁=2.61×10^-10esu,d₃₂=007×10^-10esu,d₃₃=3.26×10^-10esu,与实验值符合较好。计算结果表明:氢键对KB5晶体的倍频系数有影响。本文还分析了KB5晶体倍频系数小的起因,除去[B₅O₆(OH)₄]^-1基团的微观倍频系数小外,还在于基团的空间排列方式不利,导至最大的微观倍频系数X₁₂₃相互抵消。最后,本文提出了在含四配位硼原子的硼氧化合物中寻找倍频新材料的结构判据。 关键词：     

Optical and structural characterization of iron oxide and cobalt oxide thin films at 800 nm

We report on optical and structural properties of α-Fe₂O₃ and Co₃O₄ thin films, grown by direct oxidation of pure metal films deposited on soda-lime glass. Structural characteristics and morphology of the films were investigated by X-ray diffraction, atomic force microscopy, and scanning electron microscopy. Linear optical absorption, and linear refraction as well as nonlinear optical properties were investigated. The third-order optical susceptibilities were measured applying the Thermally managed Z-scan technique using a Ti: sapphire laser (150 fs; 800 nm). The results obtained for the Co₃O₄ film were \( \text{Re} \chi^{\left( 3 \right)} \) = ?(5.7 ± 2.4) ×10^?9 esu and \( \text{Im} \chi^{(3)} \) = ?(1.8 ± 0.2) ×10^?8 esu while for the α-Fe₂O₃ film we determined \( \text{Re} \chi^{(3)} \) = +(6.6 ± 2.4) ×10^?10 esu and \( \text{Im} \chi^{(3)} \) = +(2.2 ± 0.4) ×10^?10 esu.     

Nonlinear optical properties of Cr<Superscript>3+</Superscript>-doped laser crystals

The nonlinear optical properties in six Cr³⁺-doped laser crystals LiCaAlF₆, LiSrGaAlF₆, Gd₃Ga₅O₁₂, Gd₃Sc₂Ga₃O₁₂, LaMgAl₁₁O₁₉ and Alexandrite are investigated with the help of the Z-Scan technique at λ = 532 nm in the CW regime. The data reported here include particularly the excited state absorption cross section and the third-order nonlinear susceptibilities. It is found that the three first systems only exhibit both refractive and absorptive nonlinear effects, whereas the three others have only absorptive effects. Gd₃Ga₅O₁₂ shows the best nonlinear potentialities. The excited state absorption cross section corresponding mainly to the ⁴T₂ →   ⁴T₁ transition is found to be ranging between 8.9 × 10⁻²² cm² in LiSGaF and 3.1 × 10⁻²⁰ cm² in LaMgAl₁₁O₁₉. The calculated ratio of the third order nonlinear susceptibility to the ground state absorption coefficient is found to be largest in GGG with a value of 146 × 10⁻⁶ esu.cm and smallest in Alexandrite (0.6 × 10⁻⁶ esu.cm).     

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}     

Optical Nonlinearity of Emerging ZrS2 and HfS2 Semiconductors

Compatible with existing processing technology, chemical vapor deposition method is used to synthesize ZrS₂ and HfS₂ films a a large scale. The nonlinear optical properties are characterized by Z-scan measurement with femtosecond pulses at 800 nm. The results show that saturable absorption happens in ZrS₂ owing to the larger ground state absorption than the excited state absorption, while reverse saturable absorption appears in HfS₂ due to the two-photon absorption. The figure of merit values of ZrS₂ (≈4.30 ± 0.12 × 10⁻¹⁵ esu cm) and HfS₂ (≈6.0 ± 1.4 × 10⁻¹⁵ esu cm) are much larger than those of MoS₂ and graphene in ultrafast nonlinear optical performance at the wavelength of 800 nm.     

Large optical nonlinearity in CaCu<Subscript>3</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12</Subscript> thin films

CaCu₃Ti₄O₁₂ (CCTO) thin films were successfully prepared on LaAlO₃ substrates by pulsed laser deposition technique. We measured the nonlinear optical susceptibility of the thin films using Z-scan method at a wavelength of 532 nm with pulse durations of 25 ps and 7 ns. The large values of the third-order nonlinear optical susceptibility, χ ⁽³⁾, of the CCTO film were obtained to be 2.79×10⁻⁸ esu and 3.30×10⁻⁶ esu in picosecond and nanosecond time regimes, respectively, which are among the best results of some representative nonlinear optical materials. The origin of optical nonlinearity of CCTO films was discussed. The results indicate that the CCTO films on LaAlO₃ substrates are promising candidate materials for applications in nonlinear optical devices.     

Investigation of third-order optical nonlinearity in KBe2BO3F2 crystal by Z-scan

The third-order optical nonlinearity of deep-ultraviolet (DUV) nonlinear optical (NLO) crystal KBe₂BO₃F₂ (KBBF) was investigated using single-beam Z-scan technique for the first time. The Z-scans were performed on a c-cut KBBF crystal and a KBBF prism-coupling device (PCD) with picosecond pulses at 355?nm. No two-photon absorption was observed in the experiment. The measured nonlinear refraction index n ₂ showed positive signs, indicating self-focusing Kerr effects. The n ₂ values were estimated to be (1.75±0.35)×10^?15?cm²/W with the c-cut sample and (1.85±0.37)×10^?15?cm²/W with the PCD, corresponding to the third-order nonlinear optical susceptibilities $\chi_{\mathrm{eff}}^{(3)}$ of (0.99±0.20)×10^?13?esu and (0.94±0.19)×10^?13?esu, respectively. The results are expected to promote the investigation of frequency conversion processes with ultra-short laser in KBBF crystal.     

一种侧链共轭聚噻吩衍生物薄膜的三阶非线性光学响应

合成了一种侧链共轭的聚噻吩衍生物聚3-（5′辛基-噻吩乙烯基）噻吩（POTVTh）,并通过溶液旋涂制备了聚合物薄膜.吸收光谱显示该聚合物薄膜具有较小的禁带宽度和宽的光谱响应.采用Z扫描技术在800 nm下用飞秒激光器研究了该聚合物薄膜的三阶非线性光学特性,非线性吸收系数为5.63×10^-7cm/W,非线性折射率为-6.38×10^-11 cm²/W,三阶非线性极化率为4.21×10^-9esu,比侧链未共轭的 关键词： 聚噻吩衍生物 侧链共轭 三阶非线性极化率 非线性折射率     

Influence of iodine on the electrical properties of magnesium phthalocyanines thin film devices

The influence of iodine on the electrical properties of sandwich structures of magnesium phthalocyanine (Mg Pc) thin films with gold and aluminium electrodes has been investigated. The various electrical properties and different electrical parameters of the iodine-doped Mg Pc thin film devices have been estimated and compared with the values of normal Mg Pc devices from the analysis of the current-voltage characteristics. Generally samples showed an asymmetric conductivity both under forward and reverse bias. From our study we found that iodine doped Mg Pc films showed an enhanced electrical conductivity of nearly ten times that of typical Mg Pc. At low voltages the films showed an ohmic conduction with a hole concentration of P₀ = 6.34 × 10¹⁸ m⁻³ and hole mobility μ = 9.16 × 10⁻⁵ m ² V⁻¹ s⁻¹, whereas at higher voltage levels the conduction is dominated by space charged limited conduction (SCLC) with a discrete trapping level of 1.33 × 10²² m⁻³ at 0.63 eV above the valance band edge. The ratio of the free charges to trapped charges (trapping factor) for the doped samples was found to be 1.07 × 10⁻⁷. Furthermore the reverse conduction mechanisms have also been investigated. From the current limitations in the reverse condition a strong rectifying behaviour was evident which was attributed to Poole-Frankel emission with a field-lowering coefficient of value 2.24 × 10⁻⁵ eV m^1/2 V^−1/2.     

Na2SbF5晶体倍频系数的理论计算

本文使用阴离子基团理论计算了Na₂SbF₅晶体的倍频系数,得到d₁₂₃=4.48×10^-10esu,与实验值符合较好。计算结果表明,阴离子基团中孤对电子的存在有利于产生大的倍频效应。本文还分析了Na₂SbF₅晶体倍频系数小的原因:尽管(SbF₅)^2-基团存在孤对电子可以对晶体倍频系数有较大贡献,但孤对电子能级的相对位置对其倍频系数有不利影响,从而导致它的倍频系数d₁₂₃较小。 关键词：     

Te/TeO2-SiO2复合薄膜的吸收和非线性光学特性研究

应用分光光度计测量Te/TeO₂-SiO₂复合薄膜的透射光谱和吸收光谱, 在480nm附近观察到Te颗粒引起的等离子体共振吸收峰; 采用Z扫描技术研究了共振(激发波长为532 nm)和非共振情况下(激发波长1064 nm) 不同电位制备薄膜的Te颗粒状态与复合薄膜的三阶非线性极化率的关系. 基于有效介质理论对复合薄膜的三阶非线性效应进行分析, 研究Te颗粒大小对Te/TeO₂-SiO₂复合薄膜的非线性光学性质的影响及其产生机理. 结果表明薄膜制备过电位增大, Te的粒径减小, 颗粒数量多, 颗粒分布趋于均匀, 使得金属颗粒的表面等离子体共振峰红移, 吸收强度增强, 导致三阶非线性光学效应增强, χ⁽³⁾由1064 nm的5.12×10^-7 esu增大为532 nm的8.11×10^-7 esu. 关键词： 碲 二氧化碲 复合薄膜 三阶非线性     

钴离子注入对二氧化钛晶体的结构和光学性能的影响

采用离子注入法制备了钴离子掺杂的金红石相TiO₂样品;离子注入能量、注量分别为40 keV(1×10¹⁶cm^-2),80 keV(5×10¹⁵,1×10¹⁶,5×10¹⁶,1×10¹⁷cm^-2),120 keV(1×10¹⁶cm^-2). 通过XRD,XPS和UV-Vis等手段对掺杂前后样品的结构和光学性能进行了表征,分析了掺杂元素在金红石TiO₂中的存在形式. XRD测试表明随着注入能量的增加晶体的损伤程度增加. UV-Vis测试表明掺杂后所有样品在可见光区的吸收增强; 并且随着注量的增加,注量为5×10¹⁵cm^-2到5×10¹⁶cm^-2范围内注入样品的光学带隙逐渐变小. 关键词： 钴 二氧化钛 离子注入 掺杂