2D SnP3: 具有高载流子迁移率和光吸收率的范德瓦尔斯晶体

本文基于第一性原理计算,预测了二维SnP₃层作为新型半导体材料,具有0.71 eV(单层)和1.03 eV(双层)的间接带隙,这与体结构的金属特性不同. 值得注意的是,2D SnP₃具有9.171×10⁴ cm²?V^-1?s^-1的高空穴迁移率和对于整个可见光谱的高光吸收(∽10⁶ cm^-1),这预示2D SnP₃层有望成为纳米电子学和光电子学的候选材料. 有趣的是,本文发现2D SnP₃双层具有与硅类似的电子和光学特性. 考虑到硅基微电子和光伏技术的巨大成功,本文的研究结果将有助于纳米领域的相关研究.     

半花菁LB膜的三阶非线性特性

本文利用Z扫描测量技术首次对半花菁LB膜的三阶非线性光学特性进行了研究.实验结果表明,LB多层膜中的半花菁分子具有较高的三阶非线性折射率n²=2.0×10^-8(esu),这主要是半花菁分子中π电子体系的贡献,并且由于532nm在其Q吸收带内,引起三阶非线性的共振增强效应,实验数据与理论拟合结果符合得很好.半花菁LB膜的三阶非线性的响应时间在30ns以内.     

用近简并三波混频研究半导体掺杂玻璃的非谐振三阶非线性

用近简并三波混频实验方法对半导体CdS_0.4Se_0.6掺杂玻璃在非谐振透明区的三阶光学非线性进行了研究.该实验消除了由于双光子吸收光生载流子的非线性折射产生的五阶非线性效应,仅获得速度快的三阶光学非线性响应.研究结果表明,在非谐振透明区,CdS_0.4Se_0.6掺杂玻璃的三阶非线性极化率并不比它的基底玻璃大很多.量子尺寸效应没有有意义地提高掺杂玻璃中CdS_0.4Se_0.6微晶的三阶非线性极化率,即使较小激子吸收峰的出现也没有发现明显的变化.     

磁场中耦合量子线的三阶非线性光学吸收率

本文研究了磁场中耦合量子线的三阶非线性光学吸收率,并且利用密度矩阵算符理论导出了三阶非线性光学吸收率的解析表达式.最后,以GaAs/Al_xGa_1-xAs耦合量子线为例作了数值计算,并绘出了三阶非线性光学吸收率与磁场B,光子能量h-ω以及间隔D之间的依赖关系.     

氧氩比对SnO2/Ag/SnO2透明导电膜光电性能的影响

在室温及不同的氧氩比条件下,采用射频磁控溅射Ag层和直流磁控溅射SnO₂层,在载玻片衬底上制备出了SnO₂/Ag/SnO₂多层薄膜.用霍尔效应测试仪、四探针电阻测试仪和紫外-可见-近红外光谱仪等表征了薄膜的电学性质和光学性质.实验结果表明:当氧氩比为1:14时,所制得的薄膜的光电性质优良指数最大,为1.69×10^-2 Ω^-1;此时,薄膜的电阻率为9.8×10^-5 Ω·cm,方电阻为9.68 Ω/sq,在400~800 nm可见光区的平均光学透射率达85%;并且,在氧氩比为1:14时,利用射频磁控溅射Ag层和直流磁控溅射SnO₂层在PET柔性衬底上制备出了光电性质优良的柔性透明导电膜,其在可见光区的平均光学透过率达85%以上,电阻率为1.22×10^-4 Ωcm,方电阻为12.05 Ω/sq.     

聚芳香杂环甲烯的三阶非线性光学效应与时间分辨光克尔效应

合成了一系列聚芳香杂环甲烯,包括聚吡咯甲烯和聚噻吩甲烯.采用四波混频法研究材料的共振三阶非线性光学效应(λ＝532nm),其共振二阶超分子极化率γ三阶非线性光学系数分别达到10^-30esu和10^-8esu.选择具有良好溶解性、成膜性的聚吡咯对二甲氨基苯甲烯(PPDMAB),采用飞秒时间分辨光克尔效应方法研究材料的非共振三阶非线性光学效应(λ=790nm).实验表明,翠绿亚胺碱溶液的光克尔信号仅表现一超快响应的成分,归功于π电子云扭转产生的非共振激发.PPDMAB的非共振二阶超分子极化率γ三阶非线性光学系数分别达到γ=5.78×10^-32esu和χ⁽³⁾=1.26×10^-10esu.     

CdxHg1－xTe/SiO2固溶体微晶掺杂玻璃三阶非线性光学性质的

本文首次报道了对采用溶胶凝胶和原位生长工艺制备的Cd_xHg_1-xTe/SiO₂固溶体微品掺杂玻璃进行的三阶非线性光学性质实验研究及其结果。利用回返式简并四波混频技术,测得该固溶体掺杂玻璃的三阶非线性极化率的值为10^-12esu量级。此结果比纯SiO₂基体提高了2个数量级。表明该固溶体掺杂玻璃三阶非线性明显增强,在同样条件下,测得CS₂的三阶非线性极化率x⁽³⁾为(1.7±0.2)×10^-12esu,与国际上报道完全一致。     

GeS2-Ga2S3-CsCl玻璃的三阶非线性光学性能研究

用传统的熔融急冷法制备了组分为(100-2x) GeS₂-xGa₂S₃-xCsCl (x= 15, 20, 25 mol%)系列硫卤玻璃, 测试了样品玻璃的吸收光谱. 采用Z-扫描方法测试了样品的三阶非线性光学特性. 分析了激光光子能量与玻璃三阶非线性光学特性的关系,并研究了组分变化对玻璃的三阶非线性性能的影响. 研究结果表明,光子能量的少许改变可以使非线性吸收系数在一个较大的范围内变化,随着光子能量的增大, 玻璃的非线性吸收系数β 增大;当光子能量趋近于0.5E_g时, β值趋近于0,玻璃有最佳的品质因子; 玻璃样品中CsCl含量的增加使得玻璃的光学带隙E_g增大,短波截止边蓝移,非线性吸收系数β 减小. 但是由于结构与带隙对光学非线性的影响相反,非线性折射率γ 值变化不大. 该结果表明样品的光学非线性性能由光学带隙和结构两方面因素共同决定,对今后研究全光开关用硫系玻璃具有一定的指导意义和参考价值.     

DF化学激光窗口低损耗增透膜

 表述了DF激光波段采CaF₂和硅窗口减反射膜系的结果。分析了设计多层AR膜的方法并给出用ZnSe/YbF₃材料组合的双层和五层AR膜系。计算了各种膜系的理论性能。研究了膜层淀积工艺技术,对于CaF₂和硅窗口,在DF激光波段实验透过率分别为99.54%和99.8%,镀AR膜CaF₂窗口能承受4.3kW/cm²的连续波DF激光辐射。     

一种新型的两态叠加MSCS光场的广义非线性等阶N次方H压缩

本文利用新近建立的多模压缩态理论,详细研究了一种新型的两态叠加多模薛定谔猫态(即MSCS)光场|ψ⁽²⁾〉_q的广义非线性等阶N次方H压缩效应.结果发现:1态|ψ⁽²⁾〉_q是一种典型的非经典光场;当压缩阶数N与腔模总数q这两者之积为偶数,即qN=2p,并且p为奇数亦即p=2m’+1(m’=0,1,2,3,…,…)时,如果各模的初始相位和∑_j=1^qψ_j态间的初始相位差(θ_pq^(I)-θ_nq^(R))、各多模相干态光场的总的平均光子数∑_j=1^qR_j²等满足一定的量子化条件(或者当∑_j=1^qR_j²在总的平均光子数∑_j=1^qR_j²的一系列压缩区内连续取值时),态|ψ(2)〉q总可呈现出周期性变化的、任意阶的广义非线性等阶N次方H压缩效应.2态|ψ⁽²⁾〉_q的第一及第二两个正交分量,其压缩结果(亦即压缩程度和压缩深度)完全相同,但压缩条件不同;两者的等阶N次方H压缩效应呈现出周期性的互补关系.3与文献16相比,本文所研究的态|ψ⁽²⁾〉_q的等阶N次方H压缩效应是比其等阶N次方Y压缩效应更高阶的广义非线性等阶高阶压缩效应.     

Ultrafast non-resonant third-order optical nonlinearity of GeS2–Ga2S3–CdS chalcogenide glass

Ultrafast third-order nonlinear optical responses of 4(1?x)/5GeS₂-(1?x)/5Ga₂S₃-xCdS (x=0.05, 0.10 and 0.15 in mol%) chalcogenide glasses was investigated by using the femtosecond time-resolved optical Kerr effect technique at a wavelength of 800 nm. The largest third-order nonlinear susceptibility of all samples was estimated to be 1.65×10^?13 esu. An ultrafast nonlinear response time of about 250 fs was observed, which was dominantly assigned to the ultrafast distortion of the electron cloud under femtosecond laser excitation. A nonlinear relationship between the third-order nonlinear susceptibility and the introduced amount of CdS was discussed, suggesting a possible disturbance between different polarizable bonds in the glass system.     

Structure dependence of ultrafast third-order optical nonlinearity for GeS2-In2S3-CsI chalcohalide glasses

Ultrafast third-order nonlinear optical responses of GeS₂-In₂S₃-CsI chalcohalide glasses have been measured by using the femtosecond time-resolved optical Kerr effect (OKE) technique at a wavelength of 820 nm. The third-order nonlinear susceptibility was estimated to be as large as 5.12×10⁻¹³ esu. The full width at half maximum of the Kerr signal was 120 fs and its response was dominantly assigned to the ultrafast distortion of the electron cloud. The relationship between the structural units and the third-order nonlinear optical responses was analysed by Raman spectra. It is suggested that the covalent bonds of S-Ge or S-In constituting the tetrahedral units [GeS_4/2] or [InS_4−xI_x], respectively, play an important role in the ultrafast third-order nonlinear optical responses of these chalcohalide glasses.     

Third-order optical nonlinearities of lead-free (Na1−xKx)0.5Bi0.5TiO3 thin films

(Na_1−xK_x)_0.5Bi_0.5TiO₃ (NKBT) (x = 0.1, 0.2, and 0.3) thin films with good surface morphology and rhombohedral perovskite structure were fabricated on quartz substrates by a sol-gel process. The fundamental optical constants (the band gaps, linear refractive indices and absorption coefficients) of the films were obtained through optical transmittance measurements. The nonlinear optical properties were investigated by Z-scan technique performed at 532 nm with a picosecond laser. A two-photon absorption effect closely related with potassium-doping content was found in thin films, and the nonlinear refractive index n₂ increases evidently with potassium-doping. The real part of the third-order nonlinear susceptibility χ⁽³⁾ is much larger than its imaginary part, indicating that the third-order optical nonlinear response of the NKBT films is dominated by the optical nonlinear refractive behavior. These results show that NKBT thin films have potential applications in nonlinear optics.     

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.     

STUDIES ON THE DYNAMICS OF OPTICAL BISTABILITY SWITCHING IN THE INTERNAL FABRY-PEROT CAVITY WITH A CdSxSe1-x-DOPED GLASS CHANNEL WAVEGUIDE

We report the optical bistability in CdS_xSe_1-x-doped glass channel waveguide with rise and fall times of about 24 and 30ps, respectively, in bistable switching by means of fiber coupling input with a power of about 3mW. The third-order nonlinear susceptibility (x⁽³⁾) of CdS_xSe_1-x-doped glass is estimated experimentally to be 1.8×10^-9 esu. The high speed switching and the value of x⁽¹⁾ show that the optical bistability is caused by an optical nonlinearity which can be attributed to the band-filling effect.     

Study of optical properties in a cubic quantum dot

In this paper, the effect of hydrostatic pressure on both the intersubband optical absorption coefficients and the refractive index changes is studied for typical GaAs/Al _x  Ga_1?x As cubic quantum dot. We use analytical expressions for the linear and third-order nonlinear intersubband absorption coefficients and refractive index changes obtained by the compact-density matrix formalism. The linear, third-order nonlinear, and total intersubband absorption coefficients and refractive index changes are calculated at different pressures as a function of the photon energy with known values of box length (L), the incident optical intensity (I), and Al concentration (x). According to the results obtained from the present work, we have found that the pressure plays an important role in the intersubband optical absorption coefficient and refractive index changes in a cubic quantum dot.     

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     

Third-order nonlinear optical response of Au-core CdS-shell composite nanoparticles embedded in BaTiO<Subscript>3</Subscript> thin films

Au-core CdS-shell composite nanoparticles were synthesized by a direct self-assembly process and integrated into BaTiO₃ thin films. Characterization by transmission electron microscopy showed that the average diameter of these composite nanoparticles was about 8 nm. Using the femtosecond time-resolved optical Kerr effect method, we investigated the third-order nonlinear optical response of the Au@CdS nanoparticles embedded in the BaTiO₃ thin films at a wavelength of 800 nm. An ultrafast nonlinear response and a large effective third-order nonlinear susceptibility of χ⁽³⁾=7.7×10^-11 esu were observed. We attributed the enhancement of the third-order optical nonlinearity to a localized electric field effect originating from the core-shell structure under off-surface-plasmon resonance conditions. Received: 13 May 2002 / Revised version: 23 October 2002 / Published online: 3 April 2003 RID="*" ID="*"Corresponding author. Fax: +86-21/6510-4949, E-mail: sxqian@fudan.ac.cn     

Third-order nonlinear optical properties of excitonic state in a semiconductor quantum dot

By considering usual matrix procedures we examine how the exciton affects the nonlinear optical properties of 3-D semiconductor GaAs quantum dot. We calculate the third-order optical susceptibility of the GaAs (well) Al_xGaAs_1?x (barrier), and consequently the refractive index and the absorption coefficient. By increasing the Al content (x) in barrier material, carrier relaxation time is enhanced and the susceptibility peaks and their positions showed a blue shift, which agrees with the existing experimental work. For an anisotropic QD, the third-order nonlinear absorption coefficient depends strongly on the quantum dot width.     

新型Ru配合物三阶非线性光学性质的Z-扫描研究

通过Z-扫描的实验方法测量了几种新型的Ru配合物在460nm处的三阶非线性折射率n₂和非线性吸收系数β,并由此计算出它们的三阶非线性系数χ⁽³⁾.分析了分子结构对其三阶非线性光学性质的影响. 关键词：