利用简化的能级模型分析泵浦探测技术

采用简化的能级模型来模拟和分析在泵浦探测实验中非线性光学材料的动态特性.这种简化模型可以使运算效率大幅提升且能清楚地表明能级模型中关键参数的影响.同时模拟和分析了激发态吸收和双光子吸收在不同参数条件下对泵浦探测实验的影响,指出了激发态吸收和双光子吸收的区别.     

罗丹明6G的非简并双光子吸收特性研究

利用飞秒激光泵浦-探测技术,在实验上研究了常用荧光染料分子罗丹明6G的非简并双光子激发荧光特性,并测试了其非简并双光子吸收截面。与等效波长下文献报道的罗丹明6G的简并双光子吸收截面作对比,发现其非简并双光子吸收截面总是大于简并双光子吸收截面,从实验上证明了双光子吸收过程中的中间态共振增强效应。基于有效态模型,用量子化学的方法从理论上分析罗丹明6G的双光子吸收截面,将理论拟合与实验测试结果进行对比,发现理论与实验具有很好的一致性。     

CdS0.2Se0.8纳米晶掺杂玻璃的超快非线性吸收特性

利用飞秒脉冲通过Z扫描技术和泵浦-探测技术研究了CdS0.2Se0.8纳米晶掺杂的硼酸盐玻璃滤波片RG665的非线性吸收特性。研究结果表明在800 nm波长 130 fs脉冲激光作用下,RG665滤波片表现较强的非线性吸收特性。通过理论分析拟合实验结果证明RG665滤波片在800 nm下的非线性吸收包含双光子吸收及双光子吸收诱导的激发态吸收两部分,得到双光子吸收系数为0.05 cm/GW,激发态吸收截面为e=310-23 m2,以及导带中低能态电子和导带底电子的寿命分别为13 ps和210 ps。研究结果表明CdS0.2Se0.8纳米晶体掺杂的玻璃是一种很好的非线性光学材料。     

双光子吸收染料HMASPS上转换及非线性吸收性能的研究

从实验上研究了一种染料trans 4 [p (N hydroxyethyl N methylamino)styryl] N methylpyridinium p toluenesulfonate(简称HMASPS)双光子抽运的频率上转换及双光子吸收引起的非线性吸收情况。当抽运功率密度超过一定阈值时 ,染料发出超辐射荧光。测量了从 90 0～ 115 0nm抽运波长范围的荧光激射上转换效率和 72 0～ 110 0nm范围的非线性吸收情况。在 92 0nm处具有最大有效双光子吸收截面 44 3× 10 -4 8cm4 s/ photon ,在 10 6 4nm处为2 77× 10 -4 8cm4 s/photon。最高上转换效率 7%位于 990nm ,而在 10 6 4nm为 4 3%。     

泵浦探测法测量染料分子基态恢复时间的研究

本文对泵浦探测法测量染料分子基态恢复时间进行了分析,对以往的结论作了修正。提出用锁模脉冲串激发获得单个脉冲测量结果的方法。测量了BDN染料在不同溶剂中的基态恢复时间。     

CS2宽带光限幅和非线性吸收特性研究

利用ns脉冲激光,研究了CS2在420-470nm波长范围内的非线性吸收和光限幅特性。实验结果表明,CS2对420-450nm波长的脉冲激光具有大的非线性吸收和优良的光限幅性能,随着波长的增加,其非线性吸收和光限幅性能逐渐减小;CS2良好的宽带光限幅性能源于其大的非线性吸收,其非线性吸收机制为双光子吸收（TPA）以及由TPA诱导的激发态吸收（ESA）。     

双光子染料ps激光泵浦下的超辐射和腔激射

本文首次报道了ps激光脉冲泵浦下的有机染料的上转换腔激射，当用1064nm激光（40ps）激发有机染料PSPS[trans-4-（4′-pyrrolidinyl styryl)-N-methyl pyridinium methyl sulfate]时，可以得到中心波长分别为615nm和620nm的超辐射和腔激射，用再吸收现象解释了腔激射相对超辐射的红移现象，用不同条件下再吸收系数的不同解释了超辐射和腔激射相对双光子荧光的蓝移。该染料的399ps的荧光寿命有利于腔激射的产生。我们得到了远大于泵浦光脉冲宽厚的200ps激光振荡，并对此现象进行了解释。     

高效有机非线性光学材料特性的光谱分析

采用了纳秒Nd∶YAG激光器为激发光源泵浦有机分子材料粉末,OMA 系统探测散射光谱的方法,研究材料的非线性光学特性。采集了双氰基为电子受体基团,二甲氨基为电子给体基团,分别以苯基多烯和吡嗪基团为共轭体系构成生色团有机分子材料的散射光谱。比较了线型和Λ型结构以及不同共轭桥对分子内电荷转移效率的影响。观察到D2π2A 线型结构具有较高的倍频转化效率,二阶非线性极化率大;双共轭桥Λ 型结构具有较高的双光子吸收效率,三阶非线性极化率较高。苯基多烯为共轭桥比二氮环庚烷具有更高的分子内电荷转移效率。     

Single-pulse pump-probe measurement of optical nonlinear propertiesin GaAs/AlGaAs multiple quantum wells

Single-pulse ps-pump and ns-probe nonlinear transmission measurements provide carrier-density-dependent optical nonlinear spectra in GaAs/AlGaAs multiple quantum wells grown by metalorganic chemical vapor deposition. The use of the ps pump eliminates the need to know carrier lifetime to determine carrier density. The saturation behavior of changes in absorption coefficient and refractive index are modeled by a simple saturation equation to obtain saturation carrier density. The saturation spectra for different well thicknesses are obtained. The minimum saturation carrier density appears around 150 Å     

飞秒泵浦-探测脉冲下布居转移的场依赖研究

利用含时波包法研究并首次量化了强飞秒泵浦-探测激光场中泵浦场强、泵浦波长和脉宽对三态梯型K2分子态布居数的影响.泵浦场强、泵浦波长和脉宽影响Rabi振荡,导致电子态布居数的周期性变化.量化场参数对激发态布居数的影响表明变化频率随着泵浦场强和脉宽的增大而变化.结果为实验上实现分子的光控制和进一步研究K2分子的动力学性质提供了重要参考.     

端面耦合钛扩散铌酸锂平面光波导中非简并四波混频的研究

在钛扩散LiNbO_3平面光波导中,用端面耦合方法实现了相向传播光脉冲的非简并四波混频效应。实验发现,倍频光以一定的发散角沿垂直于波导表面的方向传播,而发散的机理可用夫琅和费衍射理论解释。     

Theory of nondegenerate four-wave mixing between pulses in asemiconductor waveguide

We develop a perturbation theory for calculating the effects of saturation on nondegenerate four-wave mixing between short optical pulses in a semiconductor optical amplifier. Saturation due to ultrafast intraband dynamics like carrier heating and spectral hole burning is found to be important for pulses on the order of 10-20 ps or less     

Effect of dimensionality on shot-noise suppression in nondegenerate diffusive conductors

We present a theoretical investigation of shot-noise suppression due to long-range Coulomb interaction in nondegenerate diffusive conductors. Calculations make use of an ensemble Monte-Carlo simulator, self-consistently coupled with a one-dimensional Poisson solver. We analyze the noise in a lightly doped active region surrounded by two contacts acting as thermal reservoirs. The effect of momentum space dimensionality on shot-noise suppression is analyzed. Provided significant space-charge effects take place inside the active region, long-range Coulomb interaction is found to play an essential role in suppressing the shot noise at qUk_BT. In the elastic diffusive regime, dimensionality is found to modify the suppression factor γ, which within numerical uncertainty takes values of about 1/3, 1/2 and 0.7 in the cases of 3, 2 and 1 dimensions, respectively.     

碲镉汞深能级载流子弛豫时间的皮秒泵浦-探测研究

采用皮秒泵浦-探测方法研究了碲镉汞材料中非平衡载流子动力学过程,发现其差分透射强度在经过饱和之后出现一个负的极小值,归结为深能级的再吸收过程.采用速率方程模型,并引入两个深能级弛豫时间常数,很好地拟合了差分透射强度的延时曲线.两个深能级弛豫时间常数的存在意味着同时存在两种不同类型的深能级,揭示了碲镉汞材料中深能级特性的...     

Spatiotemporal evolution of probe beams guided between brightsolitons of nondegenerate frequencies

We analyzed an alternative approach for guiding parallel signal beams nested between noninteracting fundamental bright spatial solitons. The numerical results show that stable signal-wave guiding without a cross-talk is obtainable even at small-intensity fluctuations of the control beams (±10%) and at nonperfect alignment of the signal beams with respect to the channels formed by the solitons. Conditions under which the temporal changes of the signal pulses could be asymptotically reduced are discussed     

利用非均匀抽运探测激光增强阿秒脉冲强度

为了增强高次谐波光谱及阿秒脉冲的强度，采用数值求解薛定谔方程的方法，理论研究了H₂+在抽运探测激光驱动下高次谐波辐射特点。结果表明，在抽运激光驱动下，H₂+首先被激发到多光子共振电离区间，进而增大电离几率; 随后在探测激光驱动下，谐波辐射强度得到增强; 当采用不对称非均匀激光场时，谐波截止频率可以进一步延伸，并且谐波平台区只由单一谐波辐射能量峰贡献; 最后通过叠加傅里叶变换后的谐波可获得脉宽在32as的脉冲。该研究对单个阿秒脉冲的产生是有帮助的。     

DFB半导体激光器的非简并四波混频理论分析

建立λ/4相移的DFB-LD的非简并四波混频模型,由耦合波方程分析了信号光、共轭光的前向、后向光波形式,突破以往忽略各光波的反射成分造成的缺陷.在中度耦合系数等条件下得到泵浦光强分布图和信号光、共轭光的透射增益和反射增益图,结果表明泵浦-信号光失谐频率在4THz范围内能获得-20dB以上的波长转换效率.     

Laser-induced anisotropic absorbtion, reflection, and scattering of light in chalcogenide glassy semiconductors

Anisotropy induced in thin-film and bulk samples of chalcogenide glassy semiconductors by the linearly polarized light of different spectral ranges is studied. Three different ranges of exciting photon energy can be distinguished. 1) Above-band-gap light excitation is studied in film samples, two distinct processes are identified in this range: creation of photoinduced defects and their photostimulated orientation and reorientation; a “defect-based” model of photoinduced anisotropy is further developed. 2) Subband-gap light excitation is studied in bulk samples; creation of anisotropically scattered centers is assumed to be the basis of all photoinduced vector phenomena in that spectral range. 3) Superband-gap light excitation is studied in film and bulk samples because the application of differential reflectance spectroscopy; it was shown that not only defects but also main covalent bonds of the glass can be oriented and reoriented by the linearly polarized light that generates the photoinduced dichroism in this spectral interval. Fiz. Tekh. Poluprovodn. 32, 915–922 (August 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.