首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
非共线相位匹配LBO飞秒光参量放大器的理论分析   总被引:1,自引:1,他引:0  
对非共线相位匹配LBO飞秒光参量放大器的参量特性进行了分析,结果表明利用这种参量放大器不仅可以实现高的参量增益,还可以获得极宽的参量带宽.因此它特别适合以纳秒级高功率激光作为抽运光,利用OPCPA技术放大飞秒脉冲.  相似文献   

2.
泵浦光波形和脉宽对飞秒激光对比度的影响   总被引:2,自引:2,他引:2       下载免费PDF全文
 采用宽带数值模型,应用四阶龙格-库塔数值算法对三波耦合方程进行数值分析,研究了泵浦光的波形和脉宽在提高光参量啁啾脉冲放大系统输出飞秒激光对比度的作用。结果表明:在泵浦光脉宽较小的条件下,采用平滑的泵浦光波形更有利于提高飞秒激光对比度;在泵浦光脉宽较宽时,飞秒激光对比度得到很好地提高,而对泵浦光波形不敏感;但继续提高泵浦光脉宽并不能进一步改善飞秒激光对比度,而系统的转换效率却显著降低。  相似文献   

3.
飞秒激光双脉冲在研究光泵浦的超快瞬态过程领域具有重要的应用价值,如何实现高准确度的飞秒激光双脉冲的实时测量显得尤为重要.本文提出了一种基于自相关法的飞秒激光双脉冲参量的测量方法,可实现对共光路传输、具有飞秒至皮秒级时间间隔的飞秒激光双脉冲的脉冲间隔、脉冲宽度和强度比的实时测量.实验中采用自相关仪测得了双折射晶体(钒酸钇)分束出的飞秒激光双脉冲的自相关曲线,并用非线性拟合算法求得了飞秒激光双脉冲的脉冲间隔、脉冲宽度和强度比参量.实验结果表明,本文方法与互相关测量方法相比,克服了参考脉冲参量的不确定性对检测准确度的影响,使测量平均准确度提高了48%以上.  相似文献   

4.
研究了飞秒激光诱导单个空气等离子体通道的吸收和辐射特性,给出了等离子体通道吸收系数的解析表达式,并理论推导出了辐射能流率的表达式。与TOPS不透明度数据库查表方法比较,两种方法计算结果符合得很好。分析了吸收和辐射参量对入射激光参量的依赖关系。计算了中心波长800nm,脉宽40fs的飞秒激光空气等离子体通道的吸收和辐射参量的典型数值。结果表明,成单丝情况下等离子体通道的Rosseland吸收系数为0.0270cm-1,辐射能流率为7.87×1010W/m2;窄脉宽长波长的入射激光有利于生成吸收小辐射强的等离子体通道。  相似文献   

5.
利用结合双温模型的分子动力学模拟方法,研究了飞秒激光与金属相互作用的烧蚀机制.采用中心波长为800 nm,能量密度从0.043 J·cm~(-2)到0.40 J·cm~(-2)不等,脉宽分别为70 fs和200 fs的激光烧蚀金属镍和铝材料.靶材的温度、原子位型以及内部压力随时间的演化展示了材料热物性参量特性和激光参量对烧蚀结果的影响.结果显示材料电子热传导率对飞秒脉宽激光下的影响仍然较大;对比铝和镍的结果可知,铝的电子晶格耦合系数比镍的小,故电子晶格间的温度梯度持续时间较长;铝的电子热传导系数比镍的大,所以材料上下表面电子温度耦合的时间缩短.铝薄膜表面在能量密度为0.40 J·cm~(-2)激光烧蚀下呈现纳米尺寸的晶体结构.  相似文献   

6.
刘洪雨  陈立  刘灵  明莹  刘奎  张俊香  郜江瑞 《物理学报》2013,62(16):164206-164206
利用锁模飞秒脉冲激光二次谐波为抽运源, 同步抽运单共振光学参量振荡器, 抽运光中心波长为425 nm, 重复率为76 MHz, 脉宽180 fs, 光学振荡器下转换晶体采用Ⅰ类共线PPKTP, 实验上实现了压缩度为2.58 dB的正交位相压缩光.考虑到实验系统的效率, 可以推知光学参量振荡器输出的下转换光压缩度为 4.48 dB. 关键词: 同步抽运光学参量振荡器 压缩光 锁模飞秒脉冲  相似文献   

7.
利用Ti:sapphire飞秒激光脉冲在微结构光纤包层的次芯中通过参量四波混频效应获得480—550nm的反斯托克斯波,转换效率可高达28%. 通过改变输入光的偏振方向可以调节反斯托克斯波的中心波长. 理论模拟了飞秒激光在次芯中的模式特性和色散特性,较好地解释了实验结果. 关键词: 微结构光纤 飞秒激光脉冲 参量四波混频过程  相似文献   

8.
刘华刚  章若冰  朱晨  柴路  王清月 《物理学报》2008,57(5):2981-2986
采用傅里叶变换的方法将脉冲光分解成不同的频率成分,建立了非单色光抽运的光参量放大耦合方程组的数值求解模型.研究了非单色抽运光对光参量啁啾脉冲放大的小信号增益、大信号增益以及增益带宽的影响.非单色抽运光降低参量放大的增益水平,但同时可提高增益带宽,且抽运光谱宽越宽,对增益带宽的提高作用越大.还进一步从相位失配和参量带宽的角度分析了非单色抽运光使参量放大的增益降低、带宽增大的原因. 关键词: 光参量啁啾脉冲放大 非单色光 增益带宽 飞秒激光  相似文献   

9.
实验研究了飞秒激光脉冲诱导熔融石英的非线性吸收特性,利用激光诱导自由电子等离子体浓度取决于多光子吸收系数和入射光强的关系;数值模拟了激光诱导折射率变化区域的大小,结合非线性吸收机理和飞秒激光脉冲与介质的相互作用,解释了飞秒激光脉冲超精细加工不受衍射极限的约束,可实现纳米级加工的机理结果表明,电介质的电离能越大,飞秒脉冲诱导的折射率变化区域就越小,但要求的激光脉冲能量也越大;为飞秒激光脉冲超精细加工的材料和激光参量选择提供了理论依据.  相似文献   

10.
文章从激光等离子体相互作用的非线性薛定谔方程出发,理论研究了飞秒强激光脉冲在等离子体中的自压缩行为.结果表明在一定范围内随着激光脉冲宽度、激光强度的增大以及等离子体密度的减小,飞秒强激光脉冲在等离子体中传播的自压缩现象越明显.另外通过适当设定参量得到了近似稳定传播的基孤子.  相似文献   

11.
系统研究了核磁共振碳谱和化学位移规律及其定量构谱关系(QSSR).本文研究了一组十元素分子路径指数矢量VPM,并发现它与烷烃化学位移和CCS有良好线性相关性.采用多元线性回归进行准确估计与预测,结果优良.  相似文献   

12.
A parameter-free, nonperturbative calculation of the ΔNγ electromagnetic transition amplitudes GM*(q2), GE*(q2), and the resonant multipole ratio REM(q2)≡E1+3/2(q2)/M1+3/2(q2) is performed in terms of the well-known nucleon isovector Sachs form factor GMV. Our methods are fully relativistic with conservation of the electromagnetic current guaranteed. We find that GM*(q2) decreases more rapidly than the nucleon dipole form factor when −q21 GeV2/c2 and that REM(q2) remains small even for very high four-momentum transfer implying that the perturbative QCD prediction REM(q2)→1 is purely asymptotic and is valid only for extremely high |q2|.  相似文献   

13.
吴祖懿 《波谱学杂志》1986,3(2):147-157
本文提出了予测稠苯芳杂环及其烷基链上质子化学位移的计算方法。 将稠苯芳杂环化合物用凯库勒式表示,计算式为为需考虑的苯环内的乙烯基效应。σmi,ci为各苯环的环流效应。σ1,Hc为各芳杂环的屏蔽效应,对杂环上质子它就是该单独芳杂环上相应质子的δ值,对苯环上质子要将它分解为各结构因素的效应,即:σ1,He=(1/2)d-1δx=y(或σz)+σc-c·σm,H. σx-yσz为杂原子或其基团的屏蔽效应,σc=c为存在于芳杂环中的乙烯基的效应,σm,Hc为芳杂环的环流效应,d为对不同质子所考虑的键数。有取代基时需考虑取代基的效应。计算环上烷基质子的公式为:δ=σp,CH3+ασc,CH3+βσt,CH3+σl,G σl,G为稠苯芳杂环基的某级效应。  相似文献   

14.
《Physica A》1995,220(3-4):585-598
An antiferromagnetic equivalent-neighbour Heisenberg interaction Hi between impurity spins is added to the reduced s-d Hamiltonian Hr previously introduced by simplifying the Kondo s-d exchange Hamiltonian HK. Asymptotic mean-field theory is developed for Hr + Hi, in the presence and absence of external magnetic field, and applied to (La1−xCex)Al2 alloys. Specific heat ci(T) and zero-field susceptibility χi(0,T) curves for (La1−xCex)Al2 are depicted. The coupling constants of Hr + Hi and conduction bandwidth are adjusted so that Tc temperatures for x = 0.2, 0.1 are equal to the experimental values. ci(T) exhibits a jump at Tc and is decreasing for T < Tc. χi(0,T) has a first order pole at Tc which corresponds to the maximum of experimental susceptibility and χi(0,0) > 0. These results improve those obtained earlier on the grounds of Hr theory.  相似文献   

15.
We study the nonresonant three-body decays of B+D(*)−sK+π+ and BdDs(*)−K0π+. We find that these decays can provide the information on the time-like form factors of D(*)sK. We also explicitly investigate BdDs(*)−K*+ decays by discriminating the nonresonant contributions with the unknown D(*)s wave functions being fixed by the measured mode of BdDsK+.  相似文献   

16.
The specific retention volumes, , for adsorption of 21 solute probes on the solid surface of cellulose acetate butyrate (CAB) were determined in the temperature range 343.15 to 403.15 K by inverse gas chromatography (IGC). The weight fraction activity coefficients, , and Flory–Huggins interaction parameters, , were evaluated using . Both and values decreased with increase of temperature in all the solutes. Further, the values increased with increase of chain length in n-alkanes, but in the case of alcohols the trend was reversed. values were less than 0.5 in polar solutes and greater than 0.5 in 1-alkanes and alcohols. The Hansen solubility parameters (HSP) were calculated by relating with the cohesive energy of adsorption of the solutes on the surface of CAB. The adsorption model proposed by Snyder and Karger was used to determine the HSP for the CAB. The dispersive, , polar, , and hydrogen bonding components of HSP decreased with increase of temperature and the relative error associated with these parameters increased with increase of temperature. The characterization of the solid surface of CAB in terms of the three solubility parameter components was analyzed and is discussed.  相似文献   

17.
张典承  张颍  李晓康  贾凤东  李若虹  钟志萍 《物理学报》2018,67(18):183102-183102
本文在多通道量子亏损理论框架下,利用相对论多通道理论,计算了铥原子收敛于4f132F7/2o)6s(7/2,1/2)4o和4f132F7/2o)6s(7/2,1/2)3o的三个偶宇称里德伯系列.通过将计算结果与美国国家标准与技术研究院数据进行比较,展示了两种类型的电子关联效应:1)里德伯系列之间的相互作用,导致里德伯系列的能级出现整体偏移;2)一个孤立的干扰态镶嵌在一个里德伯系列中,破坏了该里德伯系列能级的规则性.  相似文献   

18.
We review the construction of the multiparametric quantum group ISOq,r(N) as a projection from SOq,r (N + 2) and show that it is a bicovariant bimodule over SOq,r(N). The universal enveloping algebra Uq,r(iso(N)), characterized as the Hopf algebra of regular functionals on ISOq,r(N), is found as a Hopf subalgebra of Uq,r(so(N + 2)) and is shown to be a bicovariant bimodule over Uq,r(so(N)).

An R-matrix formulation of Uq,r(iso(N)) is given and we prove the pairing Uq,r(iso(N)) — ISOq,r(N)). We analyze the subspaces of Uq,r(iso(N)) that define bicovariant differential calculi on ISOq,r(N).  相似文献   


19.
The effects of an electric field on the interband transitions in InxGa1−xAs/InyAl1−yAs coupled step quantum wells have been investigated both experimentally and theoretically. A InxGa1−xAs/InyAl1−yAs coupled step quantum well sample consisted of the two sets of a 50 Å In0.53Ga0.47As shallow quantum well and a 50 Å In0.65Ga0.35As deep step quantum well bounded by two thick In0.52Al0.48As barriers separated by a 30 Å In0.52Al0.48As embedded potential barrier. The Stark shift of the interband transition energy in the InxGa1−xAs/InyAl1−yAs coupled step quantum well is larger than that of the single quantum well, and the oscillator strength in the InxGa1−xAs/InyAl1−yAs coupled step quantum well is larger than that in a coupled rectangular quantum well. These results indicate that InxGa1−xAs/InyAl1−yAs coupled step quantum wells hold promise for potential applications in optoelectron devices, such as tunable lasers.  相似文献   

20.
研究了Er1.0P5O14铒非晶玻璃的红外量子剪裁现象. 从吸收谱和激发光谱的计算比较中肯定了Er1.0P5O14非晶 玻璃的1537.0 nm红外荧光为多光子量子剪裁荧光. 从Er1.0P5O14非晶玻璃的可见和红外荧光发射光谱中发现激发2H11/2, 4G11/24G9/2能级所导致的4I13/24I15/2量子剪裁红外荧光很强;基于自发辐射速率、无辐射弛豫速率和能量传递速率等参数的计算,对其量子剪裁机理进行了分析.发现起源于基态的强下转换能量传递{2H11/24I9/2,4I15/24I13/2},{4G11/24I13/2, 4I15/22H11/2},{4G9/24F7/2,4I15/24I13/2}和{4G9/24I13/2, 4I15/22H11/2}是导致Er1.0P5O14非晶玻璃具有强的三光子和四光子量子剪裁红外荧光的原因.研究结果对改善太阳能电池效率有一定意义.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号