非线性光学 非线性光学概论

O437 2006043092激子-声子相互作用对三阶非线性光学性质的影响=Effects of exciton-phononinteraction onthird-order nonlin-ear optical properties[刊,中]/姚鸣(宁夏大学物理电气信息学院.宁夏,银川(750001)) ,朱卡的…∥光学学报.—2006 ,26(4) .—605-610在对激子不作任何近似的条件下,对强耦合激子-声子系统中非线性光学性质在理论上进行了研究,结果表明当信号光场频率与激子频率的失谐量等于光学声子的频率时,系统的非线性光学吸收和克尔系数显著增大,从而证明了激子-声子的强相互作用对介质的非线性光学性质的影响相当大。并且,与…     

强耦合激子-声子系统中的三阶非线性光学系数的理论计算

应用Dyson-Maleev变换,对强耦合激子—声子系统中非线性光学性质进行了理论研究.结果表明,当信号光场频率与激子频率的失谐量等于光学声子的频率时,系统的非线性光学吸收和克尔（Kerr）系数显著增大,从而证明了激子-声子的强相互作用对介质的非线性光学性质的影响相当大,并且当考虑激子偏离玻色子模型时,这种影响将进一步增大.     

声子辅助的电磁感应透明和超慢光效应的研究

在对激子不作任何近似的条件下，对强耦合激子-声子系统中光的线性极化率进行了理论计算，证明了当信号光场频率与激子频率的失谐量等于光学声子的频率时，会出现电磁感应透明现象和超慢光效应.并且与对激子作Dyson-Maleev变换近似和玻色近似的结果进行比较，发现对激子无论是否作近似对产生电磁感应透明现象和超慢光效应都没有实质的影响. 关键词： 量子光学 电磁感应透明 激子 声子     

抛物量子点中弱耦合激子的光学声子平均数

研究了电子-体纵光学声子弱耦合情况下,抛物量子点中激子的性质。在有效质量近似下,采用线性组合算符和幺正变换方法研究了抛物量子点中弱耦合激子的基态能量和光学声子平均数。以GaAs半导体为例进行了数值计算,结果表明:弱耦合情况下,激子的光学声子平均数基态的能量和量子点受限强度的增大而减小,随量子点半径的增大而增大。     

温度和极化子效应对准二维强耦合激子基态的影响

采用Huybrechts线性组合算符和Lee-Low-Pines变换法研究了温度和极化子效应对量子阱中激子与界面光学声子强耦合又与体纵光学声子弱耦合体系基态的影响,推导出激子基态的诱生势和基态能量的移动的表达式. 以AgCl/AgBr量子阱为例进行了数值计算,结果表明,由激子-界面光学声子强耦合所产生的激子基态的诱生势和基态能量的移动随温度的升高而增大,而由激子-体纵光学声子弱耦合所产生的激子基态的诱生势和基态能量的移动随温度的升高而减小. 关键词： 量子阱 强耦合激子 极化子效应 温度依赖性     

强激子-声子系统中电磁感应透明理论计算

应用Dyson-M aleev变换,对强耦合激子—声子系统中在考虑相空间填充因子情况下光的线性极化率进行了计算,在理论上证明了强激子-声子的相互作用对产生电磁感应透明起着重要作用,当信号光场频率与激子频率的失谐量等于光学声子的频率时,会出现电磁感应透明现象,并对考虑与不考虑相空间填充因子的两种情况作了比较,发现相空间填充因子对产生电磁感应透明现象没有实质的影响,只是使超慢光效应略有减弱。     

准二维强耦合激子有效质量的温度依赖性

采用Tokuda改变的线性组合算符法和改进的Lee-Low-Pines变换法,研究了温度对量子阱中电子(空穴)与界面光学(IO)声子强耦合又与体纵光学(LO)声子弱耦合激子的有效质量的影响.结果表明,由电子(空穴)-体纵光学声子弱耦合所产生的激子有效质量(Mex*-LO)随量子阱宽N的增加而增大、随电子与空穴间相对距离P的增加而先增大后缓慢减小再趋于稳定,温度T对Mex*-LO及其随N和P变化的规律产生显著影响.同时,Mex*-LO)随T的变化也强烈的受到量子尺寸效应的影响;由电子(空穴)-界面光学声子强耦合所产生的激子有效质量Mcx*-IO随N的增加而减小,随T的升高而增大、随p的增加而先增大后缓慢减小再趋于稳定,但丁对Mex-IO随N和p变化的规律无明显影响.     

温度和极化子效应对准二维强耦合激子基态的影响

采用Huybrechts线性组合算符和Lee-Low-Pines变换法研究了温度和极化子效应对量子阱中激子与界面光学声子强耦合又与体纵光学声子弱耦合体系基态的影响，推导出激子基态的诱生势和基态能量的移动的表达式. 以AgCl/AgBr量子阱为例进行了数值计算，结果表明，由激子-界面光学声子强耦合所产生的激子基态的诱生势和基态能量的移动随温度的升高而增大，而由激子-体纵光学声子弱耦合所产生的激子基态的诱生势和基态能量的移动随温度的升高而减小.     

极性晶体中慢激子极化势的性质

本文讨论极性晶体中慢激子极化势的性质,把作者过去的工作推广到电子和空穴质量不相等的情形。采用微扰法,在忽略反冲效应中不同波矢的声子之间的相互作用后,计算了二级近似的波函数。由此进一步计算了慢激子的极化电势,发现:激子的极化电势受到纵光学声子的屏蔽,其屏蔽长度与纵光学声子的频率、激子的质量的平方根成反比;极化电势和电子、空穴质量有关,在电子、空穴质量比等于1时最小。 关键词：     

极性晶体膜中强耦合激子的性质

在强耦合极化子模型基础上,采用Lee-Low-Pines(LLP)变分法研究了极性晶体膜中激子与表面光学(SO)声子强耦合、与体纵光学(LO)声子弱耦合体系的性质.讨论了极性晶体膜中激子的诱生势与膜厚度和温度的变化关系.结果表明:激子的诱生势不仅与电子-空穴间距离有关,而且与极性晶体膜厚度有关,同时温度对激子诱生势的影响十分显著.     

Nonlinear optical responses due to exciton-phonon interactions in strongly coupled exciton-phonon systems

The excitonic nonlinear optical responses due to exciton-phonon interactions in strongly coupled exciton-phonon systems are investigated theoretically. It is shown that the influence of exciton-phonon interactions on the nonlinear optical absorptions and Kerr nonlinear coefficients is significant as the signal field frequency detuning from the exciton frequency approaches to the optical phonon frequency. How to manipulate the nonlinear optical responses by using the control fields is also presented.Received: 16 March 2004, Published online: 4 May 2004PACS: 42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption - 42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift - 42.25.Bs Wave propagation, transmission and absorption - 72.80.Le Polymers; organic compounds (including organic semiconductors)     

A study of nonlinear optical properties of a negative donor quantum dot

In this paper, we studied the nonlinear optical properties of a negative donor center (D⁻) in a disk-like quantum dot (QD) with a Gaussian confining potential. Calculations are carried out by using the method of numerical diagonalization of Hamiltonian matrix within the effective-mass approximation. A detailed investigation of the linear, third-order nonlinear, total optical absorptions and refractive index changes has been carried out for the D⁻ QD and the D⁰ QD. The linear, third-order nonlinear, total optical absorptions and refractive indices have been examined for a double-electron QD with and without impurity. Our results show that the optical absorption coefficients and refractive indices in a disk-like QD are much larger than their values for quantum wells and spherical QDs and the nonlinear optical properties of QDs are strongly affected not only with the confinement barrier height, dot radius, the number of electrons but also the electron-impurity interaction.     

Absorption Spectra and Refractive Index Changes of an Exciton in a Core/Shell Quantum Dot

The absorption spectra and the refractive index changes are calculated theoretically for an exciton in a core/shell quantum dot. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The dimensionality effect of exciton quantum dots on the optical absorptions has been studied. It has been found that in the same regime, the optical absorption intensities of excitons are much smaller for the core/shell quantum dots than for the two-dimensional quantum rings. The linear and the nonlinear optical absorption coefficients and refractive index changes have been examined with the change of the confinement potential. The results show that the optical absorptions and the refractive index changes are strongly affected by the repulsive core of core/shell quantum dots. Moreover, the calculated results also reveal that as the inner radius increases, the peak values of the absorption coefficients and the refractive index changes of an exciton will show the optical Aharonov–Bohm oscillation in core/shell quantum dots.     

激子效应对双曲型量子线中非线性光学吸收率的影响

本文研究了双曲型量子线的三阶非线性光学吸收率,着重研究了激子对其影响,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A1GaAs/GaAs双曲型量子线为例作了数值计算。数值结果表明,当线宽增加时,激子效应对三阶非线性光学吸收率的影响越来越弱,特别是,当线宽接近于扩散长度时,激子效应将显着减弱。     

Nonlinear intersubband optical absorption in semiparabolic quantum wells

The linear and third-order nonlinear optical absorptions in semiparabolic quantum wells are studied in detail. Analytic formulas for the linear and third-order nonlinear optical absorption coefficients are obtained using the compact density matrix approach. Based on this model, numerical results are presented for typical GaAs/AlGaAs semiparabolic quantum wells. The results show that the factors of the incident optical intensity and the semiparabolic confinement frequency have great influences on the total optical absorption coefficients.     

Anisotropic optical absorption in quantum well wires induced by high-frequency laser fields

The subband structure and optical properties of a cylindrical quantum well wire under intense non-resonant laser field are investigated by taking into account the correct dressing effect for the confinement potential. The energy levels and wave functions are calculated within the effective mass- approximation using a finite element method. It is found that the absorption coefficient and the saturation intensity are strongly affected by the laser amplitude and frequency as well as by the incident light polarization. As a key result, a large anisotropy in the linear and nonlinear optical absorptions for very intense laser field is predicted. These effects can be useful for the design of polarization sensitive devices.     

强耦合表面激子内部激发态的性质

采用线性组合算符和幺正变换方法,研究极性晶体中强耦合表面激子内部激发态的性质.计算了表面激子的激发态能量、激发能量和平均声子数.     

ZnS/CdSe量子点中线性和三阶非线性光吸收系数研究

在有效质量近似下,利用量子力学的密度矩阵理论,采用无限深势阱模型,从理论上研究了ZnS/CdSe柱型核壳结构量子点中线性和三阶非线性光吸收系数。导出了柱型量子点中线性和三阶非线性光学吸收系数的解析表达式,分析了该系统在不同条件下线性和三阶非线性光吸收系数与入射光频率之间的关系。改变系统的参数,该系统的光吸收系数呈规律性变化。计算结果表明:弛豫时间τ、入射光强I和壳半径R2对系统的吸收系数α有很大的影响,从而为实验上研究核壳结构量子点的非线性光学效应提供了必要的理论依据。     

Optical absorptions of an exciton in a disc-like quantum dot under an electric field

An exciton in a disc-like quantum dot (QD) with the parabolic confinement, under applied electric field, is studied within the framework of the effective-mass approximation. Both the electric field and the confinement effects on the transition energy and the oscillator strength were investigated. Based on the computed energies and wave functions, the linear, the third-order nonlinear and the total optical absorption coefficients were also calculated. We found that the optical absorption coefficients with considering excitonic effects are stronger than those without considering excitonic effects and the absorption peak will move to the right side induced by the electron-hole interaction, which shows an excitonic effect blue-shift of the resonance in QDs. The applied electric field may affect either the size or the position of absorption peaks of excitons. However, the applied electric field may only affect the size of absorption peaks of an electron-hole pair without considering excitonic effects. It is very important to take excitonic effects into account when we study the optical absorption for disc-like QDs. We may observe the excitonic effect induced by the external electric field.