Pöschl-Teller势阱中线性与非线性光学吸收系数的计算

非对称性量子阱中的非线性光学效应因其潜在的实用价值而引起了人们的广泛关注,而量子阱内带间的光学吸收问题对研究远红外光学探测器件具有重要的理论指导意义.考虑带间的电子弛豫,用量子力学中的密度矩阵算符理论导出了Pöschl-Teller 势阱中的线性与三阶非线性光学吸收系数的表达式.通过调节Pöschl-Teller势阱中两个可调参数κ和λ,势阱的形状及其非对称性会随着κ和λ的取值不同而明显不同,从而其线性与非线性光学吸收系数的大小也会随势阱参数κ、λ和入射光强的变化而呈规律性的变化,并且当入射光强增强到一定程度会出现较强的饱和吸收现象.     

Pschl-Teller势阱中线性与非线性光学吸收系数的计算(英文)

非对称性量子阱中的非线性光学效应因其潜在的实用价值而引起了人们的广泛关注 ,而量子阱内带间的光学吸收问题对研究远红外光学探测器件具有重要的理论指导意义 考虑带间的电子弛豫 ,用量子力学中的密度矩阵算符理论导出了P schl Teller势阱中的线性与三阶非线性光学吸收系数的表达式 通过调节P schl Teller势阱中两个可调参数κ和λ ,势阱的形状及其非对称性会随着κ和λ的取值不同而明显不同 ,从而其线性与非线性光学吸收系数的大小也会随势阱参数κ、λ和入射光强的变化而呈规律性的变化 ,并且当入射光强增强到一定程度会出现较强的饱和吸收现象     

加偏置电场的双曲线量子阱中线性与三阶非线性光学吸收系数的计算

利用紧致密度矩阵近似方法,研究了加偏置电场双曲线量子阱中的线性与三阶非线性光学吸收系数. 得到了该系统中的线性与三阶非线性光学吸收系数的解析表达式.分析了势阱的形状、外加电场的大小以及入射光场的强度对吸收系数的影响规律. 文章以典型的AlxGa1－xAs/ GaAs双曲线量子阱为例作了数值计算.结果表明：随着势阱宽度的增加,系统的吸收系数将减小;随着外加电场的增加,系统的非对称性增加,系统的吸收系数将增加;随着外加光场强度的增加,系统的吸收系数将减小,并且当光强增加到一定值时会出现明显的饱和吸收现象,这一结论为进一步的实验研究提供了相应的理论依据.     

Pschl-Teller势阱中线性与非线性光学折射率变化(英文)

利用量子力学中的密度矩阵算符理论导出了Pschl-Teller势阱中的线性与三阶非线性光学折射率的解析表达式。Pschl-Teller势阱中有两个可调参数κ和λ,势阱的形状及其非对称性会随势阱参数的取值不同而明显不同,从而其线性与非线性光学折射率变化的大小也会随势阱参数和入射光强的变化而呈规律性的变化。文章以典型的GaAs/AlGaAs势阱为例作了数值计算,数值计算结果表明,势阱的形状和入射光强对光学折射率有着重要的影响。     

Morse势阱中子带间的光吸收

研究了Morse势阱中子带间的光吸收,并且利用密度矩阵算符理论和迭代方法,推导出了线性和三阶非线性子带间的光吸收系数的解析表达式,然后以GaAs/AlGaAsMorse势阱为例进行数值计算。结果表明,线性吸收系数是正的,为总吸收系数作出积极的作用,而三阶非线性吸收为负,抵消了一部分线性吸收,进而得到总的吸收系数;吸收系数随着入射光强度的增大而减小,即出现吸收饱和现象;当势阱参数a增大时,吸收系数增大,即阱宽较窄时,系统吸收的能量较多。若要获得较大的光学吸收系数,就要输入较小的光场强度,并选择适当的势阱参数a和入射光频率。     

电子-声子相互作用对正切平方量子阱中光吸收系数的影响

从理论上研究了电子-声子相互作用对正切平方量子阱中光吸收系数的影响,首先利用微扰论方法求出考虑极化子效应时正切平方量子阱的波函数和能级,然后利用密度矩阵算符理论和迭代法得到光吸收系数的解析表达式,最后以典型的GaAs/AlGaAs正切平方量子阱为例进行数值计算。结果表明,极化子效应对线性吸收系数、三阶非线性吸收系数和总吸收系数都有显著的影响,在相同光强的情况下极化子效应使光饱和吸收现象更加明显;考虑电声相互作用后,总吸收系数的改变量随着势阱宽度b的减小和势阱深度V0的增加而增大。     

非对称耦合量子阱的吸收非线性增强

基于V 形三能级模型运用密度矩阵方程推导了非对称耦合量子阱三阶光学非线性极化率. 具体分析了三阶吸收非线性效率（三阶光学非线性极化率与线性吸收系数之比）随阱间电子相干振荡频率的变化规律. 理论结果表明：三阶吸收非线性效率对阱间电子相干振荡频率相当敏感，当阱间电子相干振荡频率增大时三阶吸收非线性效率显著增强，而当阱间电子相干振荡频率为零时，这种非线性效率类似于单量子阱情况. 与单量子阱相比，对于已设计好的非对称耦合量子阱结构其突出特征表现在，其非线性吸收与色散特性可经由沿材料生长方向偏压进行控制. 据此，我们预期利用这种非对称耦合量子阱结构能设计成光通信中的光限幅器和可控克尔光开关.     

非对称量子阱中的二阶非线性光学极化率

本文主要研究了一个特殊非对称量子阱中的二阶非线性光学极化率,并且利用量子力学中的密度矩阵算符理论和迭代方法导出了二次谐波极化率的解析表达式.最后,以典型的GaAs/AlGaAs非对称量子阱为例作了数值计算.数值结果表明,较大的二次谐波极化率与系统的非对称性有关,系统的非对称性越大,二次谐波极化率越大.     

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。     

纤锌矿InGaN staggered量子阱中的激子态和光学性质

本文将基于有效质量近似下的变分法,理论研究了纤锌矿InGaN/GaN staggered量子阱中的激子态和光学性质.数值结果显示了InGaN量子阱中的量子尺寸和staggered受限垒对束缚于量子阱中的激子态和光学性质有着明显的影响.当阱宽增加时,量子受限效应减弱,激子结合能降低,带间发光波长增加.另一方面,当量子阱中staggered受限势增加时,量子受限效应增强,激子结合能升高,带间发光波长降低.本文的理论结果证明了可以通过调节staggered垒高和量子尺寸来调控纤锌矿InGaN staggered量子阱中的激子态和光学性质.     

P schl-Teller势阱中线性与非线性光学折射率变化

利用量子力学中的密度矩阵算符理论导出了P schl-Teller势阱中的线性与三阶非线性光学折射率的解析表达式。P schl-Teller势阱中有两个可调参数κ和λ,势阱的形状及其非对称性会随势阱参数的取值不同而明显不同,从而其线性与非线性光学折射率变化的大小也会随势阱参数和入射光强的变化而呈规律性的变化。文章以典型的GaAs/AlGaAs势阱为例作了数值计算,数值计算结果表明,势阱的形状和入射光强对光学折射率有着重要的影响。     

Optical absorption of a quantum well with an adjustable asymmetry

The effects of asymmetry and the electric field on the electronic subbands and the nonlinear intersubband optical absorption of GaAs quantum wells represented by a P?schl-Teller confining potential are studied. The potential itself can be made asymmetric through a correct choice of its parameter set and this adjustable asymmetry is important for optimizing the absorption. In that way optimal cases can be created. We calculate the modified wave functions and electronic subbands variationally. The linear and the nonlinear optical intersubband absorption coefficients are calculated. Numerical results for a typical GaAs quantum well are presented. The nonlinear part of the absorption coefficient is strongly modified by the asymmetry parameters while the electric field affects it at smaller values of the parameters. - 78.67.De Quantum wells     

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.     

Linear and nonlinear intersubband optical absorption coefficients and refractive index changes in a quantum box with finite confining potential

In this work, both the intersubband optical absorption coefficients and the refractive index changes are calculated exactly in a quantum box. Analytical expressions for the linear and nonlinear intersubband absorption coefficients and refractive index changes are obtained by using the compact-density matrix approach. Numerical results are presented for typical GaAs/Al_xGa_1−x As quantum box system. The linear, third-order nonlinear and total absorption and refractive index changes are investigated as a function of the incident optical intensity and structure parameters such as box-edge length and stoichiometric ratio. Our results show that both the incident optical intensity and the structure parameters have a great effect on the total absorption and refractive index changes.     

Linear and nonlinear intersubband optical absorption coefficients and refractive index changes in symmetric double semi-V-shaped quantum wells

In this study, the changes in the refractive index and intersubband optical absorption coefficients in symmetric double semi-V-shaped quantum wells are investigated theoretically. The energy levels and the envelope wave functions of an electron confined in finite potential double semi-V-shaped quantum wells are calculated within the effective-mass approximation framework. The analytical expressions of the refractive index and intersubband optical absorption coefficients are obtained using the compact density matrix approach. The effects of the incident optical intensity and structure parameters, such as the barrier width, confinement potential and the well width, on the optical properties of the double semi-V-shaped quantum wells are investigated. The numerical results show that both the incident optical intensity and structure paremeters have a great effect on the optical characteristics of these structures.     

Electronic structure and nonlinear optical properties of a two-dimensional hexagonal quantum dot

In this work electronic structure, the linear and the third-order nonlinear refractive index changes as well as optical absorption coefficients of a two-dimensional hexagonal quantum dot are investigated. Energy eigenvalues and eigenfunctions of the system are calculated by the matrix diagonalization technique, and optical properties are also obtained using the compact density matrix approach. As our results indicate, both the dot size and the confinement potential have a great influence on the intersubband energy intervals, the transition probability and consequently, the linear and the third-order nonlinear refractive index changes and optical absorption coefficients.     

Intersubband optical absorption coefficients and refractive index changes in modulation-doped asymmetric double quantum well

The linear and the third-order nonlinear optical absorption coefficients and refractive index changes in a modulation-doped asymmetric double quantum well are studied theoretically. The electron energy levels and the envelope wave functions in this structure are calculated by the Schrödinger and Poisson equations self-consistently in the effective mass approximation. The analytical expressions of optical properties are obtained by using the compact density-matrix approach. In this regard, the linear, nonlinear and total intersubband absorption coefficients and refractive index changes are investigated as a function of right-well width (Lw₂) of asymmetric double quantum well. Our results show that the total absorption coefficients and refractive index changes shift toward higher energies as the right-well width decreases. In addition, the total optical absorption coefficients and refractive index changes is strongly dependent on the incident optical intensity.