非对称耦合量子阱ZnCdSe/ZnSe的喇曼散射谱与非线性光学特性

采用荧光光谱和喇曼散射谱对非对称Ⅱ一Ⅵ族耦合多量子阱Zn1-xCdxSe／ZaSe的结构进行了表征，并对它的非线性光学特性进行了研究。实验中观察到了比较明显的量子阱荧光峰：在喇曼散射谱中观察到了分别对应于与ZnCdSe窄阱和宽阱的一级限制光学模LO1(Lowe Well)和LOI(Wide Well)，及对应于ZnSe／GaAs界面的声子和等离子体的耦合模。实验发现二次谐波信号的强度随着阱间耦合的增强而增强，说明非对称量子阱(AQW)的耦合效应存在一阈值．与理论结果相一致。     

量子阱材料折射率低偏振相关性研究

分析了阱宽、垒高和应变对量子阱材料TE模和TM模折射率的影响,并剖析了其中的物理机理.研究表明:对于量子限制效应带来的量子阱折射率偏振相关性,阱宽越小或垒高越高,折射率偏振相关性越大.压应变增大时,折射率偏振相关性增大,张应变可以克服量子限制效应带来的折射率偏振影响.对于不同阱宽和垒高的量子阱,均存在合适的张应变量使折射率偏振相关性最小,且阱宽越小或垒高越高所需的张应变量越大.根据以上分析,提出量子阱材料折射率低偏振相关设计方法,并据此设计出C波段(1 530～1 565 nm)内折射率低偏振相关(小于0.03)的量子阱材料In0.49Ga0.51As/In0.77Ga0.23As0.5P0.5.研究结果有助于优化设计光网络中关键器件.     

氮化物耦合量子阱中的二次谐波产生极化率:压电与自发极化效应

理论考察了存在强内建电场的纤锌矿GaN/InxGa1-xN耦合量子阱体系的二次谐波产生(SHG)特性,结果发现共振SHG系数达到了10-7m/V的量级,SHG系数对耦合量子阱的结构与掺杂组份呈现非单调的依赖关系.结果还表明,通过选择小尺寸垒宽与大尺寸阱宽的耦合量子阱,并适当降低掺杂组份,可在氮化物耦合量子阱中获得较强的SHG极化率.     

多量子阱有效折射率偏振相关性研究

分析了多量子阱材料各参数对其TE模和TM模有效折射率的影响。结果表明:阱数增多,多量子阱有效折射率降低,当量子阱数目大于3时,其有效折射率的变化不明显。垒厚增加,有效折射率略有降低。存在合适的张应变量使TE模和TM模有效折射率峰值波长接近的同时,折射率差值整体最小,偏振相关性最小。据此提出多量子阱材料有效折射率低偏振相关设计方法,并设计出C波段内(1530~1565 nm)折射率低偏振相关的InGaAs/InGaAsP多量子阱材料。研究结果有助于设计实用化的有效折射率低偏振相关量子阱材料。     

GaAs和量子阱材料倍频效应的初步研究

采用调 Q YAG 激光器研究了半导体材料 GaAs,GaAs:Cr,InGaAs/GaAs 单量子阱(SQW)的倍频效应及其规律。测量了信号大小与晶体对称轴取向及入射、出射光偏振方向的关系。研究表明:材料表层结构的变化对于反射型倍频效应有很大影响。     

一种特殊的非对称量子阱中的光整流效应

运用量子力学密度矩阵算符理论，推导出在一种特殊非对称量子阱中的光整流系数的解析表达式．最后利用典型的GaAs／A1GaAs非对称量子阱进行数值计算，得到了系统的非线性光整流效应和量子阱的非对称性以及入射光子能量之间的变化规律，并在此特殊量子阱中得到了较大的光整流系数，从而为实验上制作较好的非线性材料提供了一种可行的途径。     

非对称GaAs／Al0.3Ga0.7As双量子阱的光学特性和光学非线性

报道用光调制反射谱和光致发光方法对非对称的GaAs/Al_(0.3)Ga_(0.7)As耦合双量子阱研究的实验结果。在300K和77K下测量了光调制反射谱,对实验结果的线形拟合确认了在双量子阱中分别对应子能级11H、11L、13H、22H等的跃迁,并与理论计算结果作了比较。以氩离子激光器488nm激发测量了双量子阱中基态(n=1)荧光峰强度随激发光密度的变化,研究了其非线性效应。用632.8nm激光在弱激发下测量了3.8～300K范围内相应荧光峰随温度的变化,对实验结果作了分析讨论。     

双偏振双波长混合应变量子阱激光器

本文报道了以混合应变量子阱结构为有源区的激光器。对有源区分别采用体材料、匹配量子阱、压应变量子阱和混合应变量子阱结构的激光器进行了比较。混合应变量子阱激光器能同时工作于两种偏振模式，而且两种偏振模式的激射波长不同。结合实验结果，我们可以看出在混合应变量子阱结构中，从偏偏自发辐射谱峰值长差不能推断两种量子陆的能带填充效应大小。     

半导体量子阱中强耦合磁极化子的性质

首次采用线性组合算符结合改进的LLP幺正变换的方法,研究了电子与体纵光学声子强耦合情况下半导体量子阱中磁极化子的性质。导出了无限深量子阱中强耦合磁极化子的振动频率、基态能量和自陷能与阱宽和回旋共振频率的变化关系。对RbCl量子阱进行数值计算,结果表明：强耦合磁极化子的振动频率、基态能量和自陷能随回旋共振频率的增大而增大。振动频率和自陷能随阱宽的增加而增大;基态能量随阱宽的增加而减小,且在阱宽较窄时,表现出奇特的量子尺寸效应。     

抛物势对GaAs非对称半指数量子阱中极化子基态能量的影响

探究了非对称抛物受限势对GaAs非对称半指数量子阱中弱耦合极化子性质的影响。采用线性组合算符方式和两次幺正变换,导出了GaAs非对称半指数量子阱中弱耦合极化子的基态能量随x轴、y轴方向的非对称抛物受限势的受限强度ω_x、ω_y和非对称半指数受限势的两个正参量U_0、σ的变化情况。对GaAs半导体进行了数值计算,结果表明非对称半指数量子阱中弱耦合极化子的基态能量E_0是参量U_0的增函数,而它是另一个参量σ的减函数。非对称抛物受限势的影响表现为基态能量E_0随x轴和y轴方向的非对称抛物受限势的受限强度ω_x和ω_y的增加而迅速增大,表示出量子阱独特的量子尺寸限制效果。     

Electric field effects in AlGaAs-GaAs symmetric and asymmetriccoupled quantum wells

A theoretical study of energy level shift and field-induced tunneling in symmetric and asymmetric coupled quantum wells is presented. Energy level shift is calculated from the time-dependent Schrodinger equation using the inverse power method. The time evolution of an electron wavepackage is shown by the application of the time-development operator of the time-independent Schrodinger equation. Energy level shift in coupled quantum wells is found to be enhanced in comparison to single quantum wells. The energy level shift in coupled quantum wells is found to be nearly linear with the applied field. Oscillation frequencies for electrons in symmetric and asymmetric coupled quantum wells are evaluated versus the applied field and compared to semiclassical prediction. Tunneling lifetimes in symmetric and asymmetric coupled quantum wells are evaluated versus the applied field     

Zero chirp asymmetric Fabry-Perot electroabsorption modulator using coupled quantum wells

A zero-chirp asymmetric Fabry-Perot reflection InGaAs QW modulator is created by placing coupled quantum wells in the intrinsic region of a reverse-biased p-i-n diode asymmetric Fabry-Perot cavity. Unlike single quantum wells which necessarily produce chirping during the switching cycle, these coupled quantum wells provide large absorption changes with zero refractive index changes over the entire voltage swing; the resultant cavity structure shows reflectivity changes with zero experimental phase change over the same voltage range. The tradeoff in reflectivity change required in order to obtain zero chirp is described. This tradeoff is a result of the different switching mechanisms used in coupled quantum wells versus single quantum wells.     

GaAs／AlGaAs非对称耦合双阱光荧光的温度依赖关系

报道了ＧａＡｓ／ＡｌＧａＡｓ非对称耦合双量子阱ｐｉｎ结构在不同温度下的光荧光谱，观察到宽阱与窄阱重空穴激子峰荧光强度随温度上升而较快下降的不同变化关系，结果表明窄阱电子的热发射是导致窄阱光荧光强度随温度上升而较快下降的主要原因。同时观测到宽阱轻空穴激子峰强度特环的温度依赖关系，并分析了其物理机制。     

非对称量子阱中线性和三阶非线性光吸收系数的研究

主要研究了一个特殊非对称量子阱中的线性和三阶非线性光吸收系数。首先利用量子力学中的密度矩阵算符理论和迭代方法导出了线性和三阶非线性光吸收系数的表达式，然后以典型的非对称量子阱GaAs／AIGaAs材料为例作了数值计算。数值结果表明，入射光强以及系统的非对称性对总的光吸收系数有比较大的影响，从而为实验研究提供理论依据。     

Design and performance optimization of optically-pumped mid-infrared intersubband semiconductor lasers

We show that self-consistent simulations of asymmetric coupled double-quantum wells (ACQW) can be used efficiently to increase significantly the optical performances of optically-pumped mid-infrared intersubband semiconductor lasers by increasing the electron concentration in the quantum well. Our calculations, which account for the screening effect and degenerate statistics, show optical gain in excess of 100/cm for pumping intensity of 39 kW/cm/sup 2/ can be achieved. Owing to hot electron effects, the stimulated gain at 77 K is insensitive to the phonon resonance for pumping intensities larger than 400 kW/cm/sup 2/.     

Refractive index modulation based on excitonic effects inGaInAs-InP coupled asymmetric quantum wells

The effect of excitons in GaInAs-InP coupled asymmetric quantum wells on the refractive index modulation, is analyzed numerically using a model based on the effective mass approximation. It is shown that two coupled quantum wells brought in resonance by an applied electric field will, due to the reduction in the exciton oscillator strengths, have a modulation of the refractive index which is more than one order of magnitude larger than in a similar quantum well structure based on the quantum confined Stark effect, but with no coupling between the quantum wells. Calculations show that combining this strong electrorefractive effect with self-photo-induced modulation in a biased-pin-diode modulator configuration, results in an optical nonlinearity with a figure of merit of 20 cm³/J at a wavelength of 1.55 μm. This value is large compared to optical nonlinearities originating from band edge resonance effects in III-V semiconductor materials     

Observation of infrared intersubband emission in optically pumpedquantum wells

Mid-infrared intersubband emission is investigated in GaAs/AlGaAs asymmetric coupled quantum wells exhibiting an energy separation between the ground and first excited subbands close to the LO-phonon energy. The authors show that an infrared emission occurs between excited subbands under intersubband optical pumping     

非对称耦合双量子阱的荧光光谱研究

讨论了耦合双量子阱的光荧光性质，并着重对不同垒宽样品的荧光性质与激发功率的关系进行了详细讨论，分析了导带子带间弛豫过程的竞争。     

非对称耦合双阱P—I—N结构的光伏谱研究

首次报道了GaAs/Al_(0.35)Ga_(0.65)As/GaAs(50(?)/40(?)/100(?))非对称耦合双阱P-I-N结构的室温光伏谱,清楚地观察到双阱的轻、重空穴激子峰,这些激子峰的能量位置与光荧光和光电流谱得到的数据吻合得很好,而且光伏谱谱形非常类似于光电流谱,呈现清晰的台阶状结构。此外,还观察到轻、重空穴激子跃迁对激发光偏振态的依赖,并讨论了产生光伏谱的机制。