一维对称光量子阱结构多通道滤波特性研究

利用传输矩阵法研究了一维对称光量子阱结构的多通道滤波特性,发现该结构的多透射峰具有分布对称、近似等间距和高透射率等特点,且峰值位置能利用等效理论近似解析求出.透射峰的数目可通过阱区结构参量确定和进行调整,结构的光子禁带范围可通过材料参量的选择获得极大的展宽.该结构只采用两种材料,结构简单,易于制作,具有较大的材料选择性.     

含负折射率缺陷的光量子阱的透射特性及理论模拟

利用转移矩阵方法对含负折射率缺陷的一维光子晶体量子阱结构的透射特性进行了研究。结果表明,当缺陷为偶数个时,结构透射谱中有两个透射峰;当缺陷为奇数个时,透射谱中只有中心处一个透射峰,且随着缺陷层数的增加,该处峰的品质因子逐渐提高。因电磁波在缺陷处的强烈局域,所以阱中局域态的透射率对缺陷的折射率有很强的依赖作用。通过控制入射光的强度可使缺陷的折射率发生微小的改变,进而使局域态的透射率发生明显改变,这样就可制作高效光开关。     

具有三量子阱结构的一维光子晶体透射谱研究

在适当选择结构参数基础上,通过传输矩阵法计算模拟光子晶体(AB)m(CD)n(BA)m结构模型的透射谱,当光子晶体(CD)n的三个导带分别处于光子晶体(AB)m(AB)m相邻的三个禁带中时,构成光子晶体三量子阱结构,在光量子阱透射谱的归一化频率1.0(ωa/2πc),2.0(ωa/2πc)和3.0(ωa/2πc)三处周围,分布着三套具有规律的局域共振峰,出现明显的量子化效应,且三套透过峰数目都可以通过光子晶体(CD)n的重复周期数n来调节,这一现象可用于设计可调性多通道滤波器。     

可实现奇数通道滤波功能的光量子阱透射谱

针对光子晶体(AB)_m(CD)_n(BA)_m模型,选择适当的结构参数,通过传输矩阵法对其透射谱进行计算模拟发现,在归一化中心频率0.5(ωa/2πc)处,当光子晶体(CD)_n的导带处于光子晶体(AB)_m(BA)_m的禁带中,且两者均以中心频率处为对称中心时,构成镜像对称的光子晶体量子阱结构。在光量子阱透射谱的中心频率处及对称的两侧,分布着具有规律的奇数局域共振峰,出现明显的量子化效应,透射峰数目和位置都可以通过光子晶体(CD)_n的重复周期数n来调节,这一现象可用于设计可调性奇数通道滤波器。     

左手介质对一维光量子阱透射谱的影响

通过传输矩阵法理论研究左手介质对一维光子晶体量子阱(AB)m(CBAABC)n(BA)m透射谱的影响,结果发现:当C层为双正介质时,光量子阱透射谱中出现2n+1条窄透射峰,当C层为左手介质时,呈现简并现象,光量子阱透射峰中仅出现2n-1条窄透射峰;当C层左手介质折射率负值增大时,光量子阱透射谱向禁带中心两侧移动,同时透射峰快速变窄;当C层左手介质光学厚度负值减小时,光量子阱透射谱向禁带中心靠拢,同时透射峰迅速变窄;光量子阱透射变窄对左手介质光学厚度的响应灵敏度高于对折射率负值的响应。左手介质对光量子阱透射谱特性的影响规律,可为光子晶体理论研究及新型量子光学器件设计提供参考。     

一维矩形受限光量子阱光传输特性的研究

结合分离变量法和薄膜光学理论推导了一维矩形受限光量子阱的传输矩阵,并分析了一维矩形受限光量子阱结构的传输特性.计算结果表明:相对于非受限光量子阱结构来说,受限光量子阱的带隙和束缚态向高频方向移动,且束缚态的数目也与阱光子晶体的周期数相同.束缚态的频率随模式量子数的增加而线性增加,随矩形边长参量的增加而呈Lorentz函...     

一维光子晶体的透射率特性

基于传输矩阵法,设计多层一维光子晶体,改变层数和入射角度,应用MATLAB语言进行仿真计算,得到入射角度为0.2rad时,8、16、24层和32层一维光子晶体在[9.77-23.39]THz频范围内存在一个低传输率的传输禁带,只是在两侧的低频和高频部分Fabry-Perot峰变得越来越紧密.改变入射角度为0.1rad、0.2rad和0.3rad时,在低频带范围Fabry-Perot峰变化不大,传输禁带依次增大,高频带部分逐渐压缩.研究结论为一维光子晶体传输器件的设计提供参考.     

双重势垒一维光子晶体量子阱内部局域电场分布

利用传输矩阵法理论,研究了双重势垒一维光子晶体量子阱(AB)k(CD)m(DCD)n(DC)m(BA)k的内部局域电场.结果表明:双重势垒光量子阱内部分布着很强的局域电场,且越靠近阱中心,局域电场越强;双重势垒光量子阱垒层特别是内垒层和外垒层厚度同时增大时,内部局域电场快速增强,而且阱中心增强最明显;双重势垒光量子阱阱层宽度增大时,越靠近阱中心,局域电场越强,但阱宽按偶数倍增大时阱中心的局域电场不变并保持恒定极大值,而阱宽按奇数倍增大到一定数值后,光量子阱内部局域电场则趋于阱宽按偶数倍增大时的局域电场恒定极大值.该研究可为分析光量子势阱的量子化效应机理和分立透射谱的形成内因,以及量子光学产品的实际设计等提供指导.     

不同参数对一维光子晶体透射谱的影响

利用传输矩阵法计算并分析了垂直入射下一维光子晶体的透射谱特性,数值模拟得到两种介质的折射率不变,入射波长减小时中心波长减小,禁带宽度变窄。当入射波长不变时,两种折射率比值变大时禁带宽度变大,实验结果为一维光子晶体器件的设计提供了理论依据。     

一维光子晶体禁带特性的研究

应用传输矩阵法研究了一维光子晶体的禁带特性,数值模拟得到了一维光子晶体TE模、TM模和TE/TM模禁带结构,计算结果表明,介质层的厚度发生变化时,禁带宽度发生变化。研究结果为一维光子晶体器件的设计提供了理论依据。     

On the binding energies of excitons in polar quantum well structures in a weak electric field

The binding energies of excitons in quantum well structures subjected to an applied uniform electric field by taking into account the exciton longitudinal optical phonon interaction is calculated. The binding energies and corresponding Stark shifts for Ⅲ-Ⅴ and Ⅱ-Ⅵ compound semiconductor quantum well structures have been numerically computed. The results for GaAs/A1GaAs and ZnCdSe/ZnSe quantum wells are given and discussed. Theoretical results show that the exciton-phonon coupling reduces both the exciton binding energies and the Stark shifts by screening the Coulomb interaction. This effect is observable experimentally and cannot be neglected.     

低维量子磁性和量子海森伯反铁磁体之有效场论

文章对低维量子磁性的基本问题和相关研究进展作了简单评述,强调了量子非线性Sigma模型在研究量子海森伯反铁磁体的低能物理方面所起的作用以及理论本身存在的疑难问题,并简单介绍了作者最近提出的克服这些疑难问题的一个新建议.     

有机多层量子阱的能量转移

采用多源有机分子气相沉积系统制备了不同类型的有机多量子阱结构，利用电化学循环伏安法和吸收光谱、荧光光谱研究了量子阱的类型、光致发光的特性.电化学循环伏安法和吸收光谱的测量结果表明，PBD/8-羟基喹啉铝(Alq₃)有机量子阱为Ⅰ型量子阱结构，NPB/Alq₃和BCP/Alq₃有机量子阱为Ⅱ型量子阱结构.荧光光谱的研究结果表明，PBD/Alq₃和BCP/Alq₃量子阱结构可以实现PBD，BCP向Alq₃能量完全转移，而NPB/Alq₃量子阱结构，NPB和Alq₃之间只是部分能量转移.文中对影响能量转移的因素进行了讨论. 关键词： 有机量子阱 能量转移     

Optimizing the spectral efficiency of photonic quantum well structures

One can construct photonic single quantum well structures by sandwiching a homogeneous medium slab as a defect between two symmetrical photonic crystals (PCs). It is shown that the number of observed resonant peaks increases with increasing slab thickness. It is found that while the slab is composed of alternatively stacked step-index films, the frequencies of these resonant peaks can be adjusted finely by changing the film thickness properly. In this case, the frequency and frequency interval of confined states can be tuned accurately, and the spectral efficiency can be greatly enhanced without increasing the volume of optical devices. Numerical simulation is based on the finite-difference time-domain (FDTD) method.     

Light propagation characteristics in quantum well structures of photonic crystals

Two-dimensional （2D） closed-cavity single quantum well （SQW） and multiple quantum well （MQW） structures are proposed based on the traditional 2D open-cavity SQW structures of photonic crystals. The numerical calculation results show that the proposed structures can greatly improve the optical characteristics compared with the traditional structures. It is found that the barrier thickness has a great impact on the optical characteristics of the closed-cavity MQW structures： when the barrier thickness is narrower, each resonant peak which appears in the SQW would split, the number of split times is just equal to the number of wells, and each well in the MQW structures is a travelling-wave-well, similar to the well in the open-cavity SQW structures; when the barrier thickness is wider, there is no effect of spectral splitting, and each well in the MQW structures is a standing-wave-well, just like the well in the closed-cavity SQW. The physical origin of different field distributions and the effect of the spectral splitting are provided.     

有机量子阱的光学性质

采用多源有机分子气相沉积系统(OMBD)制备了Alq₃，PBD/Alq₃，PBD/Alq₃/PBD单层、双层以及量子阱结构，利用电化学循环伏安法和吸收光谱、荧光光谱研究了量子阱的类型和样品的光致发光特性.电化学循环伏安法和吸收光谱的测量结果表明，PBD/Alq₃有机量子阱为Ⅰ型量子阱结构.荧光光谱的研究结果表明，单层Alq₃的光致发光峰不随Alq₃厚度变化而变化；但是双层PBD/Alq₃结构光致发光峰随Alq₃厚度的减小而发生蓝移；同样对于PBD/Alq₃/PBD量子阱结构光致发光峰随Alq₃厚度的减小而发生蓝移.对引起光谱蓝移的原因进行了讨论. 关键词： 有机量子阱 光谱蓝移     

均匀横向磁场条件下抛物量子阱结构中的共振隧穿

采用简单的数值计算方法研究了均匀横向磁场条件下通过抛物量子阱结构的共振隧穿。计算了几种GaAs-AlxGa1-xAs-GaAs抛物阱结构的透射系数。结果表明：磁场增加时，共振峰向高能区移动，新的共振峰出现；同时讨论了回旋中心在不同位置时，抛物阱结构的J-V 特性。我们发现回旋中心在抛物阱中心时更有助于解释实验，并且能够得到和实验一致的结果：磁场增加，电流峰值减少且向高偏压移动。     

Meshfree eigenstate calculation of arbitrary quantum well structures

A new, explicit, efficient, and meshfree multi-domain spectral method (MDSM) is presented to calculate the eigenstates of arbitrary semiconductor quantum wells (QW). The method is functional expansion based where the quantized energy states are approximated using efficient basis sets and the boundaries are considered using Tau approach. For bounded domains, Chebyshev polynomials and power series are used as the basis sets, while non-orthogonal predefined exponential basis sets are used for the half bounded domains. Many QW structures were studied and the results are compared with published results for validation. The comparisons exhibit the accuracy and efficiency of the presented method. For QWs that can be analyzed analytically, the relative errors in the calculated quantized energy levels are in the order of ¹⁰−12 with very small number of bases in few ms.     

Oscillatory behavior of magneto-optical interband emissions in asymmetric quantum well structures

We report on the oscillatory behavior of the photoluminescence intensity from asymmetric AlGaAs/InGaAs/GaAs quantum well structures in the presence of a perpendicular magnetic field. Two distinct photoluminescence peaks originating from transitions from the ground (e₁) and the first excited (e₂) electronic states to the heavy hole state (hh₁) are observed. The opposite phase of the oscillations shows clearly the competitive process between the transitions from the ground and first excited states. Electron transfer mechanisms cannot explain the origin of these oscillations. The optical oscillations emerge from changes in the effective electron–hole interaction.     

太赫兹量子阱光电探测器光栅耦合的模拟与优化

光栅耦合是量子阱光电探测器探测正入射电磁辐射的常用耦合方法,本文采用模式展开法研究了一维金属光栅太赫兹量子阱光电探测器中的电磁场分布,并给出了器件有源区中的平均光强.研究结果表明,若一维光栅的周期与太赫兹波在器件材料中的波长相当,并且根据器件结构选取合理的光栅占空比,可使器件中的平均光场最强,光栅的光耦合效率最高,从而提高器件的响应率. 关键词： 太赫兹 量子阱光电探测器 光栅