光阑对非均匀偏振光传输特性的影响

从光束的相干-偏振(BCP)矩阵和传输理论出发,推导出了非均匀偏振(NUP)光通过光阑后的偏振度和光强分布的一般表示式。给出了一个光强均匀分布NUP光束的数值计算例。结果表明,通过光阑后光束的偏振度和光强分布发生了显著的变化。横平面上偏振度出现了振荡,光强剖面为非均匀分布。但在远场为均匀偏振。     

用微机控遥测量CO_2激光的光强分布

本文给出了用CMC-80B微机控制扫描反射镜的设计思想,驱动电路框图,步进电机编码及微机软件控制框图。同时给出了用微机控制扫描反射镜快速测量CO_2激光光强的实验结果。     

延迟位相在大功率CO_2多模激光束传输与聚焦中的重要性

采用激光光束的延迟位相分析法,研究了大功率CO_2激光束传输与聚焦时光束横截面的大小和光强分布的变换规律。采用大功率激光束光斑质量诊断仪测量了TLP6000型CO_2激光束在不同位置处横截面的大小和光强分布,理论分析与实际测量结果相吻合。根据延迟位相分析法,设计了在焦点附近获得最小的光强起伏变化的光学变换系统。     

内腔式复合波导起偏CO_2激光器的研究

本文提出用空心介质圆形波导和金属平板波导组成复合波导,对波导 CO_2激光进行内腔式起偏,这类小功率偏振 CO_2激光器偏振度优于98%,功率稳定性大于95%,基模输出7～9瓦。     

激光时空特性对双光束相干合成影响分析

从标量衍射理论出发,分析了相干合成光束远场光强的分布特性,并以两路单元激光为例讨论了激光输出时空特性参数初相位、波前、偏振等特性对相干合成远场光强分布的影响,阐明了相干合成的高功率固体激光器必须采用同一个单频窄线宽种子源分束放大技术的原因,并结合高功率固体激光器实际结构特点与可采取的技术手段,提出光路差、光强比、偏振度...     

激光对CO_2激光器中电子能量分布的影响

Nighan利用已知的电子-分子碰撞截面数据,计算了在CO_2-N_2-He混合气体中的电子能量分布函数,同时研究了电子的跃迁速率,在此基础上研究了电子-分子能量变化过程与激光的关系。他的结论是激光对电子能量分布影响不大。但是,Bletzinger得出了相反的结论,他在CO_2-N_2-He混合气体放电实验中观察到了激光对电子能量分布的烧蚀效应。尔后Avivi用置于等离子体中的电探针的伏安特性曲线,研究了激光对电子能量分布的影响。实验结果表明在2电子伏附近,激光使电子能量分布曲线产生明显的变化。本文采用探针电流的两次导数法测量了CO_2激光器中激光对电子能量分布的影响。 Drungjvesteir给出了电子能量分布与探针电     

利用数字技术进行激光横向光强分布分析的研究

本文介绍了利用数字技术进行激光横向光强分布分析的原理。并给出了具体的方案．实现了对激光横向光强分布图像进行锐化处理、生成光强分布的曲线、三维彩色图像及相关函数，并能进行高斯分布拟合检验．     

矢量多高斯-谢尔模型光束在大气湍流中上行链路中的传输特性

为了有效地提高星地激光通信系统的通信性能,从推广的惠更斯-菲涅耳衍射原理出发,系统研究了矢量多高斯-谢尔模型光束在上行链路中的传输特性。研究结果表明,改变光束的横向相干长度能有效地改变其远场光强分布和大气湍流引起的光束展宽。另外,大气湍流会改变矢量多高斯光束的偏振度,但是在远场其偏振度会趋于一个固定值。该研究结果对星地激光通信等有着潜在的应用价值。     

光电流光谱测量CO_2激光动力学参数

分析了CO_2-N_2-He激光介质中调制CO_2激光的光电压波形,其幅度除正比于CO_2(00~o1)能级粒子数的变化量外,还与CO_2分子跃迁能级的热弛豫速率有关。测量得到的光电压与增益、光强、动态阻抗和温度的关系可用类似于CO分子光电流的解析式来表示。     

测定CO_2激光器偏振特性的简易方法

在激光光谱、调制等研究领域内,常常要采用线偏振的激光器,有时还要求光场偏振方向同外加电场或磁场方向成某种角度(例如乎行或垂直),这就需要测定激光器输出激光的偏振取向及偏振度.在可见光波段,通常采用旋转尼科尔棱镜的方法,而在红外波段,便没有类似的棱镜可采用.本文介绍一种简便方法,使被测的CO_2激光通过一个可绕光轴旋转的布鲁斯特窗,测定布氏窗在不同转角下的激光反射及透射强度,即可确定CO_2激光的偏振面及偏振度.这种方法也适用于其他波段的激光器.     

Radiation-Type Metasurfaces for Advanced Electromagnetic Manipulation

Manipulating the phase, polarization, and energy distribution of electromagnetic (EM) waves has facilitated numerous applications. Nowadays, metasurface provides an innovational scenario to carry out more promising and advanced control of EM waves. However, it is a great challenge to manipulate polarization, phase, and energy distribution simultaneously with a low profile. Herein, a class of single-layer radiation-type metasurfaces to achieve advanced EM manipulation is proposed. Desired EM functions can be achieved based on the geometric phase and resonant phase. Such metasurfaces enable the capability to manipulate arbitrary phases and linear polarization states simultaneously. Moreover, arbitrary energy distributions can be controlled. As examples of potential applications, three advanced EM functional devices are presented: a novel multiple-input multiple-output antenna with efficient crosstalk suppression and information encryption, an energy-controllable router, and a metasurface holographic imaging based on power transmission algorithm, respectively. The proposed strategy may open up an alternative way of controlling EM waves with advanced performance and minimalist complexity. Moreover, it may lead to advances in information encoding and cryptography.     

阵列光束的偏振方向对其相干合成远场光强分布的影响

理论推导了线偏振光纤激光器阵列相干合成远场光强分布的表达式,详细研究了激光器的偏振方向对相干合成远场图样分布、中心主瓣的角宽度以及相干合成远场条纹可见度的影响.阵列光束偏振方向的不一致会使相干合成远场光强的峰值功率下降,中心主瓣的宽度增加,远场光强分布有本底漂移,远场条纹可见度下降.     

A polarization-amplitude-phase modulation scheme for improving the power amplifier energy efficiency

To improve the power amplifier (PA) energy efficiency, a polarization–amplitude–phase modulation (PAPM) scheme in wireless communication is proposed. The proposed scheme introduces the signal’s polarization state (PS), amplitude, and phase as the information-bearing parameters. Thus, the data rate can be further enhanced on the basis of the traditional amplitude–phase modulation. Also, since the transmitted signal’s PS completely manipulated by orthogonally dual-polarized antennas is unaffected by PA, PAPM can let PA work in its nonlinear region to acquire high PA efficiency. To further optimize the PA energy efficiency based on PAPM, a constrained optimization problem regarding the output back-off value and the ratio between the data carried by the PS and the amplitude–phase is formulated, and the distribution of the optimum solutions is presented. The simulation results show that PAPM can improve the PA energy efficiency significantly.     

Acoustoelectron interaction in quantum laser heterostructures

The effect of ultrasonic deformation on the polarization properties of semiconductor quantum-well laser radiation is experimentally and theoretically studied at room temperature. It is shown that the observed rotation of the polarization plane is caused by mixing of the light- and heavy-hole levels in the quantum well. Data on the splitting energy of these levels are obtained. The unique capability of the ultrasonic technique for obtaining data on the value and distribution of technological strains in the heterostructure is shown.     

Optical and electrical characterization of (Ga,Mn)N/InGaN multiquantum well light-emitting diodes

(Ga,Mn)/N/InGaN multiquantum well (MQW) diodes were grown by molecular beam epitaxy (MBE). The current-voltage characteristics of the diodes show the presence of a parasitic junction between the (Ga,Mn)N and the n-GaN in the top contact layer due to the low conductivity of the former layer. Both the (Ga,Mn)N/InGaN diodes and control samples without Mn doping show no or very low (up to 10% at the lowest temperatures) optical (spin) polarization at zero field or 5 T, respectively. The observed polarization is shown to correspond to the intrinsic optical polarization of the InGaN MQW, due to population distribution between spin sublevels at low temperature, as separately studied by resonant optical excitation with a photon energy lower than the bandgap of both the GaN and (Ga,Mn)N. This indicates efficient losses in the studied structures of any spin polarization generated by optical spin orientation or electrical spin injection. The observed vanishing spin injection efficiency of the spin light-emitting diode (LED) is tentatively attributed to spin losses during the energy relaxation process to the ground state of the excitons giving rise to the light emission.     

Renormalization of EM fields in application to large-angle scattering from randomly continuous media and sparse particle distributions

The conventional wave-integral equation in electromagnetic scattering, consisting of a sum of directly received vacuum field plus a scattered field that sums weighted vacuum spherical waves from each scatterer, is replaced by one in which renormalized fields containing part of the multiply scattered energy replace the vacuum fields. A first-order approximation in the renormalized equation is applied to bistatic (large-angle) scattering from weak random fluctuations of the permittivity in a distant volume, and to a sparse monodisperse distribution of isotropic particles to yield scattering cross sections with extended validity for the direct polarization. A similar correction is introduced for the cross polarization in the case of backscatter. Differences with other calculations are noted.     

基于S波片和双延迟器的矢量光场偏振调控方法

基于S波片和双延迟器的偏振特性,提出了一种矢量光场的生成及偏振调控方法,该方法能够将标量高斯光束转换为偏振态分布可调谐的矢量光束。结合Stokes-Mueller矩阵算法,建立了矢量光场偏振调控的数学模型,并仿真计算出标量高斯光束经过S波片和双延迟器（包括双1/4波片和双1/2波片两种情况）后的偏振态空间分布。讨论了双延迟器相对旋转时光场偏振分布的演化规律及机理,实验结果与数值仿真结果相互吻合,表明该方法可以实现对标量相干光场的复杂偏振调控,验证了理论分析的正确性和该方法的可行性。     

激光斜程湍流大气传输平均偏振起伏

运用光子密度分布函数和采用大气折射率起伏Von Karmam湍流谱、研究了相干激光通过斜程大气传输时的平均量子偏振起伏。通过唯象方法导出大气折射起伏对光场相位调制关系,从而建立了斜程大气光子密度分布函数模型。基于斜程湍流大气光子密度分布函数导出了平均＂量子偏振度＂的解析关系。结果指出：湍流大气导致光束偏振度起伏满足零均值高斯分布,大气湍流不影响光子偏振度统计平均值。     

Controlling Polarization Dependent Reactions to Fabricate Multi‐Component Functional Nanostructures

In spite of novel lithographic processes that enable new approaches to fabricating materials, directed assembly of multi‐component hybrid devices remains a challenge. Ferroelectric nanolithography exploits polarization dependent surface interactions to pattern nanoparticles, but the factors that control the particle size and distribution are not sufficiently well understood to produce hybrid nanostructures. Here the effects of photon energy, photon flux, and polarization vector orientation on ferroelectric domain specific photoreactions are quantified, leading to an understanding of the nanoparticle deposition mechanism. Patterned nanoparticle arrays functionalized with optically active porphyrin complexes are configured into optoelectronic devices.     

Compound exponential distributions for undermoded reverberation chambers

Novel theoretical first-order probability density functions are derived for the energy density and magnitude of electromagnetic fields inside mode-tuned or mode-stirred reverberation chambers operated at relatively low frequencies. Deviations of physical characteristics for fields in undermoded chambers from those for ideal reverberation are quantified. These deviations are then used as parameters of the distributions. The distribution parameters can be easily and independently calculated from the measured tuner sweep data functions. The derivation is based on an eigenvalue decomposition of the 3/spl times/3 polarization matrix for the stir-averaged local field, followed by a polarization decomposition of the principal components. The theoretical distributions are compared with measured data, showing improved agreement and a significantly lower mismatch at lower frequencies compared to ideal /spl chi//sub 6//sup (2)/ distributions. The previously observed "flattening" of the cumulative distribution function is confirmed, resulting in a now calculable decrease of the mean value and an increase of the uncertainty for field statistics as frequency is lowered.