半导体材料中自旋极化的光学注入与探测

综述了自旋电子学的一些新进展,重点介绍了自旋极化的光学注入、弛豫机制和光学探测等方面的内容,并涉及到与自旋有关的自旋霍尔效应(SHE)和纯自旋流等物理效应.     

基于Faster R-CNN的保偏光纤偏振轴检测方法研究

针对基于端面成像的偏振轴检测方法光照鲁棒性不强、无法同时检测多根保偏光纤偏振轴的问题,提出一种基于Faster R-CNN的检测方法.训练Faster R-CNN神经网络模型,通过参数调优增强了应力区识别的鲁棒性,采用基于Zernike矩算法对应力区边缘点进行亚像素级定位以提高测量精度,分析了测量精度与误差的关系.仿真与实验表明,该方法的测量精度达到±0.1°,在增强光照鲁棒性的同时实现了对多根保偏光纤偏振轴的检测.     

多角度偏振成像仪系统级偏振定标方法研究

系统级偏振定标是多角度偏振成像仪(Directional polarization camera, DPC)研制过程中的关键环节,对于提高大气气溶胶和云相态等定量化探测应用具有重要意义。结合矩阵光学和辐射度学理论,建立了多角度偏振成像仪偏振响应定标模型,对关键影响参量进行定标。采用大口径积分球参考光源和分视场测量方法,消除了光楔平板对DPC三检偏通道视场非一致性的影响,实现了高频和低频相对透过率的高精度测量。采用傅里叶级数的分析方法,建立全视场起偏度的测量模型,消除参考光源偏振方位角绝对位置引入的测量误差,实现光学系统偏振特性的准确测量。采用可调偏振度光源和大口径积分球辐射源,开展了偏振定标精度的比对验证实验和精度分析。测试结果表明,全视场偏振定标精度优于0.5\%,自然光状态下的偏振定标精度优于0.05\%,验证了宽视场偏振遥感器偏振辐射响应定标模型的合理性,说明该系统级偏振定标方法可满足宽视场光学偏振遥感器的高精度偏振观测科学应用要求。     

Chiral Plasmonic Response of 2D Ti3C2Tx Flakes: Realization and Applications

The circularly polarized light sensitive materials response can be reached at plasmon wavelengths through the coupling of intrinsically non-chiral plasmonic nanostructure with chiral organic molecules. As a plasmonic background, the different types of metal nanoparticles of various shapes and sizes are successfully tested and an apparent circular dichroism (CD) signal is measured in both, nanoparticles suspensions and after nanoparticle immobilization in substrate. In this work, the creation of plasmon-active 2D flakes of MXenes (Ti₃C₂T_x) is proposed, with the apparent CD response at plasmon wavelength, through the coupling of intrinsically non-chiral flakes with helically shaped helicene enantiomers. This work provides the first demonstration of chiral and plasmon-active 2D material, which shows the absorption sensitive to light intrinsic circular polarization even in plasmon wavelengths range. The appearance of the induced CD signal is additionally confirmed by several theoretical calculations. After the experimental and theoretical confirmation of the optical chirality at plasmon wavelengths, the flakes are utilized for the polarization sensitive conversion of light to heat, as well as for polarization dependent triggering of plasmon-assisted chemical transformation.     

光阱中的CaCO3晶体微粒的光致旋转

从理论上分析了偏振光束与双折射晶体粒子的相互作用过程，讨论了由于光束自旋角动量向晶体粒子的传递所导致的光致旋转效应的原理，并在纳米光镊装置上利用线偏振He-Ne激光器(633nm，10mW)形成了光镊光阱，利用1／4波片来改变光镊光束的偏振状态，在不同的椭圆偏振状态下实现了直径约为几微米的CaCO晶体微粒的捕获和光致转动。同时利用CCD相机和四像限探测器(QD)测量了粒子光致旋转的转动频率，研究了粒子的旋转频率随激光功率的变化关系。结合实验结果从理论上详细讨论了粒子自身的性质，如厚度、半径和晶体粒子的光轴取向等因素对粒子光致旋转转动速度与激光功率关系的影响。     

Spin Polarization of Chiral Amorphous Fe-Ni Electrocatalysts Enabling Efficient Electrochemical Oxygen Evolution

Chiral-induced spin selectivity is recently demonstrated in a range of spin-dependent optoelectronics and electrochemistry. Herein, a new type of amorphous chiral tartaric acid-FeNi coordination polymer fabricated by electrodeposition methods, achieving both high spin-polarization and high electrocatalytic activity for oxygen evolution, is reported. Circular dichroism shows signature optical activity from the coordination polymer. Conductive atomic force microscopy measurements demonstrate a high spin polarization through the chiral electrocatalyst, which significantly suppresses the formation of hydrogen peroxide byproducts compared to the achiral ones. These chiral Fe-Ni electrocatalysts exhibit a low overpotential of 205 and 280 mV to achieve 10 and 100 mA cm⁻², respectively.     

基于偏振光的散射式浊度仪的设计与实现

针对常用光学浊度测量方法容易受背景光影响引起测量误差的问题,提出了一种基于偏振光的垂直散射式浊度测量方案.利用偏振片的起偏和检偏功能,实现偏振光的产生与检测,有效地降低了背景光带来的测量误差.运用低漂移、低噪声的高性能运放电路实现电路系统的驱动与信号处理,提高浊度的测量精度.实验结果显示,在不同的背景光条件下,该浊度仪能够准确测量0～400 NTU浊度范围内的待测溶液的浊度,且测量精度在5％F.S以内,表明该浊度仪具有较强的抗干扰能力.     

基于暗通道先验原理的偏振图像去雾增强算法研究

在装备试验与测试中,常规光学成像系统极易受气象环境(如雾霾、沙尘等)影响,导致探测距离、成像效果、测量精度等受到大幅限制,从而严重影响目标成像效果及关键参数获取。如何增强雾霾条件下光学探测识别能力及成像质量,成为了当前急需解决的关键问题。本文利用偏振成像优势,结合暗通道先验原理,提出了基于暗通道先验原理的偏振图像去雾增强算法。该算法首先利用采集到的偏振图像提取偏振特征,计算偏振度和偏振角;同时,采用基于区域增长算法自动提取出天空区域,对天空区域进行大气光参数估计,获取大气光偏振度及偏振角相关参数估计;然后,结合暗通道先验原理,获取无穷远处大气光强,进而计算各像素点的大气光强;最后,建立在大气物理退化模型基础上,实现图像去雾增强。实例分析与验证中,通过主观评价与客观评价两种方法,对比本文提出的方法和常见其他方法,实际结果表明,本文算法去雾增强能力较强,能有效提升光学系统的探测识别能力及成像质量,对雾霾条件下武器装备关键参数获取具有重要意义。     

一种集成式红外偏振探测器的盲元检测方法研究

现有集成式红外偏振探测器盲元检测主要依据GB/T 17444-2013中的判别方法获取死像元与过热像元,从而进行盲元替代,但是实际使用过程中,探测器的某些像元对偏振光无法进行正常响应,这些元无法通过国标进行剔除,严重影响成像质量,因此需要在原有的盲元检测方法基础上叠加一种偏振盲元检测方法,从而更加精准的对偏振红外探测器进行盲元评价。针对上述问题,本文提出了一种依据消光比获得偏振盲元的方法,从而可以精确实现对偏振器件偏振盲元与常规过热像元、死像元的多维度同时检测。     

基于主动式圆偏振光照射的探测建模与分析

圆偏振光有良好的“偏振记忆”效应,为了验证在 强散射介质中通过圆偏振光的旋性 差异可以有效抑制散射光的影响,实现复杂背景下的目标探测功能。从经典的米氏散射 理论和菲涅尔反射理论出发,结合偏振蒙特卡罗方法,构建了主动式圆偏振光在散射介质中 探测目标的模型,通过追踪每个光子的偏振态变化,统计分析了圆偏振光经过介质散射和目 标反射后的Stokes矢量信息。仿真结果表明,文中建模方法可以明显区分出散射介质中是否 存在被探测目标;不同的介质环境和不同的探测距离都会对目标的偏振成像造成不同程度的 衰减,而圆偏振差分成像及圆偏振度成像均可实现偏振成像的增强处理。文中建模方法可以 为全偏振探测的理论研究及实际应用提供借鉴。     

偏振探测的机理及应用

偏振探测技术已经成为一种重要的探测手段。本文探讨了偏振探测的机理,如物体的表面特性(粗糙度、色泽和电导率等)对光的偏振特性的影响,介绍了偏振探测技术在地物遥感探测、大气探测、水下探测、医学诊断、天文探测、目标检测、图像处理和军事等领域的应用。     

Status and Trends in Advanced SOI Devices and Materials

提供了一种用于安德鲁反射测量样品制备新方法.该方法采用聚焦粒子束刻蚀和磁控溅射,可以获得可控的、干净的、无应力的纳米接触用于自旋极化探测.所制备的样品中,磁性和非磁性材料样品的反射谱都表现出复杂的峰和谷结构,这些结构可能源于与界面相关的零偏压反常以及与激发态相关的准离子相互作用.对另一个Co40Fe40B20合金样品采用简单的钕针尖压针方法进行了对比性测量,反射谱中没有观察到谷结构,但谱结构出现较明显的热扩展,这种热扩展可能来源于界面处的非弹性输运.所有的反射谱目前还不能由现有的理论给出令人满意的解释.利用点接触反射方法获得可靠的自旋极化信息还有赖于接触界面特征的进一步分析.而一个更切合实际的、更完善的理论成为迫切的需要.     

一种用于制备安德鲁反射样品的新方法

提供了一种用于安德鲁反射测量样品制备新方法.该方法采用聚焦粒子束刻蚀和磁控溅射,可以获得可控的、干净的、无应力的纳米接触用于自旋极化探测.所制备的样品中,磁性和非磁性材料样品的反射谱都表现出复杂的峰和谷结构,这些结构可能源于与界面相关的零偏压反常以及与激发态相关的准离子相互作用.对另一个Co40Fe40B20合金样品采用简单的钕针尖压针方法进行了对比性测量,反射谱中没有观察到谷结构,但谱结构出现较明显的热扩展,这种热扩展可能来源于界面处的非弹性输运.所有的反射谱目前还不能由现有的理论给出令人满意的解释.利用点接触反射方法获得可靠的自旋极化信息还有赖于接触界面特征的进一步分析.而一个更切合实际的、更完善的理论成为迫切的需要.     

基于偏振散射对大气中炭黑颗粒物表征

基于光的偏振散射原理提出了一种对大气中炭黑颗粒物进行表征的测量方法.首先利用偏振光子散射的蒙特卡洛模拟方法寻找表征炭黑颗粒物属性的偏振特征参量,进而通过实验对特征参量进行验证.结果表明,获取的偏振参量对炭黑有较好的表征效果.此外,偏振表征不仅可以兼容现有非偏振散射仪器,提供更多颗粒物属性等信息,还可以减少探测角度,优化探测装置.     

Supramolecular Chiral Structures: Smart Polymer Organization Guided by 2D Polarization Light Patterns

Chiral periodic structures and photonic crystals have attracted a great deal of interest due to their applications in advanced photonics. As a consequence, the design and the fabrication of periodic microstructures in photosensitive materials have been widely investigated. Many achievements in the fabrication of such devices have been made over the last decade, but most of the established methods are still restricted to light intensity distribution with different structural shapes and minor attention has been devoted to exploit the vectorial nature of the light coupled with the response of polarization sensitive materials. Here, supramolecular chiral structuring in an amorphous azo‐polymer is demonstrated, coupling the strong and diversified photoresponse of the material with the holographic recording of 2D polarization patterns. The smart polymer organization guided by the complex light field induces periodic chiral microstructures, with spiral‐ or ribbon‐like shape and identical or opposite helicity, characterized by high stability and complete reconfigurability. The holographic structures are theoretically described by means of the Jones matrix method and experimentally investigated, confirming the simultaneous presence of both linear and circular photoinduced anisotropies. These results prove an alternative approach to design a new class of materials with periodic chiral arrangement.     

惰性气体核的自旋交换光抽运中的物理

核自旋极化的惰性气体原子在诸如核物理、材料科学和磁共振成像等许多领域中都有着广泛的应用,核自旋极化技术涉及领域很广,包括原子、分子和光学物理等等。评述了光抽运和自旋交换碰撞中角动量转移和损失的物理。     

Dirac Cone Spin Polarization of Graphene by Magnetic Insulator Proximity Effect Probed with Outermost Surface Spin Spectroscopy

The effects of the proximity contact with magnetic insulator on the spin‐dependent electronic structure of graphene are explored for the heterostructure of single‐layer graphene (SLG) and yttrium iron garnet Y₃Fe₅O₁₂ (YIG) by means of outermost surface spin spectroscopy using a spin‐polarized metastable He atom beam. In the SLG/YIG heterostructure, the Dirac cone electrons of graphene are found to be negatively spin polarized in parallel to the minority spins of YIG with a large polarization degree, without giving rise to significant changes in the π band structure. Theoretical calculations reveal the electrostatic interfacial interactions providing a strong physical adhesion and the indirect exchange interaction causing the spin polarization of SLG at the interface with YIG. The Hall device of the SLG/YIG heterostructure exhibits a nonlinear Hall resistance attributable to the anomalous Hall effect, implying the extrinsic spin–orbit interactions as another manifestation of the proximity effect.     

同时偏振成像仪检偏方位校正研究

同时偏振成像探测技术是近年发展起来的新型遥感探测技术,该技术采用分振幅方式,在同一个探测器上同时获得被探测目标0、45、90、135四个偏振方向的偏振强度图。这四个检偏方位受到仪器自身偏振效应、偏振器件误差和膜层的影响会发生偏离,为了保证偏振探测精度,对系统的四个检偏方位采用Equator-Poles 定标和曲线拟合的方法进行校正,两种方法测量结果一致性在0.4%以内。线偏振度实测精度与理论分析精度都在2%以内,这验证了检偏方位校正的有效性。     

A Passive Optical Fiber Current Sensor Based on YIG

A research on passive optical fiber current sensor based on magneto-optical crystal and a new design of light path of the sensor head are presented. Both methods of dual-channel optical detection of the polarization state of the output light and signal processing are proposed. Signal processing can obtain the linear output of the current measurement of the wire more conveniently. Theoretical analysis on the magnetooptical fiber current sensor is given, followed by experiments. After that, further analysis is made according to the results, which leads to clarifying the exiting problems and their placements.     

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.