Left-handed and right-handed rotation double function circular polarizer

In order to gain circularly polarized light of left-handed and right-handed rotation by using a fixed device, a left-handed and right-handed rotation double function circular polarizer is designed with two λ/4 retarders and one polarizer, and its operating principle is analysed by matrix optical means. The result indicates that when the monochromatic light enters this circular polarizer in the positive direction and the negative direction,the emergent light should be circularly polarized light, of left-handed and right-handed rotation respectively. The testing system has been established to verify the above results.     

Aligned Thin Films of Discotic Hexabenzocoronenes: Anisotropy in the Optical and Charge Transport Properties

The anisotropy in the optical absorption and photoconductivity of thin layers of mesomorphic derivatives of hexa‐peri‐hexabenzocoronene (HBC) have been investigated for aligned films prepared via three different methods: deposition on friction‐deposited polytetrafluoroethylene (PTFE), zone‐casting (ZC), and Langmuir–Blodgett (LB) multilayer dipping. The ratio of the optical density for light polarized perpendicular to the alignment direction, OD₊, to that for light polarized parallel, OD₌, varies from close to 1.0 up to 12.5 depending on whether the HBC cores are tilted at close to 45° or 90° with respect to the axis of the self‐assembled columnar stacks. For all aligned films the photoconductivity, determined using the electrode‐less flash‐photolysis time‐resolved microwave conductivity technique (FP‐TRMC), was found to be favored in the direction of columnar alignment by up to a factor of 30 for a PTFE‐aligned film. The effect of varying the temperature of the films over a range encompassing the temperature at which the transition from the crystalline solid to the columnar mesophase occurs in the bulk materials has been investigated. High‐temperature annealing increases the optical and conductivity anisotropy for the LB film significantly, but has little effect for the PTFE and the ZC films. The relative efficacy of the different alignment procedures is discussed.     

Zeeman effects in gaseous He-Ne optical masers

In this paper, experimental and theoretical results of a detailed study of the Zeeman effects in a gaseous He-Ne optical maser under weak and normal excitation conditions are given. Attention is confined to the strongest maser emission line (2s2→2p4). Under weak excitation conditions, the maser emission is a doublet of right and left circularly polarized waves. These may belong to either the same cavity mode or different cavity modes, depending on the strength of the applied magnetic field. When viewed through a linear polarizer, the maser emission is amplitude modulated. Under normal excitation conditions, for suitable magnetic fields, the maser could oscillate in at least three modes. The maser emission would then consist of a pair of right circularly polarized waves of two different cavity resonant frequencies and a pair of left circularly polarized waves of different frequencies. In this case, a beat note at the difference frequency is photo-detected without the need for a linear polarizer. An interesting phase relationship among the various components of the maser multiplet is found. This phase relationship can be explained when the nonlinearity due to saturation is taken into account.     

A Nonreciprocal Circular Polarizer

A nonreciprocal circular polarizer has been developed. This ferrite device converts linear polarization propagating in rectangular waveguide into circular polarization propagating in circular waveguide. The sense, right- or left-hand, of the circular polarization is determined by the direction of a longitudinal magnetic field applied to the ferrite. If one sense of circular polarization, e.g., right-hand, is transmitted, then only left-hand circuIar polarization can be received. Performance data indicate good ellipticity with reasonable loss and VSWR for two models of the circular polarizer, and for two devices--a circulator and a nonreciprocal antenna element--based on the polarizer. The antenna element permits one antenna to be used both to transmit and to receive the reflected circularly polarized signals from a target.     

一种径向偏振光的产生方法

为了产生径向偏振光,采用组合半波片和组合线偏振片在腔外对线偏振光做极化整形的方法,进行了理论分析和实验验证。为检测该径向偏振光产生系统的性能,采用旋转检偏器法对输出光束的偏振分布进行了检测,并用经典斯托克斯参量测量法计算了偏振纯度,最后基于马赫-曾德尔干涉的原理,检测了径向偏振光对称区域的线偏振相位关系。结果表明,当组合线偏振片为4个分块时,获得了偏振纯度为80.5%的径向偏振光,并检测出光斑对称区域的线偏振相位差为π。这一结果对在低成本条件下产生高纯度的径向偏振光是有帮助的。     

1339nm单一谱线Nd:YAP脉冲激光器

介绍了一台a轴偏振的1 339 nm Nd:YAP脉冲激光器.通过分析Nd:YAP晶体的能级跃迁和光谱特性,采用偏振片抑制平行于晶体C轴偏振的激光振荡,并通过设计输出耦合镜的透过率抑制晶体a轴偏振的1 064 nm强线的振荡,成功实现a偏振的1 339 nm单一谱线脉冲激光输出.当输入电能量达到75 J时,激光输出能量为0.31 J,电-光转换效率为0.4%,斜率效率为0.52%,激光输出能量不稳定度≤±5%,激光阈值能量为14.5 J,输出脉冲激光的中心波长在1 339.2 nm.     

π‐Conjugated Oligothiophene‐Based Polycatenar Liquid Crystals: Self‐Organization and Photoconductive,Luminescent, and Redox Properties

A series of liquid‐crystalline (LC) π‐ ‐conjugated oligothiophenes bearing three or two alkoxy chains at their extremities has been designed and synthesized. These polycatenar oligothiophenes form various LC nanostructures including smectic, columnar, and micellar cubic phases. These properties depend on the number and length of the terminal alkoxy chains. The hole mobilities for the oligothiophenes have been measured. The layered smectic and columnar structures are capable of transporting holes, leading to mobilities of up to 0.01 cm² V^?1 s^?1. The columnar LC assemblies have also been explored to produce linearly polarized light‐emission. Fine red polarized fluorescence is observed from a uniaxially aligned film of the oligothiophenes. The redox properties of the oligothiophenes both in solutions and in films have been examined. The oligothiophenes exhibit electrochromism upon applying an oxidative potential. The present design strategy is useful for fabricating a variety of functional electro‐active molecular assemblies.     

一种圆极化透镜天线

提出了一款宽频带高增益的圆极化毫米波天线.该天线由一个半球形的介质透镜圆顶以及一个圆柱形极化器结合而成,将传统的扩展半球介质透镜与介质极化器融合在一起,既能将线极化波转化成圆极化波（反之亦然）,又能有效提高天线的增益.该设计与传统的级联结构（透镜级联极化器）不同,它能够用一个器件同时实现两个器件的功能,并且能大大减小系统的体积,降低插入损耗,减少生产成本.此外,该天线采用3D打印技术来实现,加工精度高并且容易生产,适合于毫米波天线的应用.经过验证,该天线的阻抗带宽能达到38%,轴比带宽为36%,圆极化增益达到22 dBic.     

Polarized Superfluorescent Fiber Sources

We report the theoretical and experimental performance of new, linearly polarized superfluorescent fiber sources (SFS). Internal polarization is produced either by splicing a fiber polarizer at an optimum location along a standard Er-doped SFS or by using a single-polarization Er-doped fiber. Numerical simulations predict that when operated in the backward, forward, or double-pass configuration, these SFSs produce nearly twice the power in the desired linear polarization as a standard, unpolarized SFS. This efficiency figure depends weakly on the polarizer location and extinction ratio, but requires a low polarizer insertion loss ( < 0.5 dB). Laboratory prototypes of a backward and a forward polarized SFS are presented that exhibit a power output in the desired linear polarization about 1.75 times larger than that of an unpolarized SFS, and an extinction ratio in excess of 17.5 dB.     

干拉法制备散射偏光片实验研究

散射偏光片是一种外观半透明略带雾度状态的新型光学功能薄膜材料。当自然光入射,一半光透射,一半光散射。这种散射偏光片在透明投影屏幕上具有应用前景,但还没有实现产业化。本文采用干法拉伸聚乙烯醇掺杂液晶(PVA∶LC)制备散射偏光片。首先,配制聚乙烯醇掺杂液晶水溶液乳胶,在平板玻璃上通过流延晾干成膜;然后采用小型拉伸机,边烘烤加热边拉伸至原长的4倍左右,制备出散射偏光片样品;最后,通过实验测试得出样品的透光率40%,偏振度57%。以样品作屏幕观察投影效果,结果显示投影偏振光与样品透光轴正交背投影效果最好。本文对于实现散射偏光片的产业化研究具有重要参考意义。     

Modulation‐Doped Multiple Quantum Wells of Aligned Single‐Wall Carbon Nanotubes

Heterojunctions, quantum wells, and superlattices with precise doping profiles are behind today's electronic and photonic devices based on III–V compound semiconductors such as GaAs. Currently, there is considerable interest in constructing similar artificial 3D architectures with tailored electrical and optical properties by using van der Waals junctions of low‐dimensional materials. In this study, the authors have fabricated a novel structure consisting of multiple thin (≈20 nm) layers of aligned single‐wall carbon nanotubes with dopants inserted between the layers. This “modulation‐doped” multiple‐quantum‐well structure acts as a terahertz polarizer with an ultra‐broadband working frequency range (from ≈0.2 to ≈200 THz), a high extinction ratio (20 dB from ≈0.2 to 1 THz), and a low insertion loss (<2.5 dB from ≈0.2 to 200 THz). The individual carbon nanotube films—highly aligned, densely packed, and large (2 in. in diameter)—were produced using vacuum filtration and then stacked together in the presence of dopants. This simple, robust, and cost‐effective method is applicable to the fabrication of a variety of devices relying on macroscopically 1D properties of aligned carbon nanotube assemblies.     

Reversible Transformation between CsPbBr3 Perovskite Nanowires and Nanorods with Polarized Optoelectronic Properties

CsPbX₃ (X = Cl, Br, I) perovskite nanowires and nanorods are important 1D and quasi 1D semiconductor nanomaterials. They have shown significant prospect in optic and optoelectronic applications, especially for their adaptability to flexible devices, good carrier transport performance, polarized absorption, and emission properties. Due to the high dependence of the property to the morphology, it is crucial to develop synthesis methods with continuous diameter and length tunability of the 1D/quasi 1D perovskites. In this report, a feasibly room temperature synthesis method was developed for ultrathin CsPbX₃(X = Cl, Br, I) perovskite nanowires. By aging the CsPbBr₃ nanowires (≈2*500 nm) under ambient condition with proper concentration and time, the nanowires are transformed to nanorods with controllable diameter and length. Reversibly, the nanorods can be transformed back to nanowires. Equilibrium mechanism is adopted to understand the morphology evolution, and hopefully could be generally applied to many other nano materials. The polarized optoelectronic properties of the nanowires and nanorods are interpreted by a model based on the two-channel anisotropies measurement. Polarized light detectors constructed by oriented assembled nanowires are fabricated to demonstrate their application potentials.     

Wideband reflecting frequency-selective surface polarizer for X-band applications

This paper proposed the design of a broadband linear-to-circular reflecting polarizer for X-band applications. The polarizer is designed with three-arm dipole-shaped unit cells with a full ground plane to get wideband performance. The incident linear polarized wave is converted to a right-handed circularly polarized wave upon reflection from the polarizer. The footprint of the unit cell is 9 × 9 mm, which is printed on a FR-4 substrate. Fabricated prototype is measured for its performances like polarization conversion ratio (PCR), fractional bandwidth, and aperture efficiency. The PCR is about 97%, and the fractional bandwidth is 64% with the aperture efficiency of more than 80%. Polarizer performance is analyzed in transverse electric and transverse magnetic modes, and they are stable up to 40° of various incident angles. The polarizer exhibits the 3-dB axial ratio bandwidth from 8 to 12 GHz, which is suitable for satellite applications.     

Single-Mode Fiber-Type Polarizer

The simple and novel fabrication technique of the fiber-type polarizer has been demonstrated and the polarization characteristics of the polarizer have been investigated. The polarizer structure consists of the eccentric core and the metal coat on the thin buffer layer whose thickness is controlled by chemical etching. The maximum extinction ratio of 41 dB (polarizer length L = 40.8 mm) was obtained at Lambda = 1.15 µm when the buffer layer thickness was about 0.3 µm. Although the insertion loss increases with decreasing the buffer layer thickness, the insertion loss of 0.66 dB was obtained with the extinction ratio of 22 dB (polarizer length L = 21.4 mm). An aluminum coat was superior to a gold coat for low propagation loss and a high extinction ratio.     

Multitap Photonic Microwave Filters With Arbitrary Positive and Negative Coefficients Using a Polarization Modulator and an Optical Polarizer

A novel multitap photonic microwave filter with arbitrary positive and negative coefficients implemented using an electrooptic polarization modulator (PolM) and an optical polarizer is proposed and experimentally demonstrated. In the proposed filter, the optical polarizer is connected at the output of the PolM with its transmission axis aligned at an angle of 45 to one principal axis of the PolM. By adjusting the polarization direction of the input lightwave to be 45 or 135 to one principal axis of the PolM, an inverted or noninverted intensity-modulated optical microwave signal is obtained at the output of the optical polarizer, which leads to the generation of a negative or positive coefficient. A time delay difference between adjacent taps is generated by using a wavelength-dependent delay line. A five-tap photonic microwave filter with arbitrary positive and negative coefficients is demonstrated. The reconfigurability of the filter is also investigated.     

Broadband Defects Emission and Enhanced Ligand Raman Scattering in 0D Cs3Bi2I9 Colloidal Nanocrystals

Excitonic 0D and 2D lead‐halide perovskites have been recently developed and investigated as new materials for light generation. Here broadband (>1 eV) emission from newly synthesized 0D lead‐free colloidal Cs₃Bi₂I₉ nanocrystals (NCs) is reported. The nature of their emissive states as well as the relative dynamics which are currently hotly debated are investigated. In particular, it is found that the broadband emission is made by the coexistence of emissive excitons and sub‐bandgap emissive trap‐states. Remarkably, evidence of enhanced Raman scattering from the ligands is observed when attached to the NCs surface, an effect that is preliminarily attributed to strong exciton‐ligands electronic coupling in these systems.     

A novel polarizer based on directional coupler and surface plasmon polaritons

A novel polarizer with a silver nanoribbon added into a traditional waveguide directional coupler is designed to realize the polarized output of TE mode. A high extinction ratio can be obtained because of the selectivity of surface plasmon polaritons （SPPs） on polarization. The effects of the polarizer parameters on coupling efficiency and extinction ratio are discussed. Simulation results indicate that the coupling efficiency for TE mode can reach about 95%, but only 3% for TM mode, with the extinction ratio of TE mode about 15 dB when the light wavelength is 1550 nm, The polarizer may have potential applications in photonic integrated circuits and quantum information technology.     

Near-millimeter wave polarizing duplexer/isolator

Polarizing beam splitters made of closely spaced parallel tungsten wires have been configured in such a way as to convert linearly polarized radiation from a source into circularly polarized radiation tunably over a broad frequency range. When combined with a third filter polarizer this combination provided 20 dB of isolation of the source from back reflections while having less than 0.5 dB of insertion losses at 245 GHz.     

傅里叶磁光谱仪中的起偏器和检偏器的自动定位及误差分析

在傅里叶变换型磁光谱仪中，起偏器和检偏器的初始方位通常需要在测量前预先定位。提出了一种不需要专门对起偏器和检偏器定位即可完成磁光谱的测量计算的新方法，该方法可以计算出起偏器和检偏器的初始角度值，从而进行自动校准。推导了检偏器旋转角度偏差导致磁光偏转角测量误差的理论公式，并进行了数值分析，给出了测量误差与旋转步数的关系，数值结果表明检偏器角度偏差引起的误差与步数的平方根成反比关系。还给出了一个钴膜样品的磁光克尔角随外加磁场变化的实测曲线。     

Investigation of GaNxP1−x/GaP LED structure optical properties

GaN_xP_1−x alloy represents a novel compound semiconductor that has attracted considerable interest as a candidate for realization of light emitting diodes (LEDs) in the green-red range of the visible spectra. Simple GaN_xP_1−x/GaP LED structures grown by low-preassure metalorganic vapor phase epitaxy and containing different N contents (0.6–2.3%) were investigated. The hierarchy of N complexes that generate different bound states were determined from photocurrent and electroluminescence spectra for different N concentrations in the GaN_xP_1−x layer. From the experimental measurements, it was confirmed that the electroluminescence emission peaks show discrete emission maxima at ∼608 nm and ∼628 nm with increasing N content due to formation of N clusters.