Enabling Efficient Blue-Emissive Circularly Polarized Luminescence by In Situ Crafting of Chiral Quasi-2D Perovskite Nanosheets within Polymer Nanofibers

Chiral perovskite materials have intrigued enormous interests because of their appealing chiroptical properties and tailorable non-centrosymmetric structures. However, it remains challenging to realize high-efficiency blue emissive circularly polarized luminescence (CPL) of intrinsic chiral perovskite nanomaterials at room temperature. Herein, a robust and versatile electrospinning strategy is reported for in situ construction of chiral 2D and quasi-2D perovskite nanosheets (PNSs) protected in polymer hybrid nanofibers. It is found that quasi-2D chiral PNS/polymer possesses inherent chirality and enhanced CPL properties at room temperature compared to 2D counterparts. Notably, CPL emission color of chiral quasi-2D PNS/polymer can be tuned from deep blue to sky blue, and a high luminescence dissymmetry values up to −8.0 × 10⁻³ can be achieved. Different perovskites, polymers, and nanofibrous structures are expanded to explore the universality of polymer protected PNSs. Significantly, compared to spin-coated film, the stabilities of quasi-2D PNS/polymer film are greatly improved due to the effective protection of polymer. The obtained PNS/polymer hybrid nanofiber films can be conveniently implemented for circularly polarized light emitting diode devices. This study may open up a new avenue for the scalable fabrication of chiral perovskite nanomaterials of interest and their applications in the CPL related fields.     

Aggregate States and Energetic Disorder in Highly Ordered Nanostructures of para‐Sexiphenyl Grown by Hot Wall Epitaxy

We report on photoluminescence (PL) and thermally stimulated luminescence (TSL) in highly ordered nanostructures of para‐sexiphenyl (PSP) grown by hot wall epitaxy (HWE). A low‐energy broad band is observed in the PL spectra that can be attributed to the emission from molecular aggregates. While the intrinsic exciton emission in steady‐state PL dominates at low temperatures, the emission from aggregates increases with elevating temperature and its magnitude depends sensitively on film preparation conditions. Time‐resolved PL measurements showed that the aggregate emission decays with a life‐time of ≈ 4 ns, which is approximately an order of magnitude larger than the lifetime of singlet excitons. TSL data suggests the presence of an energetically disordered distribution of localized states for charge carriers in PSP films, which results from an intrinsic disorder in this material. A low‐temperature TSL peak with the maximum at around 30 K evidences for a weak energy disorder in PSP films, and has been interpreted in terms of a hopping model of TSL in disordered organic materials.     

Transient electroluminescence determination of carrier mobility and charge trapping effects in heavily doped phosphorescent organic light-emitting diodes

Transient electroluminescence (EL) was used to measure the delay between the excitation pulse and onset of emission in OLEDs based on phosphorescent bis[3,5-bis(2-pyridyl)-1,2,4-triazolato] platinum(ΙΙ) doped into 4,4′-bis(carbazol-9-yl) triphenylamine (CBP), from which an electron mobility of 3.2 × 10⁻⁶ cm²/V s was approximated. Delayed recombination was observed after the drive pulse had been removed and based on its dependence on frequency and duty cycle, ascribed to trapping and de-trapping processes associated with disorder-induced carrier localization at the interface between the emissive layer and electron blocker. The data suggests that the exciton recombination zone is at, or close to the interface between the emissive layer and electron blocker. Despite the charge trapping effects, a peak power efficiency of 24 lm/W and peak external quantum efficiency of 10.64% were obtained. Mechanisms for the electroluminescence and delayed recombination are proposed.     

塑料光纤光栅及其在WDM系统中的应用前景

在对光纤光栅调谐和塑料光纤的研究基础上,提出了一种新的无源器件－塑料光纤光栅。分析表明,它的调谐量可以达到数百纳米,有望在将来的全波光纤ＷＤＭ中对所信道进行解复用。对这种器件在应用中会面临的问题进行讨论。     

Low energy electron excited nanoscale luminescence spectroscopy of erbium doped AIN

We have investigated the optical activity of Er³⁺ ions in AlN via depth-resolved, (5 nm to 250 nm), low energy electron-excited nanoscale (LEEN) luminescence spectroscopy and compared it with the luminescence of an Er-free AlN film. For the Er-free film, there was no emission in the IR from the AlN at any depth, and at higher energies we measured only a broad, weak feature between 1.7–3.25 eV along with an O defect related feature at 3.8 eV, which is significantly enhanced toward the surface. We found strong emission in the AlN:Er films from the first excited → ground state transition of Er³⁺ at 0.80 eV along with many other excited state transitions, although the features are broad compared to those of GaN:Er. The AlN:Er luminescence saturates near a concentration of 10²¹ cm⁻³, at which point we also observe enhanced O defect related luminescence uniformly distributed throughout the film. This finding suggests a role for O in activating the Er at low Er concentrations, while inhibiting the Er activity at high O concentrations.     

基于FDL和TWC的光突发竞争解决方案及性能分析

在光突发交换(OBS)网络中,突发竞争是影响网络性能的一个重要因素,因此如何有效地解决它,成了OBS网络非常重要的问题.在分析当前文献中的解决方案的优缺点后,提出了一种突发竞争解决方案的系统实现.该实现将光纤延迟线(FDL)时城缓存与波长转换器(TWC)波长变换、空城技术结合在一起,构造了一个基于前向转发缓存和反馈循环缓存的两级交换结构.最后从多方面对该系统实现的竞争解决有效性进行了性能分析和计算机仿真,结果表明:它在适当的业务强度(小于0.6)下,能有效改善突发丢失率和突发延迟;同时能降低系统所需的光器件数目.     

基于体光栅的可调谐线型腔双波长掺镱光纤激光器

论述了均匀加宽增益介质中利用净增益均衡原理同时输出双波长激光的可行性,使得双波长各自的损耗等于增益,抑制模式竞争,便可实现双波长输出。验证了上述原理,搭建的线型腔双波长掺镱光纤(YDF)激光器室温下可以实现单波长输出和双波长输出两种运转状态。单波长或者双波长输出时,转动体光栅角度,利用其分光谱和选波长的特性,均可使得波长分别在1013～1078nm的范围内调谐。双波长同时输出时,其线宽分别约为0.012和0.020nm,最大和最小波长间隔约为65.00和1.04nm。双波长间隔较小时,双波长对彼此的抑制影响较间隔大时更为明显。双波长输出功率均衡稳定,最大输出功率可达40.7mW。输出双波长时,该激光器可用于光子混频和拍频产生太赫兹辐射;输出单波长时,由于其波长可调谐的特性,该激光器可用作光学相干层析(OCT)的调谐光源。     

低电压驱动的MEMS F-P可调光学滤波器研究

基于微机电系统（MEMS）技术,研制了一种新颖的光学腔与静电驱动器分离的Fabry-Pérot（F-P）可调谐滤波器。从光学设计、MEMS结构设计、制造工艺与器件测试等开展了F-P可调谐滤波器的研究,成功制备了工作在以1550 nm波长为中心、调谐范围为40 nm和驱动电压低于30 V的MEMS F-P可调滤波器。测试...     

可调谐全固化折叠腔单频倍频Nd:YVO4激光器

采用三镜折叠腔,使用KTP晶体进行内腔倍频,在激光谐振腔内插入标准具,利用标准具的选模调谐特性和激光晶体自身的标准具作用,设计并研制了LD抽运连续内腔倍频可调谐Nd:YVO4全固化激光器,实现了稳定的单频绿光输出,抽运功率1.5W时最大单频绿光输出40mW,频率可调谐范围约200GHz.     

空间级联可调谐光滤波器方式实现光分插复用器

提出一种采用空间级联可调谐光滤波器方式实现的OADM.该器件不但具有集成度高、体积小、插入损耗低、信道间插入损耗差异小的特点,而且能够在控制电路的作用下灵活选择上下路波长及其数量,为构建灵活、高性能的WDM网络提供了选择.