级联光栅结合Sagnac环的可调谐光纤激光器

提出并验证了一种单-双波长可调谐掺铒光纤激光器。利用级联光纤布拉格光栅(Cascaded Fiber Bragg gratings,Cascaded FBGs)结合Sagnac环结构所产生的复合滤波效应,实现较高精细度滤波,并通过调节环内偏振控制器(Polarization Controller,PC),引入双折射效应,得到波长可调谐的光纤激光器。基于耦合模理论并使用传输矩阵法对该结构的传输特性进行了分析,在此基础上搭建实验系统,验证了理论分析的正确性。实验结果表明:通过调节PC,激光器输出激光的波长范围约为1 555.644～1 556.112 nm,双波长间隔的可调范围约为0.108～0.452 nm,单-双波长的边模抑制比(SMSR)均高于40 dB;在稳定性测试中,输出单-双波长激光的波长最大漂移量小于0.008 nm。该方法具有结构简单、调谐方便、易于实现且精细度较高的优点,可应用于密集波分复用及全光通信系统等领域。     

Applications of Tamm plasmon-liquid crystal devices

ABSTRACT

The Tamm-plasmon-polariton (TPP) occurs at the interface between a metallic film and the photonic-crystal (PC) substrate. Unlike conventional surface-plasmon-polariton (SPP), TPP can be directly excited by both the transverse electric (TE) and transverse magnetic (TM) electromagnetic waves without using additional coupling optics. The fact that the optical functionality of most plasmonics devices is determined after fabrication limits their applications. Tunable SPP devices by applying liquid crystals (LCs) have been widely demonstrated due to their large birefringence and easy controllability via external stimuli. However, actively tuning TPP is difficult because the localised electric field is between the metallic film and PC substrate, the change of refractive index above the metallic film has only small influences on TPP. This article is intended to briefly review recent progress towards using LCs for actively tuning TPP devices. Not only TPP devices can gain benefits from LCs, we will also discuss the applications of TPP for measuring the anisotropy of the alignment films of LC devices. The sensitivity of the proposed scheme will be discussed.     

A switchable ionic liquid with polarity swing-assisted regeneration properties used for the preconcentration of cadmium in biological samples

In the present study the cadmium (Cd) was determined in serum samples of psoriatic patients. The severity of psoriasis was evaluated according to criteria based on standard clinical diagnosis using Psoriasis Area Severity Index (PASI) score. In present study, an innovative tunable green solvent system based microextraction (TSS-ME) was applied for the enrichment of Cd in acid digested serum samples prior to determination with flame atomic absorption spectrometry. The hydrophobic complex of Cd-ammonium pyrrolidine thiocarbamate was extracted in a tunable solvent system which was prepared from a polybasic amine (N, N, N′, N′-tetramethyl-1, 4-diaminobutane), decanol and water system. The tunable green solvent system (TSS) which has zero ionic strength was converted to homogeneous monophasic polar hydrophilic phase via exposure to CO₂ at different pressure and time duration. Then hydrophobic enriched Cd- ammonium pyrrolidine thiocarbamate was back extracted, using HNO₃ (0.1 to 0.5 mol L⁻¹) then the second round of TSS-ME was applied. The acidic aqueous phase enrich with analyte was separated from tunable solvent. The separated TSS was easily reused for up to 10 time for preconcentration purposes without loss of its enrichment character. The smoker and nonsmoker psoriatic patients at PASI >10, have two to three folds higher Cd levels in serum samples than healthy persons.     

含谐振单元和弹性支承谐振单元的声子晶体低频禁带特性研究

在结构中周期性地添加谐振单元可以构造局域共振声子晶体并产生低频禁带。本文提出了一种具有谐振单元和弹性支承谐振单元的声子晶体结构,通过声子晶体理论和振动理论对该结构的禁带特性和禁带调控特性进行了计算与分析。结果表明,该结构可在0 Hz处形成禁带;禁带内对振动的衰减强度由衰减因子和有限结构周期数共同决定;结构中存在1条可调控禁带和3条不可调禁带;可调控禁带可以通过改变谐振单元和弹性支承谐振单元的结构参数加以调控;不可调禁带包括第一禁带,它们能够较为稳定地对一定频率的弹性波产生衰减作用。该结构所具有的禁带特性在管路、桥梁和汽车减振领域具有潜在应用。     

Highly tunable elastic dielectric metasurface lenses

Dielectric metasurfaces are two‐dimensional structures composed of nano‐scatterers that manipulate the phase and polarization of optical waves with subwavelength spatial resolution, thus enabling ultra‐thin components for free‐space optics. While high performance devices with various functionalities, including some that are difficult to achieve using conventional optical setups have been shown, most demonstrated components have fixed parameters. Here, we demonstrate highly tunable dielectric metasurface devices based on subwavelength thick silicon nano‐posts encapsulated in a thin transparent elastic polymer. As proof of concept, we demonstrate a metasurface microlens operating at 915 nm, with focal distance tuning from 600 μm to 1400 μm (over 952 diopters change in optical power) through radial strain, while maintaining a diffraction limited focus and a focusing efficiency above 50%. The demonstrated tunable metasurface concept is highly versatile for developing ultra‐slim, multi‐functional and tunable optical devices with widespread applications ranging from consumer electronics to medical devices and optical communications.

     

操控非线性损耗实现稳定的高功率单频激光及可调谐激光的输出

通过操控线性和非线性损耗,使激光器满足单频运转的物理条件,获得了稳定高功率单频激光输出.利用非线性损耗取代了现有的标准具锁定技术,实现无调制锁定的宽带连续可调谐激光输出.     

Wave-like deformations for oscillating carbon nanotubes

Carbon nanostructures such as nanotubes and fullerenes, represent future materials because of their remarkable mechanical, electrical and thermal properties. Double-walled carbon nanotubes are widely studied as possible gigahertz oscillators, where the inner tube oscillates within the outer tube. These oscillators are believed to generate frequencies in the gigahertz range and typically of the order of 1–74 GHz. They are also known to generate wave-like formations on the outer surface. In this paper, we study such induced deformations on the surface of the outer tube, as generated by the moving inner tube. Following previous authors we assume that double-walled carbon nanotubes can be modelled as transversely isotropic linearly elastic materials. Using a previously derived approximate force distribution for the resultant van der Waals forces arising from the interatomic interactions, we solve a dynamic linearly elastic problem, and show that the resulting solution exhibits wave-like behaviour.     

一类正则化参数自由的线性约束凸优化问题的预测-校正算法

我们对文章的结构做这样的安排:第二节给出本文需要的预备知识;第三节简述单个目标函数问题(1.1)的己有算法和求解可能遇到的困难,第四节给出解决问题的预测-校正方法;第五节和第六节对问题(1.2)分别陈述己有方法的固有困难和我们提出的解决方案.最后,在第七节中,我们为提出的方法给出统一的算法框架,证明这类算法的收敛性和遍历意义下的收敛速率,同时给出我们的一些结论.     

On the hyperbolic order

We define the hyperbolic order of any locally injective holomorphic function between arbitrary hyperbolic domains of the complex plane and study the relation between the hyperbolic order and the Schwarzian derivative for locally injective holomorphic functions from the unit disk into itself.     

非晶CS/RB纳米薄膜的荧光性质

采用低真空物理气相沉积法制备单组份氰基对称二苯代乙烯(CS)纳米薄膜和罗丹明B(RB)纳米薄膜以及CS/RB叠层纳米薄膜。使用荧光分光光度计、X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征薄膜样品的荧光性质、结构和表面形貌。与粉末晶态样品相比,薄膜样品的荧光发射峰数量变多,发射波长范围拓宽到120 nm。有机小分子的非晶聚集态和纳米叠层结构的的纳米效应导致了样品的荧光性质的变化。