A new variable stiffness absorber based on magneto-rheological elastomer

A new adaptive variable stiffness absorber was proposed based on a smart material, magnetorheological elastomer (MRE), and its vibration control performance was investigated. Before developing the proposed absorber, the MREs were firstly fabricated by curing a mixture of 704 silicon rubber, carbonyl iron particles and a small amount of silicone oil under an external magnetic field. Then the mechanical properties of the fabricated MREs were measured. On the basis of the measured mechanical characteristics, the MRE absorber was developed and its working characteristics were also tested under various input currents and excited frequencies. Finally, the control responses of a two-degree-of-freedom dynamic system with a MRE absorber were presented under a chirp input and used to evaluate the effectiveness of the MRE absorber.

An encryption scheme based on phase-shifting digital holography and amplitude-phase disturbance

In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform. We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.

Terahertz composite imaging method

In order to improve the imaging quality of terahertz(THz) spectroscopy, Terahertz Composite Imaging Method(TCIM) is proposed. The traditional methods of improving THz spectroscopy image quality are mainly from the aspects of de-noising and image enhancement. TCIM breaks through this limitation. A set of images, reconstructed in a single data collection, can be utilized to construct two kinds of composite images. One algorithm, called Function Superposition Imaging Algorithm(FSIA), is to construct a new gray image utilizing multiple gray images through a certain function. The features of the Region Of Interest(ROI) are more obvious after operating, and it has capability of merging ROIs in multiple images. The other, called Multi-characteristics Pseudo-color Imaging Algorithm(Mc Pc IA), is to construct a pseudo-color image by combining multiple reconstructed gray images in a single data collection. The features of ROI are enhanced by color differences. Two algorithms can not only improve the contrast of ROIs, but also increase the amount of information resulting in analysis convenience. The experimental results show that TCIM is a simple and effective tool for THz spectroscopy image analysis.

Observation and optimization of 2 μm mode‐locked pulses in all‐fiber net anomalous dispersion laser cavity

We integrally demonstrate 2μm mode-locked pulses performances in all-fiber net anomalous dispersion cavity.Stable mode-locking operations with the center wavelength around 1950–1980 nm can be achieved by using the nonlinear polarization rotation structure and properly designing the dispersion management component.Conventional soliton is firstly obtained with a total anomalous dispersion cavity.Due to the contribution of commercial ultra-high numerical aperture fibers,net dispersion is reduced to-0.077 ps2.So that stretched pulse with 19.4 nm optical bandwidth is obtained and the de-chirped pulse-width can reach 312 fs using extra-cavity compression.Under pump power greater than 890 mW,stretched pulse can evolve into noise-like pulse with 41.3 nm bandwidth.The envelope and peak of such broadband pulse can be compressed with up to 2.2 ps and 145 fs,respectively.The single pulse energy of largely chirped stretched and noise-like pulse can reach 1.785 nJ and 1.53 nJ,respectively.Furthermore,extra-cavity compression can also contribute to a significant increase of peak power.

Mode-Field-Diameter and the Coupling Loss between Inner and Outer Segment of Photoreceptors

The characteristics of optical waveguide of human photoreceptors play important roles in vision. The mode-field-diameter (MFD) is a very important parameter of a single-mode waveguide, and it is related to many important optical characteristics of a single-mode waveguide. Here we show that MFDs of outer segments of human foveal cones are close to the minimum values at their geometric diameter for outer segments of foveal cones. Small MFD of outer segment is important for eyes to have high spatial resolution and low interaction between neighboring cones. We propose that the ellipsoids of foveal cones act as spot size converters to reduce the coupling losses between myoids and outer segments.

Design and Fabrication of Two Kinds of Photonic Crystal Fibers

As a new type optical fiber,because of its particular optical properties,photonic crystal fibers(PCFs) have attracted the academic and industrial field widespread attention.So,the researches about PCFs have made great progress in recent decade.In this paper,two kinds of PCFs constructions are numerically investigated and its leakage-loss properties are simulated.Based on the results of calculations,both the two types of PCFs are fabricated using glass capillary tube stacking.And the process of fiber drawing is described in this paper.

Short Pulse Width and High Peak Power 457 nm Deep Blue Laser with V-Type Cavity

An intracavity frequency doubling acousto-optically Q-switched Neodymium-doped Yttrium Orthvanadate (Nd:YVO4) 457 nm blue laser by employing a three-mirror folded cavity was demonstrated. With the incident pump power of 40.4 W, the maximum average output power of 439 mW 457 nm laser, and the minimum pulse duration of 86.14 ns and the maximum peak power of 510 W were achieved at 10 kHz. The M2 factors are 1.23 and 1.61 in X and Y directions, respectively. The power stability in two hours is better than 2%.

Numerical study of three phase shifts and dual corrugation pitch modulated(CPM) DFB semiconductor lasers based on reconstruction equivalent chirp technology

A distributed feedback(DFB) semiconductor laser with three phase shifts based on reconstruction equivalent chirp(REC) technology is proposed and investigated numerically.With the combination of multiple phase shifts and corrugation pitch modulated(CPM) structure,we also propose a novel and more complex structure named dual CPM,which has a flatter light power distribution along the laser cavity compared with the true double phase shifts DFB laser diode(LD),while the P-I curves are nearly the same.The proposed dual CPM structure is also designed and analyzed based on REC technology.The simulation results show that,the DFB semiconductor laser with complex structure such as phase shifts,or even arbitrary variation of the grating period can be achieved equivalently and easily by changing the sampling structure.But its external characteristics are almost the same as those DFB lasers with true phase shifts,or true arbitrary variation of the grating period.The key advantage of the REC technology is that it varies only the sampling structure and keeps the seed grating(actual grating in sampling structure) period constant.So its fabrication needs only low-cost and standard holographic exposure technology.Therefore we believe this method can achieve the high-end and low-cost DFB LD for mass production.

Multichannel fiber optic Fabry-Perot nonscanning correlation demodulator

A multichannel fiber-optic Fabry-Perot （F-P） demodulator based on nonscanning correlation demodula- tion is proposed. The demodulator principle is analyzed, and the prototype of nonscanning correlation demodulation fiber-optic F-P demodulator is made and tested. The measurement range of the prototype is from 10 to 40 μm, the demodulation resolution is 8 nm, and its stability is 7 nm. This method provides a feasible solution, which guarantees the practicability of the fiber-optic F-P sensor network.

Ferroxidase-like activity of Au nanorod/Pt nanodot structures and implications for cellular oxidative stress

铂 nanoparticles (NP ) 被报导模仿各种各样的抗氧化剂酶并且可以因此由减少反应的氧生产积极生物效果种类(ROS ) 层次。在这张手稿，我们报导磅 NP 由在金 nanorods (Au@Pt NDR ) 上扔铂 nanodots ferroxidase 作为酶模仿。Au@Pt NDR 显示出 pH 依赖的象 ferroxidase 一样活动并且在中立 pH 价值举办更高的活动。有人的房间线(肺腺癌 A549 和正常支气管的上皮的房间线 HBE ) 的 Cytotoxicity 结果证明 Au@Pt NDR 经由 endocytosis 和 translocate 被收起进房间进 endosome/lysosome。Au@Pt NDR 在比 0.15 n 低的 NDR 粒子集中有好 biocompatibility。然而，面对 H 2 O 2, lysosomelocated NDR 展出象 peroxidase 一样活动因此增加 cytotoxicity。面对 Fe 2+, ， NDR 的象 ferroxidase 一样活动由消费 H 2 O 2 。当在生物系统采用 Au@Pt NDR 时，彻底的考虑应该被给这行为。

Three alkaline earth metal-organic frameworks based on fluorene-containing carboxylates:syntheses,structures and properties

Three metal-organic frameworks,{[Mg_2(MFDA)_2(DMF)_3]·0.5H_2O}_n(1),{[Ca(MFDA)(DMF)(H_2O)]·0.5DMF}_n(2)and[Ca(MFDA)(DMF)_2]_n(3)(DMF=N,N-dimethylformamide)have been synthesized by the solvothermal reactions between the ligand 9,9-dimethylfluorene-2,7-dicarboxylic acid(H_2MFDA)and the corresponding metal salts,respectively.The single crystal X-ray structural analyses reveal that compounds 1-3 display three-dimensional structures based on the M(Ⅱ)-O-C chains.It is interesting that the MFDA ligands in 1-3 have different dihedral angles between the two carboxylate groups ranging from 9.9(1)°to 41.8(2)°.All of compounds exhibit strong ligand-centered blue emissions under UV lights.Their thermal properties have also been studied.

Monolithically integrated stretchable photonics

Mechanically stretchable photonics provides a new geometric degree of freedom for photonic system design and foresees applications ranging from artificial skins to soft wearable electronics.Here we describe the design and experimental realization of the first single-mode stretchable photonic devices.These devices,made of chalcogenide glass and epoxy polymer materials,are monolithically integrated on elastomer substrates.To impart mechanical stretching capability to devices built using these intrinsically brittle materials,our design strategy involves local substrate stiffening to minimize shape deformation of critical photonic components,and interconnecting optical waveguides assuming a meandering Euler spiral geometry to mitigate radiative optical loss.Devices fabricated following such design can sustain 41%nominal tensile strain and 3000 stretching cycles without measurable degradation in optical performance.In addition,we present a rigorous analytical model to quantitatively predict stressoptical coupling behavior in waveguide devices of arbitrary geometry without using a single fitting parameter.

Current-voltage characteristics of light-emitting diodes under optical and electrical excitation

The factors influencing the current-voltage（I-V） characteristics of light-emitting diodes（LEDs） are investigated to reveal the connection of I-V characteristics under optical excitation and those under electrical excitation.By inspecting the I-V curves under optical and electrical excitation at identical injection current,it has been found that the I-V curves exhibit apparent differences in voltage values.Furthermore,the differences are found to originate from the junction temperatures in diverse excitation ways.Experimental results indicate that if the thermal effect of illuminating spot is depressed to an ignorable extent by using pulsed light,the junction temperature will hardly deflect from that under optical excitation,and then the I-V characteristics under two diverse excitation ways will be the same.

Single-wall carbon nanotube assisted all-optical wavelength conversion at 2.05μm

We fully demonstrate the special requirements of a mid-infrared all-optical wavelength converter.The construction mechanism of a 2.05μm all-optical wavelength converter based on the single-wall carbon nanotube[SWCNT]is proposed.Systematic experiments are carried out,and the converter device is successfully developed.With the assistance of SWCNT-coated microfiber,the conversion efficiency up to-45.57 d B is realized,and the tuning range can reach9.72 nm.The experimental results verify the correctness of the proposed mechanism and the feasibility of the converter device so that it can be a new technical approach for all-optical wavelength conversion beyond 2μm.We believe the research can extend the application of this composite waveguide in the field of all-optical communication.

Optical properties of＇ Au-core Pt-shell nanorods studied using FDTD simulations

Au-core/Pt-shell nanorods （Au@Pt NRs） have been prepared by a Au nanorod-mediated growth method, and they exhibit high electromagnetic field enhancements under coupling conditions. Boosted by a long-range effect of the high electromagnetic field generated by the Au core, the electromagnetic field enhancement can be controlled by changing the morphology of the nanostruc- tures. In this study, we report the results on the simulations of the electromagnetic field enhancement using a finite difference time domain （FDTD） method, taking the real shapes of the Au@Pt NRs into account. Due to the ＂hot spot＂ effect, the electromagnetic field can be localized between the Pt nanodots. The electromagnetic field enhancement is found to be rather independent of the Pt con- tent, whereas the local roughness and small sharp features might significantly modify the near-field. As the electromagnetic field enhancement can be tuned by the distribution of Pt nanodots over the Au-core, Au@Pt NRs can find potential applications in related areas.

Lanthanide-organic frameworks based on terphenyl-tetracarboxylate ligands:syntheses,structures,optical properties and selective sensing of nitro explosives

Three isostructural three-dimensional(3D) lanthanide-based metal-organic frameworks [Ln_2L(H_2L)(NMP)_2].H_2O(Ln=Sm(1), Eu(2), Gd(3); H_4L=1,1′:4′,1″-terphenyl-2′,4,4″,5′-tetracarboxylic acid; NMP=N-methyl-2-pyrrolidone) have been synthesized and structurally characterized. In 1–3, two Ln3+ ions are doubly-bridged by two oxygen atoms of two carboxylate groups to form the dinuclear Ln_2(OCOO–)_2 unit. Each Ln_2(OCOO–)_2 unit links with four H_2L^(2-) ligands and four L4. ligands to lead to the 3D framework,which can be rationalized as a new trinodal 4,4,8-connected(44.62)(45.6)(412.616) topological network by considering the dinuclear Ln_2(OCOO–)_2 units as 8-connected nodes and L^4./H_2L^(2-) ligands as planar 4-connected nodes, respectively. 1 and 3 exhibit blue emission originated from the ligand with the emission maximum at 384 nm, while 2 shows intense characteristic red emission of Eu^(3+) ions and weak ligand-centered emission. Moreover, 2 has fluorescent quenching response towards the aromatic nitro compounds, especially for the 3,4-dinitrotoluene(3,4-DNT) with the linear Stern-Volmer relationship in the concentration range of 0–1 mM and the quenching constant(Ksv) of 2.084×10~3 M^(-1).

Dark spatial solitons sequence in the biased centrosymmetric photorefractive crystal

We theoretically investigate the evolution of dark screening spatial solitons originating from the quadratic electro-optic effect in biased centrosymmetric photorefractive(CP) crystal by using beam propagation method(BPM). The results indicate that the multiple dark solitons sequence can be obtained in the CP crystal with the odd or even initial conditions. If the initial width of the dark notch is smaller, only a fundamental soliton or a Y-junction soliton pair is generated. When the initial width of the dark notch and the bias electric field are increased, the multiple dark spatial solitons sequence is formed, which realized a progressive transition from a low-order soliton to a higher-order solitons sequence in both odd and even conditions. The solitons characteristic is similar to that of screening solitons in the non-centrosymmetric photorefractive(NCP) crystals.

All-optical NRZ wavelength conversion using a Sagnac loop with optimized SOA characteristics

We investigated the all-optical wavelength conversion technique for non-return-to-zero（NRZ） signals based on a Sagnac loop interferometer using an SOA. For the wavelength conversion of the NRZ signal at and above40 Gbit/s, we used an in-house numerical SOA model to analyze the influence of the SOA carrier characteristics and the SOA length on the performance of the Sagnac loop. We found that the SOA carrier recovery time should be between 2 and 3 times of one bit duration in order to get optimum NRZ wavelength conversion. In addition to the carrier recovery time requirement, SOAs with a shorter physical length are preferred to be used in the Sagnac interferometer.

Influence on the propagation velocity of SAW by a force applied on surface

When a force is directly applied to the propagation surface of surface acoustic wave （SAW）, the velocity of SAW is varied. Then the loading force can be introduced by effective material coefficients and the velocity of SAW is calculated via the general Green＇s Function. The experimental results accord with the above numerical calculation very well. It also shows that the propagation loss will increase with the force load, and the velocity variation of SAW is proportional to the force loaded to the surfaces of SAW resonators, which has a high sensitivity about 5.97 m/s·N.