The Scientific World Journal: Optics http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. A New Optical Surface Measurement Method with Iterative Sparsity-Constrained Threshold Phase Retrieval Algorithm Wed, 09 Apr 2014 12:05:26 +0000 http://www.hindawi.com/journals/tswj/2014/548395/ Due to its low complexity and acceptable accuracy, phase retrieval technique has been proposed as an alternative to solve the classic optical surface measurement task. However, to capture the overall wave field, phase retrieval based optical surface measurement (PROSM) system has to moderate the CCD position during the multiple-sampling procedure. The mechanical modules of CCD movement may bring about unexpectable deviation to the final results. To overcome this drawback, we propose a new PROSM method based on spatial light modulator (SLM). The mechanical CCD movement can be replaced by an electrical moderation of SLM patterns; thus the deviation can be significantly suppressed in the new PROSM method. In addition, to further improve the performance, we propose a new iterative threshold phase retrieval algorithm with sparsity-constraint to effectively reconstruct the phase of wave field. Experimental results show that the new method provides a more simple and robust solution for the optical surface measurement than the traditional techniques and achieves higher accuracy. Yi Niu, Yang Liu, Guangming Shi, Dahua Gao, and Guo Li Copyright © 2014 Yi Niu et al. All rights reserved. Interfacial Micromechanics in Fibrous Composites: Design, Evaluation, and Models Mon, 07 Apr 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/282436/ Recent advances of interfacial micromechanics in fiber reinforced composites using micro-Raman spectroscopy are given. The faced mechanical problems for interface design in fibrous composites are elaborated from three optimization ways: material, interface, and computation. Some reasons are depicted that the interfacial evaluation methods are difficult to guarantee the integrity, repeatability, and consistency. Micro-Raman study on the fiber interface failure behavior and the main interface mechanical problems in fibrous composites are summarized, including interfacial stress transfer, strength criterion of interface debonding and failure, fiber bridging, frictional slip, slip transition, and friction reloading. The theoretical models of above interface mechanical problems are given. Zhenkun Lei, Xuan Li, Fuyong Qin, and Wei Qiu Copyright © 2014 Zhenkun Lei et al. All rights reserved. A Real-Time Optical Tracking and Measurement Processing System for Flying Targets Wed, 02 Apr 2014 12:43:51 +0000 http://www.hindawi.com/journals/tswj/2014/976590/ Optical tracking and measurement for flying targets is unlike the close range photography under a controllable observation environment, which brings extreme conditions like diverse target changes as a result of high maneuver ability and long cruising range. This paper first designed and realized a distributed image interpretation and measurement processing system to achieve resource centralized management, multisite simultaneous interpretation and adaptive estimation algorithm selection; then proposed a real-time interpretation method which contains automatic foreground detection, online target tracking, multiple features location, and human guidance. An experiment is carried out at performance and efficiency evaluation of the method by semisynthetic video. The system can be used in the field of aerospace tests like target analysis including dynamic parameter, transient states, and optical physics characteristics, with security control. Pengyu Guo, Shaowen Ding, Hongliang Zhang, and Xiaohu Zhang Copyright © 2014 Pengyu Guo et al. All rights reserved. Narrow-Gap Semiconductors and Low-Dimensional Structures for Optoelectronic Applications Mon, 31 Mar 2014 10:12:15 +0000 http://www.hindawi.com/journals/tswj/2014/492521/ Fangyu Yue, Satyabrata Jit, and Weida Hu Copyright © 2014 Fangyu Yue et al. All rights reserved. Nanoscale Strain Fields Research of Boundaries between B2 Matrix and G.P. Zone in Ni-Ti Alloy Thin Films Mon, 24 Mar 2014 13:27:01 +0000 http://www.hindawi.com/journals/tswj/2014/127032/ Ti-47at.%Ni alloy films were prepared by magnetron sputtering followed by 460°C for 40 minutes heat-treatment. The strain fields between B2 phase matrix and G.P. zone were mapped by a combination of high-resolution transmission electron microscopy and geometric phase analysis method. It was found that there is a compressive strain region parallel to the longitudinal axis of G.P. zone with 2 nm in width, −2.2% in average strain at the boundaries between B2 phase and G.P. zone. Shilei Zhao and Chunwang Zhao Copyright © 2014 Shilei Zhao and Chunwang Zhao. All rights reserved. 3D Online Submicron Scale Observation of Mixed Metal Powder's Microstructure Evolution in High Temperature and Microwave Compound Fields Tue, 11 Mar 2014 13:16:12 +0000 http://www.hindawi.com/journals/tswj/2014/684081/ In order to study the influence on the mechanical properties caused by microstructure evolution of metal powder in extreme environment, 3D real-time observation of the microstructure evolution of Al-Ti mixed powder in high temperature and microwave compound fields was realized by using synchrotron radiation computerized topography (SR-CT) technique; the spatial resolution was enhanced to 0.37 μm/pixel through the designed equipment and the introduction of excellent reconstruction method for the first time. The process of microstructure evolution during sintering was clearly distinguished from 2D and 3D reconstructed images. Typical sintering parameters such as sintering neck size, porosity, and particle size of the sample were presented for quantitative analysis of the influence on the mechanical properties and the sintering kinetics during microwave sintering. The neck size-time curve was obtained and the neck growth exponent was 7.3, which indicated that surface diffusion was the main diffusion mechanism; the reason was the eddy current loss induced by the external microwave fields providing an additional driving force for mass diffusion on the particle surface. From the reconstructed images and the curve of porosity and average particle size versus temperature, it was believed that the presence of liquid phase aluminum accelerated the densification and particle growth. Dan Kang, Feng Xu, Xiao-fang Hu, Bo Dong, Yu Xiao, and Ti-qiao Xiao Copyright © 2014 Dan Kang et al. All rights reserved. In Situ Investigation of the 3D Mechanical Microstructure at Nanoscale: Nano-CT Imaging Method of Local Small Region in Large Scale Sample Thu, 27 Feb 2014 06:37:18 +0000 http://www.hindawi.com/journals/tswj/2014/806371/ To investigate the local micro-/nanoscale region in a large scale sample, an image reconstruction method for nanometer computed tomography (nano-CT) was proposed in this paper. In the algorithm, wavelets were used to localize the filtered-backprojection (FBP) algorithm because of its space-frequency localization property. After the implementation of the algorithm, two simulation local reconstruction experiments were performed to confirm its effectiveness. Three evaluation criteria were used in the experiments to judge the quality of the reconstructed images. The experimental results showed that the algorithm proposed in this paper performed best because (1) the quality of its results had improved 20%–30% compared to the results of FBP and 10%–30% compared to the results of another wavelet algorithm; (2) the new algorithm was stable under different circumstances. Besides, an actual reconstruction experiment was performed using real projection data that had been collected in a CT experiment. Two-dimensional (2D) and three-dimensional (3D) images of the sample were reconstructed. The microstructure of the sample could be clearly observed in the reconstructed images. Since much attention has been directed towards the nano-CT technique to investigate the microstructure of materials, this new wavelet-based local tomography algorithm could be considered as a meaningful effort. Bo Dong, Feng Xu, Xiao-fang Hu, Hong-yan Qu, Dan Kang, and Ti-qiao Xiao Copyright © 2014 Bo Dong et al. All rights reserved. Beta Value Coupled Wave Theory for Nonslanted Reflection Gratings Wed, 26 Feb 2014 12:11:30 +0000 http://www.hindawi.com/journals/tswj/2014/513734/ We present a modified coupled wave theory to describe the properties of nonslanted reflection volume diffraction gratings. The method is based on the beta value coupled wave theory, which will be corrected by using appropriate boundary conditions. The use of this correction allows predicting the efficiency of the reflected order for nonslanted reflection gratings embedded in two media with different refractive indices. The results obtained by using this method will be compared to those obtained using a matrix method, which gives exact solutions in terms of Mathieu functions, and also to Kogelnik’s coupled wave theory. As will be demonstrated, the technique presented in this paper means a significant improvement over Kogelnik’s coupled wave theory. Cristian Neipp, Jorge Francés, Sergi Gallego, Sergio Bleda, Francisco Javier Martínez, Inmaculada Pascual, and Augusto Beléndez Copyright © 2014 Cristian Neipp et al. All rights reserved. All-Optical 1-to-8 Wavelength Multicasting at 20 Gbit/s Exploiting Self-Phase Modulation in Dispersion Flattened Highly Nonlinear Photonic Crystal Fiber Mon, 24 Feb 2014 12:29:53 +0000 http://www.hindawi.com/journals/tswj/2014/828179/ All-optical multicasting of performing data routing from single node to multiple destinations in the optical domain is promising for next generation ultrahigh-peed photonic networks. Based on the self-phase modulation in dispersion flattened highly nonlinear photonic crystal fiber and followed spectral filtering, simultaneous 1-to-8 all-optical wavelength multicasting return-to-zero (RZ) signal at 20 Gbit/s with 100 GHz channel spaced is achieved. Wavelength tunable range and dynamic characteristic of proposed wavelength multicasting scheme is further investigated. The results show our designed scheme achieve operation wavelength range of 25 nm, OSNR of 32.01 dB and factor of 12.8. Moreover, the scheme has simple structure as well as high tolerance to signal power fluctuation. Zhan-Qiang Hui Copyright © 2014 Zhan-Qiang Hui. All rights reserved. High-Transmittance Subwavelength Metal Grating with Relief Structure Composed of Multiple Steps Tue, 18 Feb 2014 11:35:03 +0000 http://www.hindawi.com/journals/tswj/2014/495820/ A new kind of subwavelength metal grating with relief structure is designed and analyzed, in which the shape of the grating lines is no longer a single rectangle, but a relief structure with multiple steps. GsolverV52 was used to determine the optimal values of the grating period, groove depth, and the number of steps. The optical performance of the novel structure is evaluated and compared in terms of the transmission efficiency and extinction ratio over the visible and near-infrared wavelength spectrum. It is shown that, in the near-infrared band, the maximum transmittance can be increased about 15% compared to the traditional metal grating under the same parameters. With the unique characteristics, the metal grating is expected to find applications in liquid crystal display fields, polarization imaging, optical communication, and so on. Zhongfei Wang, Dawei Zhang, Qi Wang, Banglian Xu, Qingyong Tang, Yuanshen Huang, and Songlin Zhuang Copyright © 2014 Zhongfei Wang et al. All rights reserved. Automatic Three-Dimensional Measurement of Large-Scale Structure Based on Vision Metrology Mon, 17 Feb 2014 08:51:33 +0000 http://www.hindawi.com/journals/tswj/2014/185269/ All relevant key techniques involved in photogrammetric vision metrology for fully automatic 3D measurement of large-scale structure are studied. A new kind of coded target consisting of circular retroreflective discs is designed, and corresponding detection and recognition algorithms based on blob detection and clustering are presented. Then a three-stage strategy starting with view clustering is proposed to achieve automatic network orientation. As for matching of noncoded targets, the concept of matching path is proposed, and matches for each noncoded target are found by determination of the optimal matching path, based on a novel voting strategy, among all possible ones. Experiments on a fixed keel of airship have been conducted to verify the effectiveness and measuring accuracy of the proposed methods. Zhaokun Zhu, Banglei Guan, Xiaohu Zhang, Daokui Li, and Qifeng Yu Copyright © 2014 Zhaokun Zhu et al. All rights reserved. Second-Order Nonlinearity in Triangular Lattice Perforated Gold Film due to Surface Plasmas Resonance Sun, 16 Feb 2014 10:50:20 +0000 http://www.hindawi.com/journals/tswj/2014/284929/ We have studied the excitation second-order nonlinearity through a triangular lattice perforated gold film instead of square lattice in many papers. Under the excitation of surface plasmas resonance effect, the second order nonlinearity exists in the noncentrosymmetric split-ring resonators arrays. Reflection of fundamental frequency wave through a triangular lattice perforated gold film is obtained. We also described the second harmonic conversion efficiencies in the second order nonlinear optical process with the spectra. Moreover, the electric field distributions of fundamental frequency above the gold film region are calculated. The light propagation through the holes results in the enhancement of the second order nonlinearity including second harmonic generation as well as the sum (difference) frequency generation. Renlong Zhou, Xiaoshuang Chen, Yingyi Xiao, Bingju Zhou, Lingxi Wu, Xiaojuan Liu, Yongyi Gao, and Jie Zhan Copyright © 2014 Renlong Zhou et al. All rights reserved. Formation of Three-Way Scanning Electron Microscope Moiré on Micro/Nanostructures Tue, 11 Feb 2014 15:57:24 +0000 http://www.hindawi.com/journals/tswj/2014/281954/ Three-way scanning electron microscope (SEM) moiré was first generated using a designed three-way electron beam (EB) in an SEM. The spot-type three-way SEM moiré comes from the interference between the three-way EB and the specimen grating in which the periodic cells are arranged in a triangular manner. The deformation and the structure information of the specimen grating in three directions can be simultaneously obtained from the three-way SEM moiré. The design considerations of the three-way EB were discussed. As an illustration, the three-way SEM moiré spots produced on a silicon slide were presented. The proposed three-way SEM moiré method is expected to characterize micro/nanostructures in triangular or hexagonal arrangements in three directions at the same time. Qinghua Wang, Satoshi Kishimoto, and Hiroshi Tsuda Copyright © 2014 Qinghua Wang et al. All rights reserved. Strain Sensor of Carbon Nanotubes in Microscale: From Model to Metrology Mon, 10 Feb 2014 11:30:37 +0000 http://www.hindawi.com/journals/tswj/2014/406154/ A strain sensor composed of carbon nanotubes with Raman spectroscopy can achieve measurement of the three in-plane strain components in microscale. Based on previous work on the mathematic model of carbon nanotube strain sensors, this paper presents a detailed study on the optimization, diversification, and standardization of a CNT strain sensor from the viewpoint of metrology. A new miniaccessory for polarization control is designed, and two different preparing methods for CNT films as sensing media are introduced to provide diversified choices for applications. Then, the standard procedure of creating CNT strain sensors is proposed. Application experiments confirmed the effectiveness of the above improvement, which is helpful in developing this method for convenient metrology. Wei Qiu, Shi-Lei Li, Wei-lin Deng, Di Gao, and Yi-Lan Kang Copyright © 2014 Wei Qiu et al. All rights reserved. Fiber Optic Projection-Imaging System for Shape Measurement in Confined Space Mon, 10 Feb 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/206569/ A fiber-based projection-imaging system is proposed for shape measurement in confined space. Owing to the flexibility of imaging fibers, the system can be used in special scenarios that are difficult for conventional experimental setups. Three experiments: open space, closed space, and underwater are designed to demonstrate the strength and weakness of the system. It is shown that when proper alignment is possible, relatively high accuracy can be achieved; the error is less than 2% of the overall height of a specimen. In situations where alignment is difficult, significantly increased error is observed. The error is in the form of gross-scale geometrical distortion; for example, flat surface is reconstructed with curvature. In addition, the imaging fibers may introduce fine-scale noise into phase measurement, which has to be suppressed by smoothing filters. Based on results and analysis, it is found that although a fiber-based system has its unique strength, existing calibration and processing methods for fringe patterns have to be modified to overcome its drawbacks so as to accommodate wider applications. Lujie Chen, Viswanath Bavigadda, Theodoros Kofidis, and Robert D. Howe Copyright © 2014 Lujie Chen et al. All rights reserved. A Simulation Analysis of an Extension of One-Dimensional Speckle Correlation Method for Detection of General In-Plane Translation Thu, 30 Jan 2014 08:29:28 +0000 http://www.hindawi.com/journals/tswj/2014/704368/ The purpose of the study is to show a proposal of an extension of a one-dimensional speckle correlation method, which is primarily intended for determination of one-dimensional object's translation, for detection of general in-plane object's translation. In that view, a numerical simulation of a displacement of the speckle field as a consequence of general in-plane object's translation is presented. The translation components and representing the projections of a vector a of the object's displacement onto both - and -axes in the object plane are evaluated separately by means of the extended one-dimensional speckle correlation method. Moreover, one can perform a distinct optimization of the method by reduction of intensity values representing detected speckle patterns. The theoretical relations between the translation components and of the object and the displacement of the speckle pattern for selected geometrical arrangement are mentioned and used for the testifying of the proposed method's rightness. Ivana Hamarová, Petr Šmíd, Pavel Horváth, and Miroslav Hrabovský Copyright © 2014 Ivana Hamarová et al. All rights reserved. Study on Dielectric Function Models for Surface Plasmon Resonance Structure Thu, 30 Jan 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/503749/ The most common permittivity function models are compared and identifying the best model for further studies is desired. For this study, simulations using several different models and an analytical analysis on a practical surface Plasmon structure were done with an accuracy of ∼94.4% with respect to experimental data. Finite element method, combined with dielectric properties extracted from the Brendel-Bormann function model, was utilized, the latter being chosen from a comparative study on four available models. Peyman Jahanshahi, Mostafa Ghomeishi, and Faisal Rafiq Mahamd Adikan Copyright © 2014 Peyman Jahanshahi et al. All rights reserved. Valence Band Structure of and Alloy Semiconductors Calculated Using Valence Band Anticrossing Model Wed, 29 Jan 2014 13:11:02 +0000 http://www.hindawi.com/journals/tswj/2014/704830/ The valence band anticrossing model has been used to calculate the heavy/light hole and spin-orbit split-off energies in and alloy systems. It is found that both the heavy/light hole, and spin-orbit split levels move upwards in energy with an increase in Bi content in the alloy, whereas the split energy for the holes shows a reverse trend. The model is also used to calculate the reduction of band gap energy with an increase in Bi mole fraction. The calculated values of band gap variation agree well with the available experimental data. D. P. Samajdar and S. Dhar Copyright © 2014 D. P. Samajdar and S. Dhar. All rights reserved. Color Temperature Tunable White-Light LED Cluster with Extrahigh Color Rendering Index Thu, 23 Jan 2014 00:00:00 +0000 http://www.hindawi.com/journals/tswj/2014/897960/ The correlated color temperature (CCT) tunable white-light LED cluster with extrahigh color rendering property has been found by simulation and fabricated, which consists of three WW LEDs (CCT = 3183 K), one red LED (634.1 nm), one green LED (513.9 nm), and one blue LED (456.2 nm). The experimental results show that this cluster can realize the CCT tunable white-lights with a color rendering index (CRI) above 93, special CRI R9 for strong red above 90, average value of the special CRIs of R9 to R12 for the four saturated colors (red, yellow, green, and blue) above 83, and luminous efficacies above 70 lm/W at CCTs of 2719 K to 6497 K. Minhao Zhang, Yu Chen, and Guoxing He Copyright © 2014 Minhao Zhang et al. All rights reserved. Improved BDF Relaying Scheme Using Time Diversity over Atmospheric Turbulence and Misalignment Fading Channels Wed, 22 Jan 2014 13:26:55 +0000 http://www.hindawi.com/journals/tswj/2014/213834/ A novel bit-detect-and-forward (BDF) relaying scheme based on repetition coding with the relay is proposed, significantly improving the robustness to impairments proper to free-space optical (FSO) communications such as unsuitable alignment between transmitter and receiver as well as fluctuations in the irradiance of the transmitted optical beam due to the atmospheric turbulence. Closed-form asymptotic bit-error-rate (BER) expressions are derived for a 3-way FSO communication setup. Fully exploiting the potential time-diversity available in the relay turbulent channel, a relevant better performance is achieved, showing a greater robustness to the relay location since a high diversity gain is provided regardless of the source-destination link distance. Antonio García-Zambrana, Carmen Castillo-Vázquez, and Beatriz Castillo-Vázquez Copyright © 2014 Antonio García-Zambrana et al. All rights reserved. Quantum Key Based Burst Confidentiality in Optical Burst Switched Networks Wed, 22 Jan 2014 09:14:11 +0000 http://www.hindawi.com/journals/tswj/2014/786493/ The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS). This paper deals with employing RC4 (stream cipher) to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks. A. M. Balamurugan and A. Sivasubramanian Copyright © 2014 A. M. Balamurugan and A. Sivasubramanian. All rights reserved. Partially Coherent, Radially Polarized Beam with Annular Apodization Sun, 19 Jan 2014 07:26:18 +0000 http://www.hindawi.com/journals/tswj/2014/160945/ Based on the vectorial Debye theory, the tight focusing properties of partially coherent, radially polarized vortex beams are investigated in detail. In this paper, we propose to use an amplitude modulated filter in combination with a high NA lens to generate long focal depth in the focal region. Numerical results show that the generation of long focal depth of FWHM () is achieved, which finds useful application in microscopy techniques such as particle acceleration, laser processing, optical micromanipulation, and beam shaping. C. Mariyal, P. Suresh, K. B. Rajesh, and T. V. S. Pillai Copyright © 2014 C. Mariyal et al. All rights reserved. A Review of Refractometric Sensors Based on Long Period Fibre Gratings Wed, 18 Dec 2013 12:51:54 +0000 http://www.hindawi.com/journals/tswj/2013/913418/ In the last decade refractometric sensors have attracted an increasing interest by the scientific community due to their ability to perform ambient monitoring, to assess food quality and safety, and also to the fact that they enable the development of label free sensors in the biomedical area. These advances result, namely, from the use of long period fibre gratings in the turning points and/or with thin films in the transition region that allows resolutions of 10−6 to changes in the refractive index of the surrounding medium. Resolutions exceeding 10−8 can also be achieved when long period fibre gratings are combined with evanescent field based devices. This paper reviews the recent path towards the development of ultrahigh sensitive optical fibre refractometric sensors. G. Rego Copyright © 2013 G. Rego. All rights reserved. Effect of Same-Temperature GaN Cap Layer on the InGaN/GaN Multiquantum Well of Green Light-Emitting Diode on Silicon Substrate Wed, 04 Dec 2013 17:19:55 +0000 http://www.hindawi.com/journals/tswj/2013/538297/ GaN green LED was grown on Si (111) substrate by MOCVD. To enhance the quality of InGaN/GaN MQWs, same-temperature (ST) GaN protection layers with different thickness of 8 Å, 15 Å, and 30 Å were induced after the InGaN quantum wells (QWs) layer. Results show that a relative thicker cap layer is benefit to get InGaN QWs with higher In percent at fixed well temperature and obtain better QW/QB interface. As the cap thickness increases, the indium distribution becomes homogeneous as verified by fluorescence microscope (FLM). The interface of MQWs turns to be abrupt from XRD analysis. The intensity of photoluminescence (PL) spectrum is increased and the FWHM becomes narrow. Changda Zheng, Li Wang, Chunlan Mo, Wenqing Fang, and Fengyi Jiang Copyright © 2013 Changda Zheng et al. All rights reserved. Donor-Like Surface Traps on Two-Dimensional Electron Gas and Current Collapse of AlGaN/GaN HEMTs Mon, 18 Nov 2013 08:18:46 +0000 http://www.hindawi.com/journals/tswj/2013/931980/ The effect of donor-like surface traps on two-dimensional electron gas (2DEG) and drain current collapse of AlGaN/GaN high electron mobility transistors (HEMTs) has been investigated in detail. The depletion of 2DEG by the donor-like surface states is shown. The drain current collapse is found to be more sensitive to the addition of positive surface charges. Surface trap states with higher energy levels result in weaker current collapse and faster collapse process. By adopting an optimized backside doping scheme, the electron density of 2DEG has been improved greatly and the current collapse has been greatly eliminated. These results give reference to the improvement in device performance of AlGaN/GaN HEMTs. Chen-hui Yu, Qing-zhou Luo, Xiang-dong Luo, and Pei-sheng Liu Copyright © 2013 Chen-hui Yu et al. All rights reserved. Phosphorescent Molecularly Doped Light-Emitting Diodes with Blended Polymer Host and Wide Emission Spectra Wed, 13 Nov 2013 15:37:09 +0000 http://www.hindawi.com/journals/tswj/2013/954146/ Stable green light emission and high efficiency organic devices with three polymer layers were fabricated using bis[2-(4′-tert-butylphenyl)-1-phenyl-1H-benzoimidazole-N,C2′] iridium(III) (acetylacetonate) doped in blended host materials. The 1 wt% doping concentration showed maximum luminance of 7841 cd/cm2 at 25.6 V and maximum current efficiency of 9.95 cd/A at 17.2 V. The electroluminescence spectra of devices indicated two main peaks at 522 nm and 554 nm coming from phosphor dye and a full width at half maximum (FWHM) of 116 nm. The characteristics of using blended host, doping iridium complex, emission spectrum, and power efficiency of organic devices were investigated. Jun Wang, Jun Gou, and Weizhi Li Copyright © 2013 Jun Wang et al. All rights reserved. A Planar-Dimensions Machine Vision Measurement Method Based on Lens Distortion Correction Sun, 27 Oct 2013 16:12:05 +0000 http://www.hindawi.com/journals/tswj/2013/963621/ Lens distortion practically presents in a real optical imaging system causing nonuniform geometric distortion in the images and gives rise to additional errors in the vision measurement. In this paper, a planar-dimensions vision measurement method is proposed by improving camera calibration, in which the lens distortion is corrected on the pixel plane of image. The method can be divided into three steps: firstly, the feature points, only in the small central region of the image, are used to get a more accurate perspective projection model; secondly, rather than defining a uniform model, the smoothing spline function is used to describe the lens distortion in the measurement region of image, and two correction functions can be obtained by fitting two deviation surfaces; finally, a measurement method for planar dimensions is proposed, in which accurate magnification factor of imaging system can be obtained by using the correction functions. The effectiveness of the method is demonstrated by applying the proposed method to the test of measuring shaft diameter. Experimental data prove that the accurate planar-dimensions measurements can be performed using the proposed method even if images are deformed by lens distortion. Qiucheng Sun, Yueqian Hou, Qingchang Tan, and Guannan Li Copyright © 2013 Qiucheng Sun et al. All rights reserved. Uniformity Masks Design Method Based on the Shadow Matrix for Coating Materials with Different Condensation Characteristics Tue, 08 Oct 2013 08:28:44 +0000 http://www.hindawi.com/journals/tswj/2013/160792/ An intuitionistic method is proposed to design shadow masks to achieve thickness profile control for evaporation coating processes. The proposed method is based on the concept of the shadow matrix, which is a matrix that contains coefficients that build quantitive relations between shape parameters of masks and shadow quantities of substrate directly. By using the shadow matrix, shape parameters of shadow masks could be derived simply by solving a matrix equation. Verification experiments were performed on a special case where coating materials have different condensation characteristics. By using the designed mask pair with complementary shapes, thickness uniformities of better than 98% are demonstrated for MgF2 () and LaF3 () simultaneously on a 280 mm diameter spherical substrate with the radius curvature of 200 mm. Lichao Zhang and Xikun Cai Copyright © 2013 Lichao Zhang and Xikun Cai. All rights reserved. Optical Limiting Using the Two-Photon Absorption Electrical Modulation Effect in HgCdTe Photodiode Tue, 01 Oct 2013 15:28:23 +0000 http://www.hindawi.com/journals/tswj/2013/245310/ The electrical modulation properties of the output intensity of two-photon absorption (TPA) pumping were analyzed in this paper. The frequency dispersion dependence of TPA and the electric field dependence of TPA were calculated using Wherrett theory model and Garcia theory model, respectively. Both predicted a dramatic variation of TPA coefficient which was attributed into the increasing of the transition rate. The output intensity of the laser pulse propagation in the pn junction device was calculated by using function-transfer method. It shows that the output intensity increases nonlinearly with increasing intensity of incident light and eventually reaches saturation. The output saturation intensity depends on the electric field strength; the greater the electric field, the smaller the output intensity. Consequently, the clamped saturation intensity can be controlled by the electric field. The prior advantage of electrical modulation is that the TPA can be varied extremely continuously, thus adjusting the output intensity in a wide range. This large change provides a manipulate method to control steady output intensity of TPA by adjusting electric field. Haoyang Cui, Junjie Yang, Jundong Zeng, and Zhong Tang Copyright © 2013 Haoyang Cui et al. All rights reserved. The Effect of Metal-Semiconductor Contact on the Transient Photovoltaic Characteristic of HgCdTe PV Detector Mon, 30 Sep 2013 08:23:52 +0000 http://www.hindawi.com/journals/tswj/2013/213091/ The transient photovoltaic (PV) characteristic of HgCdTe PV array is studied using an ultrafast laser. The photoresponse shows an apparent negative valley first, then it evolves into a positive peak. By employing a combined theoretical model of pn junction and Schottky potential, this photo-response polarity changing curves can be interpreted well. An obvious decreasing of ratio of negative valley to positive peak can be realized by limiting the illumination area of the array electrode. This shows that the photoelectric effect of Schottky barrier at metal-semiconductor (M/S) interface is suppressed, which will verify the correctness of the model. The characteristic parameters of transient photo-response induced from p-n junction and Schottky potential are extracted by fitting the response curve utilizing this model. It shows that the negative PV response induced by the Schottky barrier decreases the positive photovoltage generated by the pn junction. Haoyang Cui, Yongpeng Xu, Junjie Yang, Naiyun Tang, and Zhong Tang Copyright © 2013 Haoyang Cui et al. All rights reserved. Quantum Control and Quantum Information Technology Thu, 19 Sep 2013 11:36:17 +0000 http://www.hindawi.com/journals/tswj/2013/525631/ Daoyi Dong, Chunlin Chen, Min Jiang, and Lin-Cheng Wang Copyright © 2013 Daoyi Dong et al. All rights reserved. Study on the Effect of Blood Content on Diffuse Reflectance Spectra of Basal Cell Carcinoma Skin Tissue Mon, 19 Aug 2013 08:57:39 +0000 http://www.hindawi.com/journals/tswj/2013/192495/ Diffuse reflectance spectrum as a noninvasive method has been widely used to study the optical properties of cutaneous skin tissue. In this work, we optimized an eight-layered optical model of basal cell carcinoma skin tissue to study its optical properties. Based on the model, the diffuse reflectance spectra were reconstructed in visible wavelength range by Monte Carlo methods. After different blood contents were added to the optical model, the contribution of blood to diffuese reflectance spectra was investigated theoretically. The ratios of basal cell carcinoma skin and normal skin tissue were also calculated for both experimental result and rebuilt results to testify the theoretical reasonability of the model and methods. Miaoqing Nan and Qingli He Copyright © 2013 Miaoqing Nan and Qingli He. All rights reserved. Closed-Loop and Robust Control of Quantum Systems Wed, 07 Aug 2013 11:44:54 +0000 http://www.hindawi.com/journals/tswj/2013/869285/ For most practical quantum control systems, it is important and difficult to attain robustness and reliability due to unavoidable uncertainties in the system dynamics or models. Three kinds of typical approaches (e.g., closed-loop learning control, feedback control, and robust control) have been proved to be effective to solve these problems. This work presents a self-contained survey on the closed-loop and robust control of quantum systems, as well as a brief introduction to a selection of basic theories and methods in this research area, to provide interested readers with a general idea for further studies. In the area of closed-loop learning control of quantum systems, we survey and introduce such learning control methods as gradient-based methods, genetic algorithms (GA), and reinforcement learning (RL) methods from a unified point of view of exploring the quantum control landscapes. For the feedback control approach, the paper surveys three control strategies including Lyapunov control, measurement-based control, and coherent-feedback control. Then such topics in the field of quantum robust control as control, sliding mode control, quantum risk-sensitive control, and quantum ensemble control are reviewed. The paper concludes with a perspective of future research directions that are likely to attract more attention. Chunlin Chen, Lin-Cheng Wang, and Yuanlong Wang Copyright © 2013 Chunlin Chen et al. All rights reserved. Optimal Design of an Ultrasmall SOI-Based 1 × 8 Flat-Top AWG by Using an MMI Wed, 31 Jul 2013 09:15:43 +0000 http://www.hindawi.com/journals/tswj/2013/636912/ Four methods based on a multimode interference (MMI) structure are optimally designed to flatten the spectral response of silicon-on-insulator- (SOI-) based arrayed-waveguide grating (AWG) applied in a demodulation integration microsystem. In the design for each method, SOI is selected as the material, the beam propagation method is used, and the performances (including the 3 dB passband width, the crosstalk, and the insertion loss) of the flat-top AWG are studied. Moreover, the output spectrum responses of AWGs with or without a flattened structure are compared. The results show that low insertion loss, crosstalk, and a flat and efficient spectral response are simultaneously achieved for each kind of structure. By comparing the four designs, the design that combines a tapered MMI with tapered input/output waveguides, which has not been previously reported, was shown to yield better results than others. The optimized design reduced crosstalk to approximately −21.9 dB and had an insertion loss of −4.36 dB and a 3 dB passband width, that is, approximately 65% of the channel spacing. Hongqiang Li, Yaoting Bai, Xiaye Dong, Enbang Li, Yang Li, Yu Liu, and Wenqian Zhou Copyright © 2013 Hongqiang Li et al. All rights reserved. Calculating the Energy Spectrum of Complex Low-Dimensional Heterostructures in the Electric Field Thu, 18 Jul 2013 11:53:39 +0000 http://www.hindawi.com/journals/tswj/2013/807462/ An algorithm for solving the steady-state Schrödinger equation for a complex piecewise-constant potential in the presence of the -field is developed and implemented. The algorithm is based on the consecutive matching of solutions given by the Airy functions at the band boundaries with the matrix rank increasing by no more than two orders, which enables the characteristic solution to be obtained in the convenient form for search of the roots. The algorithm developed allows valid solutions to be obtained for the electric field magnitudes larger than the ground-state energy level, that is, when the perturbation method is not suitable. Svetlana N. Khonina, Sergey G. Volotovsky, Sergey I. Kharitonov, and Nikolay L. Kazanskiy Copyright © 2013 Svetlana N. Khonina et al. All rights reserved. Stress and Temperature Sensitivity of Photonic Crystals Resonant Cavity Tue, 09 Jul 2013 10:25:50 +0000 http://www.hindawi.com/journals/tswj/2013/805470/ The temperature and stress characteristic of photonic band gap structure resonant cavities with square and graphite lattice have been studied by finite-difference time-domain method. The results show that the resonant cavities, both square and graphite lattice, have more and more resonant frequency with the cavity enlarging. And the curves between the resonant frequency and stress have better linearity. When the cavity enlarges enough, the curve between resonant frequency and temperature will become sectionalized line from nonlinear curve. Especially, the temperature sensitivity will be descending as the cavity is enlarging. Nevertheless, once some structures are put in the center of the cavity, the temperature sensitivity will be rising fast for this kind of cavity. Obviously, this character is convenient for us to achieve the specification measurement for temperature and stress. Yan Li, Xue Zhao, Xiao-li Li, and Hai-wei Fu Copyright © 2013 Yan Li et al. All rights reserved. Small Obstacle Avoidance Sensor Tue, 25 Jun 2013 12:12:09 +0000 http://www.hindawi.com/journals/tswj/2013/604538/ This paper describes a laser ranging sensor that is suitable for applications like small unmanned aerial vehicles. The hardware consists of a diode emitter array and line-scan charge coupled devices. A structured-light technique measures ranges up to 30 meters for 64 field angles in a 90 degree field of view. Operation is eye safe, and the laser wavelength is not visible to night vision goggles. This paper describes a specific sensor design in order to illustrate performance for a given package size. Richard H. Vollmerhausen Copyright © 2013 Richard H. Vollmerhausen. All rights reserved. Timing and Operating Mode Design for Time-Gated Fluorescence Lifetime Imaging Microscopy Mon, 24 Jun 2013 07:57:17 +0000 http://www.hindawi.com/journals/tswj/2013/801901/ Steady-state fluorence imaging and time-resolved fluorescence imaging are two important areas in fluorescence imaging research. Fluorescence lifetime imaging is an absolute measurement method which is independent of excitation laser intensity, fluorophore concentration, and photobleaching compared to fluorescence intensity imaging techniques. Time-gated fluorescence lifetime imaging microscopy (FLIM) can provide high resolution and high imaging frame during mature FLIM methods. An abstract time-gated FLIM model was given, and important temporal parameters are shown as well. Aiming at different applications of steady and transient fluorescence processes, two different operation modes, timing and lifetime computing algorithm are designed. High resolution and high frame can be achieved by one-excitation one-sampling mode and least square algorithm for steady imaging applications. Correspondingly, one-excitation two-sampling mode and rapid lifetime determination algorithm contribute to transient fluorescence situations. Chao Liu, Xinwei Wang, Yan Zhou, and Yuliang Liu Copyright © 2013 Chao Liu et al. All rights reserved. Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements Thu, 20 Jun 2013 17:09:08 +0000 http://www.hindawi.com/journals/tswj/2013/127670/ New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications. R. A. Ganeev Copyright © 2013 R. A. Ganeev. All rights reserved. Controlling the Shannon Entropy of Quantum Systems Thu, 30 May 2013 15:52:59 +0000 http://www.hindawi.com/journals/tswj/2013/381219/ This paper proposes a new quantum control method which controls the Shannon entropy of quantum systems. For both discrete and continuous entropies, controller design methods are proposed based on probability density function control, which can drive the quantum state to any target state. To drive the entropy to any target at any prespecified time, another discretization method is proposed for the discrete entropy case, and the conditions under which the entropy can be increased or decreased are discussed. Simulations are done on both two- and three-dimensional quantum systems, where division and prediction are used to achieve more accurate tracking. Yifan Xing and Jun Wu Copyright © 2013 Yifan Xing and Jun Wu. All rights reserved. The Effects of Five-Order Nonlinear on the Dynamics of Dark Solitons in Optical Fiber Thu, 30 May 2013 09:25:32 +0000 http://www.hindawi.com/journals/tswj/2013/130734/ We study the influence of five-order nonlinear on the dynamic of dark soliton. Starting from the cubic-quintic nonlinear Schrodinger equation with the quadratic phase chirp term, by using a similarity transformation technique, we give the exact solution of dark soliton and calculate the precise expressions of dark soliton's width, amplitude, wave central position, and wave velocity which can describe the dynamic behavior of soliton's evolution. From two different kinds of quadratic phase chirps, we mainly analyze the effect on dark soliton’s dynamics which different fiver-order nonlinear term generates. The results show the following two points with quintic nonlinearities coefficient increasing: (1) if the coefficients of the quadratic phase chirp term relate to the propagation distance, the solitary wave displays a periodic change and the soliton’s width increases, while its amplitude and wave velocity reduce. (2) If the coefficients of the quadratic phase chirp term do not depend on propagation distance, the wave function only emerges in a fixed area. The soliton’s width increases, while its amplitude and the wave velocity reduce. Feng-Tao He, Xiao-Lin Wang, and Zuo-Liang Duan Copyright © 2013 Feng-Tao He et al. All rights reserved. Hybrid Impulsive Control for Closed Quantum Systems Tue, 28 May 2013 15:52:41 +0000 http://www.hindawi.com/journals/tswj/2013/545091/ The state transfer problem of a class of nonideal quantum systems is investigated. It is known that traditional Lyapunov methods may fail to guarantee convergence for the nonideal case. Hence, a hybrid impulsive control is proposed to accomplish a more accurate convergence. In particular, the largest invariant sets are explicitly characterized, and the convergence of quantum impulsive control systems is analyzed accordingly. Numerical simulation is also presented to demonstrate the improvement of the control performance. Shouwei Zhao, Jitao Sun, and Hai Lin Copyright © 2013 Shouwei Zhao et al. All rights reserved. Simulation of Quantum Dynamics Based on the Quantum Stochastic Differential Equation Tue, 28 May 2013 08:10:43 +0000 http://www.hindawi.com/journals/tswj/2013/424137/ The quantum stochastic differential equation derived from the Lindblad form quantum master equation is investigated. The general formulation in terms of environment operators representing the quantum state diffusion is given. The numerical simulation algorithm of stochastic process of direct photodetection of a driven two-level system for the predictions of the dynamical behavior is proposed. The effectiveness and superiority of the algorithm are verified by the performance analysis of the accuracy and the computational cost in comparison with the classical Runge-Kutta algorithm. Ming Li Copyright © 2013 Ming Li. All rights reserved. A Coherence Preservation Control Strategy in Cavity QED Based on Classical Quantum Feedback Tue, 28 May 2013 08:08:34 +0000 http://www.hindawi.com/journals/tswj/2013/340917/ For eliminating the unexpected decoherence effect in cavity quantum electrodynamics (cavity QED), the transfer function of Rabi oscillation is derived theoretically using optical Bloch equations. In particular, the decoherence in cavity QED from the atomic spontaneous emission is especially considered. A feedback control strategy is proposed to preserve the coherence through Rabi oscillation stabilization. In the scheme, a classical quantum feedback channel for the quantum information acquisition is constructed via the quantum tomography technology, and a compensation system based on the root locus theory is put forward to suppress the atomic spontaneous emission and the associated decoherence. The simulation results have proved its effectiveness and superiority for the coherence preservation. Ming Li, Wei Chen, and Junli Gao Copyright © 2013 Ming Li et al. All rights reserved. A Survey of Quantum Lyapunov Control Methods Mon, 27 May 2013 17:01:41 +0000 http://www.hindawi.com/journals/tswj/2013/967529/ The condition of a quantum Lyapunov-based control which can be well used in a closed quantum system is that the method can make the system convergent but not just stable. In the convergence study of the quantum Lyapunov control, two situations are classified: nondegenerate cases and degenerate cases. For these two situations, respectively, in this paper the target state is divided into four categories: the eigenstate, the mixed state which commutes with the internal Hamiltonian, the superposition state, and the mixed state which does not commute with the internal Hamiltonian. For these four categories, the quantum Lyapunov control methods for the closed quantum systems are summarized and analyzed. Particularly, the convergence of the control system to the different target states is reviewed, and how to make the convergence conditions be satisfied is summarized and analyzed. Shuang Cong and Fangfang Meng Copyright © 2013 Shuang Cong and Fangfang Meng. All rights reserved. High Sensitivity Optically Pumped Quantum Magnetometer Sun, 26 May 2013 18:37:28 +0000 http://www.hindawi.com/journals/tswj/2013/858379/ Quantum magnetometers based on optical pumping can achieve sensitivity as high as what SQUID-based devices can attain. In this paper, we discuss the principle of operation and the optimal design of an optically pumped quantum magnetometer. The ultimate intrinsic sensitivity is calculated showing that optimal performance of the magnetometer is attained with an optical pump power of 20 μW and an operation temperature of 48°C. Results show that the ultimate intrinsic sensitivity of the quantum magnetometer that can be achieved is 327 fT/Hz1/2 over a bandwidth of 26 Hz and that this sensitivity drops to 130 pT/Hz1/2 in the presence of environmental noise. The quantum magnetometer is shown to be capable of detecting a sinusoidal magnetic field of amplitude as low as 15 pT oscillating at 25 Hz. Valentina Tiporlini and Kamal Alameh Copyright © 2013 Valentina Tiporlini and Kamal Alameh. All rights reserved. Uniform Diffracted Fields from a Perfectly Conducting Cylindrical Reflector with Modified Theory of Physical Optics Sun, 26 May 2013 18:33:13 +0000 http://www.hindawi.com/journals/tswj/2013/195402/ The uniform diffracted fields are calculated on PEC cylindrical reflector by Modified Theory of Physical Optics (MTPO). It is aimed to convert the noncontinuous solution to a continuous solution by finding a uniform equation which does not contain any expression converging to 0 in the denominator part. Three axioms of MTPO theory are used to construct the integral equations for the perfectly electrically conducting surface application. The “edge-point” technique is used to find the diffracted field, and uniform solution is to be found via “detour parameter(s).” Finally, the obtained results are to be compared with the nonuniform ones, numerically. Uğur Yalçın and Mücahit Sarnık Copyright © 2013 Uğur Yalçın and Mücahit Sarnık. All rights reserved. Lyapunov Control of Quantum Systems with Impulsive Control Fields Tue, 21 May 2013 10:04:46 +0000 http://www.hindawi.com/journals/tswj/2013/814080/ We investigate the Lyapunov control of finite-dimensional quantum systems with impulsive control fields, where the studied quantum systems are governed by the Schrödinger equation. By three different Lyapunov functions and the invariant principle of impulsive systems, we study the convergence of quantum systems with impulsive control fields and propose new results for the mentioned quantum systems in the form of sufficient conditions. Two numerical simulations are presented to illustrate the effectiveness of the proposed control method. Wei Yang and Jitao Sun Copyright © 2013 Wei Yang and Jitao Sun. All rights reserved. A Fast and Efficient Adaptive Threshold Rate Control Scheme for Remote Sensing Images Sun, 11 Nov 2012 12:54:42 +0000 http://www.hindawi.com/journals/tswj/2012/691413/ The JPEG2000 image compression standard is ideal for processing remote sensing images. However, its algorithm is complex and it requires large amounts of memory, making it difficult to adapt to the limited transmission and storage resources necessary for remote sensing images. In the present study, an improved rate control algorithm for remote sensing images is proposed. The required coded blocks are sorted downward according to their numbers of bit planes prior to entropy coding. An adaptive threshold computed from the combination of the minimum number of bit planes, along with the minimum rate-distortion slope and the compression ratio, is used to truncate passes of each code block during Tier-1 encoding. This routine avoids the encoding of all code passes and improves the coding efficiency. The simulation results show that the computational cost and working buffer memory size of the proposed algorithm reach only 18.13 and 7.81%, respectively, of the same parameters in the postcompression rate distortion algorithm, while the peak signal-to-noise ratio across the images remains almost the same. The proposed algorithm not only greatly reduces the code complexity and buffer requirements but also maintains the image quality. Xiao Chen and Xiaoqing Xu Copyright © 2012 Xiao Chen and Xiaoqing Xu. All rights reserved.