Advances in OptoElectronics The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. A Grooming Nodes Optimal Allocation Method for Multicast in WDM Networks Thu, 18 Feb 2016 10:47:48 +0000 The grooming node has the capability of grooming multicast traffic with the small granularity into established light at high cost of complexity and node architecture. In the paper, a grooming nodes optimal allocation (GNOA) method is proposed to optimize the allocation of the grooming nodes constraint by the blocking probability for multicast traffic in sparse WDM networks. In the proposed GNOA method, the location of each grooming node is determined by the SCLD strategy. The improved smallest cost largest degree (SCLD) strategy is designed to select the nongrooming nodes in the proposed GNOA method. The simulation results show that the proposed GNOA method can reduce the required number of grooming nodes and decrease the cost of constructing a network to guarantee a certain request blocking probability when the wavelengths per fiber and transmitter/receiver ports per node are sufficient for the optical multicast in WDM networks. Chengying Wei, Qinren Shen, Huanlin Liu, and Yong Chen Copyright © 2016 Chengying Wei et al. All rights reserved. Physics of Internal Photoemission and Its Infrared Applications in the Low-Energy Limit Thu, 28 Jan 2016 11:17:35 +0000 Internal photoemission (IP) correlates with processes in which carriers are photoexcited and transferred from one material to another. This characteristic allows characterizing the properties of the heterostructure, for example, the band parameters of a material and the interface between two materials. IP also involves the generation and collection of photocarriers, which leads to applications in the photodetectors. This review discusses the generic IP processes based on heterojunction structures, characterizing -type band structure and the band offset at the heterointerface, and infrared photodetection including a novel concept of photoresponse extension based on an energy transfer mechanism between hot and cold carriers. Y. F. Lao and A. G. U. Perera Copyright © 2016 Y. F. Lao and A. G. U. Perera. All rights reserved. Mathematical Verification for Transmission Performance of Centralized Lightwave WDM-RoF-PON with Quintuple Services Integrated in Each Wavelength Channel Tue, 29 Dec 2015 11:36:15 +0000 Wavelength-division-multiplexing passive-optical-network (WDM-PON) has been recognized as a promising solution of the “last mile” access as well as multibroadband data services access for end users, and WDM-RoF-PON, which employs radio-over-fiber (RoF) technique in WDM-PON, is even a more attractive approach for future broadband fiber and wireless access for its strong availability of centralized multiservices transmission operation and its transparency for bandwidth and signal modulation formats. As for multiservices development in WDM-RoF-PON, various system designs have been reported and verified via simulation or experiment till now, and the scheme with multiservices transmitted in each single wavelength channel is believed as the one that has the highest bandwidth efficiency; however, the corresponding mathematical verification is still hard to be found in state-of-the-art literature. In this paper, system design and data transmission performance of a quintuple services integrated WDM-RoF-PON which jointly employs carrier multiplexing and orthogonal modulation techniques, have been theoretically analyzed and verified in detail; moreover, the system design has been duplicated and verified experimentally and the theory system of such WDM-RoF-PON scheme has thus been formed. Shuai Chen, Wei Nai, Fangqi Zhang, Shaoyin Wang, Decun Dong, and Yi Yu Copyright © 2015 Shuai Chen et al. All rights reserved. Target Tracking Algorithm Using Angular Point Matching Combined with Compressive Tracking Tue, 10 Nov 2015 07:06:20 +0000 To solve the problems of tracking errors such as target missing that emerged in compressive tracking (CT) algorithm due to factors such as pose variation, illumination change, and occlusion, a novel tracking algorithm combined angular point matching with compressive tracking (APMCCT) was proposed. A sparse measurement matrix was adopted to extract the Haar-like features. The offset of the predicted target position was integrated into the angular point matching, and the new target position was calculated. Furthermore, the updating mechanism of the template was optimized. Experiments on different video sequences have shown that the proposed APMCCT performs better than CT algorithm in terms of accuracy and robustness and adaptability to pose variation, illumination change, and occlusion. Jing Luo, Tingting Dong, Chunyuan Zi, Chunbo Xiu, Huixin Tian, and Jiangtao Xi Copyright © 2015 Jing Luo et al. All rights reserved. All-Optical Surface Micropatterning by Electric Field Intensity Gradient Thu, 05 Nov 2015 07:47:47 +0000 In this report an all-optical photo-induced formation of surface relief gratings is shown. For the surface patterning of As2S3 and As4S1.5Se4.5 films a direct holographic recording setup with a 532 nm wavelength Nd:YAG CW laser light was used. Our investigations have shown that the light-induced mass transfer process strongly depends on the material itself and on the polarization of the light. It has been shown that an electric field intensity gradient has to be obtained to achieve a direct patterning. The evolution of a surface relief in relation to recording parameters and thickness of the sample has been investigated in detail. U. Gertners and J. Teteris Copyright © 2015 U. Gertners and J. Teteris. All rights reserved. Analysis of the Interference Modulation Depth in the Fourier Transform Spectrometer Sun, 04 Oct 2015 16:34:22 +0000 Based on the principle of the Michelson interferometer, the paper briefly describes the theoretical significance and calculates and deduces three expressions of the interference modulation depth. The influence of the surface shape error of plane mirror on modulation depth is analyzed, and the tolerance of error is also pointed out. Moreover, the dependence of modulation depth on the reflectance change of beam splitter interface is also analyzed, and the curve is given. It is concluded that this paper is of general significance for the Fourier transform spectrometer based on the principle of the Michelson two-beam interference. Rilong Liu Copyright © 2015 Rilong Liu. All rights reserved. Effective Evaluation of the Noise Factor of Microchannel Plate Thu, 27 Aug 2015 06:13:40 +0000 To improve the noise performance of microchannel plate (MCP), we have presented a method using the sine random signals with Poisson distribution as the noise-excitation for electron source. By using this method, the effective evaluation of noise characteristics of MCP has been implemented through measuring and analyzing its noise factor. The results have demonstrated that the noise factor of filmed MCP is lower than 1.8. Additionally, as the open area ratio and the input electron energy are 72% and 400 eV, respectively, the noise characteristics of unfilmed MCP are improved evidently. Moreover, larger open area ratio, higher input electron energy, and higher voltage across the MCP all can reduce effectively the noise factor within a certain range. Meanwhile, the ion barrier film extends the life of image tube but at the cost of an increased noise factor. Therefore, it is necessary that a compromise between the optimum thickness of ion barrier film, open area ratio, input electron energy, and voltage across the MCP must be reached. Honggang Wang, Yujie Du, Yu Feng, Yang Lv, Xiaoming Hu, and Yunsheng Qian Copyright © 2015 Honggang Wang et al. All rights reserved. Gain Incorporated Split-Ring Resonator Structures for Active Metamaterials Wed, 26 Aug 2015 14:19:43 +0000 We present a systematic study of split-ring resonator (SRR) structures that are used as the basic building blocks of active metamaterials with incorporated gain. The active split-ring resonator (aSRR) structures with gain elements can in theory have similar unusual electromagnetic responses such as negative effective permeability near their resonance of the artificial magnetic response just like their passive counterparts. At the same time aSRRs can have reversed imaginary part of the effective permeability and, therefore, mitigate the loss of passive SRRs. We explored in detail both passive and active SRRs through analytic theory, numerical simulations, and lab experimentation and demonstrated that aSRRs can have the similar negative effective permeability responses while reducing and even reversing the loss. Jordan Chaires, David Schumerth, Cole Drawdy, and Weiguo Yang Copyright © 2015 Jordan Chaires et al. All rights reserved. Fivefold Symmetric Photonic Quasi-Crystal Fiber for Dispersion Compensation from S- to L-Band and Optimized at 1.55 μm Mon, 03 Aug 2015 14:20:46 +0000 A highly dispersive dual core quasi-periodic photonic crystal fiber is proposed for chromatic dispersion compensation. The dispersion for the dual concentric core fiber is optimized to compensate the chromatic dispersion with a high negative dispersion, accomplishing the communication bandwidth from S-band (1460 nm) to L-band (1625 nm). By precise control of structural parameter we have achieved a maximum dispersion of −18,838 ps/nm-km with the phase matching wavelength centred around 1.55 μm. We also numerically investigate the influence of structural parameter and doping effects and its response on peak dispersion parameter. Sivacoumar Rajalingam and Zachariah C. Alex Copyright © 2015 Sivacoumar Rajalingam and Zachariah C. Alex. All rights reserved. Optimization of Multiband White-Light Illuminants for Specified Color Temperatures Mon, 25 May 2015 11:10:53 +0000 This paper describes an effective approach for the optimization of multiband spectra to produce prospective white-light spectra having specific color temperatures. The optimization process employs a genetic algorithm known as differential evolution, which aims to minimize the color rendering differences between a prospective white-light spectrum and its corresponding reference illuminant. Color rendering is assessed by calculating the CIEDE2000 color difference (ΔE00) for 14 CIE test colors under the two sources. Optimized white-light spectra were matched to three CIE standard illuminants, that is, A (2856 K), D50 (5003 K), and D65 (6504 K). Optimal solutions for three- and four-band 25 and 50 nm Gaussian spectra are presented and analyzed, together with mixed 4-LED spectra that were optimized in the same way. In all cases, the simulated sources were shown to provide color rendering of such quality that ΔE00av ≤ 2.24 units. Such white-light sources would likely find wide acceptance in numerous lighting applications. Snjezana Soltic and Andrew Neil Chalmers Copyright © 2015 Snjezana Soltic and Andrew Neil Chalmers. All rights reserved. Block-Based Compressed Sensing for Neutron Radiation Image Using WDFB Thu, 02 Apr 2015 14:11:34 +0000 An ideal compression method for neutron radiation image should have high compression ratio while keeping more details of the original image. Compressed sensing (CS), which can break through the restrictions of sampling theorem, is likely to offer an efficient compression scheme for the neutron radiation image. Combining wavelet transform with directional filter banks, a novel nonredundant multiscale geometry analysis transform named Wavelet Directional Filter Banks (WDFB) is constructed and applied to represent neutron radiation image sparsely. Then, the block-based CS technique is introduced and a high performance CS scheme for neutron radiation image is proposed. By performing two-step iterative shrinkage algorithm the problem of norm minimization is solved to reconstruct neutron radiation image from random measurements. The experiment results demonstrate that the scheme not only improves the quality of reconstructed image obviously but also retains more details of original image. Wei Jin, Zhen Liu, and Gang Li Copyright © 2015 Wei Jin et al. All rights reserved. Unusual Blueshifting of Optical Band Gap of CdS Nanocrystals through a Chemical Bath Deposition Method Thu, 05 Mar 2015 12:04:57 +0000 CdS nanocrystals are synthesized through a chemical bath deposition method. After annealing, these nanocrystals are enlarged according to Scherrer’s formula. Small nanocrystals display wide band gaps as a result of the quantum effect experienced by nanocrystals of a certain size. However, the absorption edge and green and red emissions of annealed CdS nanocrystals show obvious blueshift compared with the as-grown ones. After annealing, the intensity ratio of these green and red emissions increases, which indicated that the defect states are reduced. Therefore, the improvement in crystalline quality and the reduced strain contribute to the unusual blueshifting of the optical band gap and of the green and red emissions. Shu Qing Yuan, Peng Fei Ji, Yong Li, Yue Li Song, and Feng Qun Zhou Copyright © 2015 Shu Qing Yuan et al. All rights reserved. A Microring Temperature Sensor Based on the Surface Plasmon Wave Sun, 15 Feb 2015 09:13:17 +0000 A structure of microring sensor suitable for temperature measurement based on the surface plasmon wave is put forward in this paper. The sensor uses surface plasmon multilayer waveguiding structure in the vertical direction and U-shaped microring structure in the horizontal direction and utilizes SOI as the thermal material. The transfer function derivation of the structure of surface plasmon microring sensor is according to the transfer matrix method. While the change of refractive index of Si is caused by the change of ambient temperature, the effective refractive index of the multilayer waveguiding structure is changed, resulting in the drifting of the sensor output spectrum. This paper focuses on the transmission characteristics of multilayer waveguide structure and the impact on the output spectrum caused by refractive index changes in temperature parts. According to the calculation and simulation, the transmission performance of the structure is stable and the sensitivity is good. The resonance wavelength shift can reach 0.007 μm when the temperature is increased by 100 k and FSR can reach about 60 nm. This structure achieves a high sensitivity in the temperature sense taking into account a wide range of filter frequency selections, providing a theoretical basis for the preparation of microoptics. Wenchao Li, Xiaopeng Sha, Dongyang An, and Zhiquan Li Copyright © 2015 Wenchao Li et al. All rights reserved. Performance of Series Connected GaAs Photovoltaic Converters under Multimode Optical Fiber Illumination Sun, 21 Dec 2014 00:10:03 +0000 In many military and industrial applications, GaAs photovoltaic (PV) converters are connected in series in order to generate the required voltage compatible with most common electronics. Multimode optical fibers are usually used to carry high-intensity laser and illuminate the series connected GaAs PV converters in real time. However, multimode optical fiber illumination has a speckled intensity pattern. The series connected PV array is extremely sensitive to nonuniform illumination; its performance is limited severely by the converter that is illuminated the least. This paper quantifies the effects of multimode optical fiber illumination on the performance of series connected GaAs PV converters, analyzes the loss mechanisms due to speckles, and discusses the maximum illumination efficiency. In order to describe the illumination dependent behavior detailedly, modeling of the series connected PV array is accomplished based on the equivalent circuit for PV cells. Finally, a series of experiments are carried out to demonstrate the theory analysis. Tiqiang Shan and Xinglin Qi Copyright © 2014 Tiqiang Shan and Xinglin Qi. All rights reserved. Preparation of Compensation Ions Codoped SrTiO3:Pr3+ Red Phosphor with the Sol-Gel Method and Study of Its Luminescence Enhancement Mechanism Sun, 14 Dec 2014 07:22:32 +0000 SrTiO3:Pr3+ is the most representative titanate matrix red phosphor for field emission display (FED). The red luminous efficiency of SrTiO3:Pr3+ will be greatly improved after the compensation ions codoping, so SrTiO3:Pr3+ red phosphor has been a research focus at home and abroad. SrTiO3:Pr3+, SrTiO3:Pr3+, Mg2+, and SrTiO3:Pr3+, Al3+ phosphors are synthesized by a new sol-gel method. Crystal structure, spectral characteristics, and luminescence enhancement mechanism of the sample were studied by XRD and PL spectra. The results showed that after co-doped, SrTiO3:Pr3+ phosphor is single SrTiO3 cubic phase, the main emission front is located at 614 nm, corresponding to Pr3+ ions 1D23H4 transition emission. SrTiO3:Pr3+, Mg2+ and SrTiO3:Pr3+, Al3+ phosphor luminescence intensity is enhanced, but the main luminescence mechanism is not changed. Acceptor impurity = Mg2+, Al3+ will replace Ti bit after being doped into the crystal lattice to form charge compensation corresponding defect centers to reduce the demand of Sr2+ or Ti3+ vacancy. While Sr-doped Pr will make lattice distortion and transition energy of 4f-5d is very sensitive to crystal electric field changes around Pr atom. Doping different impurities will make electric field distribution around the icon have a different change. It increases energy transfer of 4f-5d transition and improves the luminous intensity of SrTiO3:Pr3+ red phosphor. Dan Guo, Xiaodong Zhang, and Jiangni Yun Copyright © 2014 Dan Guo et al. All rights reserved. Combination of Transverse Mode Selection and Active Longitudinal Mode-Locking of Broad Area Semiconductor Lasers Sun, 13 Jul 2014 00:00:00 +0000 Experimental results of the combination of transverse mode selection and active mode-locking with anti-reflection-coated broad area lasers (BALs) are presented. The BALs are subject to feedback from a free-space external Fourier-optical 4-setup with a reflective spatial frequency filter in the Fourier-plane for transverse mode selection. Driving the BALs with a high frequency modulated pump current above threshold active longitudinal mode-locking is achieved. Pulse durations as low as 88 ps are obtained, while the Gaussian-like fundamental or a higher order transverse mode up to mode number 5 is selected on purpose. Pulse duration and shape are nearly independent of the selected transverse mode. Christoph Doering and Henning Fouckhardt Copyright © 2014 Christoph Doering and Henning Fouckhardt. All rights reserved. Signal Processing Algorithms for Down-Stream Traffic in Next Generation 10 Gbit/s Fixed-Grid Passive Optical Networks Sun, 22 Jun 2014 06:25:42 +0000 We have analyzed the impact of digital and optical signal processing algorithms, that is, Volterra equalization (VE), digital backpropagation (BP), and optical phase conjugation with nonlinearity module (OPC-NM), in next generation 10 Gbit/s (also referred to as XG) DP-QPSK long haul WDM (fixed-grid) passive optical network (PON) without midspan repeaters over 120 km standard single mode fiber (SMF) link for downstream signals. Due to the compensation of optical Kerr effects, the sensitivity penalty is improved by 2 dB by implementing BP algorithm, 1.5 dB by VE algorithm, and 2.69 dB by OPC-NM. Moreover, with the implementation of NL equalization technique, we are able to get the transmission distance of 126.6 km SMF for the 1 : 1024 split ratio at 5 GHz channel spacing in the nonlinear region. Rameez Asif, Rabeea Basir, and Ramshah Ahmad Copyright © 2014 Rameez Asif et al. All rights reserved. Highly Nonlinear and Birefringent Spiral Photonic Crystal Fiber Wed, 11 Jun 2014 12:21:07 +0000 We propose and design a spiral photonic crystal fiber with elliptical air holes for achieving high birefringence, large nonlinearity, and negative dispersion. The structure is designed using chalcogenide glass (As2S3) for different ellipticity ratios of air holes in the cladding and the effect on various properties is observed. The proposed structure has birefringence of the order 10−2, nonlinearity of 26739.42 W−1 m−1, and dispersion of −1136.69 at 0.85 μm. An accurate numerical approach based on finite element method is used for the design and simulation of the structure. Due to high birefringence and negative dispersion, the proposed structure can be used for polarization control and dispersion compensation, respectively. S. Revathi, Srinivasa Rao Inbathini, and Rizwan Ali Saifudeen Copyright © 2014 S. Revathi et al. All rights reserved. The CdS/CdSe/ZnS Photoanode Cosensitized Solar Cells Basedon Pt, CuS, Cu2S, and PbS Counter Electrodes Thu, 27 Feb 2014 11:06:56 +0000 Highly ordered mesoporous TiO2 modified by CdS, CdSe, and ZnS quantum dots (QDs) was fabricated by successive ionic layer adsorption and reaction (SILAR) method. The quantity of material deposition seems to be affected not only by the employed deposition method but also and mainly by the nature of the underlying layer. The CdS, CdSe, and ZnS QDs modification expands the photoresponse range of mesoporous TiO2 from ultraviolet region to visible range, as confirmed by UV-Vis spectrum. Optimized anode electrodes led to solar cells producing high current densities. Pt, CuS, PbS, and Cu2S have been used as electrocatalysts on counter electrodes. The maximum solar conversion efficiency reached in this work was 1.52% and was obtained by using Pt electrocatalyst. CuS, PbS, and Cu2S gave high currents and this was in line with the low charge transfer resistances recorded in their case. Tung Ha Thanh, Dat Huynh Thanh, and Vinh Quang Lam Copyright © 2014 Tung Ha Thanh et al. All rights reserved. Design and Optimization of Polarization Splitting and Rotating Devices in Silicon-on-Insulator Technology Thu, 06 Feb 2014 09:25:09 +0000 We review polarization splitting and rotating photonic devices based on silicon-on-insulator technology platform, focusing on their performance and design criteria. In addition, we present a theoretical investigation and optimization of some rotator and splitter architectures to be employed for polarization diversity circuits. In this context, fabrication tolerances and their influences on device performance are theoretically estimated by rigorous simulations too. Benedetto Troia, Francesco De Leonardis, Mauro Lanzafame, Tommaso Muciaccia, Giuseppe Grasso, Giovanni Giannoccaro, Carlo Edoardo Campanella, and Vittorio M. N. Passaro Copyright © 2014 Benedetto Troia et al. All rights reserved. Burn-In Aging Behavior and Analytical Modeling of Wavelength-Division Multiplexing Semiconductor Lasers: Is the Swift Burn-In Feasible for Long-Term Reliability Assurance? Sun, 08 Dec 2013 09:46:16 +0000 Effective and economical burn-in screening is important for technology development and manufacture of semiconductor lasers. We study the burn-in degradation behavior of wavelength-division multiplexing semiconductor lasers to determine the feasibility of short burn-in. The burn-in is characterized by the sublinear model and correlated with long-term reliability. Jia-Sheng Huang Copyright © 2013 Jia-Sheng Huang. All rights reserved. A Comprehensive Analysis of Plasmonics-Based GaAs MSM-Photodetector for High Bandwidth-Product Responsivity Tue, 24 Sep 2013 11:15:18 +0000 A detailed numerical study of subwavelength nanogratings behavior to enhance the light absorption characteristics in plasmonic-based metal-semiconductor-metal photodetectors (MSM-PDs) is performed by implementation of 2D finite-difference time-domain (FDTD) algorithm. Due to the structure design and changes in the device physical parameters, various devices with different geometries are simulated and compared. Parameters like nano-grating height and duty cycle (DC) are optimized for rectangular and taper subwavelength metal nanogratings on GaAs substrate and their impact on light absorption below the diffraction limits are confirmed. The calculated light enhancement is ~32.7-times for an optimized device in comparison with a conventional MSM-PD. This enhancement is attributed to the plasmonic effects in the near-field region. Narottam Das, Farzaneh Fadakar Masouleh, and Hamid Reza Mashayekhi Copyright © 2013 Narottam Das et al. All rights reserved. Electronically Tunable Wide Band Optical Delay Line Based on InGaAs Quantum Well Microresonators Sun, 08 Sep 2013 08:44:20 +0000 A novel electronically tunable optical delay line based on InGaAs quantum well microresonators is proposed for high frequency RF transmission. The device utilizes the charge-controlled blue shift of the absorption edge in InGaAs quantum wells to change the effective refractive indices of the resonators and couplers, therefore, provides an efficient way to produce variable time delay. A theoretical model based on measurements is used to analyze the device performance. Simulation results for five 3 × 27 μm2 cascaded resonators with bias voltages <0.7 V show a continuous tuning range of 7~68 ps, a ripple delay <1.5 ps, and a useable bandwidth of 39.3 GHz. Yan Zhang and Geoff W. Taylor Copyright © 2013 Yan Zhang and Geoff W. Taylor. All rights reserved. Initial Antinoise Performance Analysis of Pupil Phase Diversity Based on Genetic Algorithm Mon, 02 Sep 2013 11:25:28 +0000 Pupil phase diversity (PPD) wavefront sensor is a new kind of phase-visualization methods, and the output signal of PPD represents the input pupil phase and shows a 1-1 mapping between the position of the wavefront error in the pupil and its position in the output signal. High-precisely wavefront measuring can be obtained under no noise by using appropriate phase restoration algorithm while performance of PPD under noise is unknown. We analyzed antinoise performance of PPD based on genetic algorithm (GA) through measuring the distorted wavefront under different noise level. Simulation results show that wavefront measuring is almost not affected by the existence of noise, which indicates that PPD based on GA can be used in applications with noise. Huizhen Yang and Yaoqiu Li Copyright © 2013 Huizhen Yang and Yaoqiu Li. All rights reserved. Design and Investigation of SST/nc-Si:H/M (M = Ag, Au, Ni) and M/nc-Si:H/M Multifunctional Devices Wed, 07 Aug 2013 13:58:36 +0000 Hydrogenated nanocrystalline Silicon thin films prepared by the very high frequency chemical vapor deposition technique (VHF-CVD) on stainless steel (SST) substrates are used to design Schottky point contact barriers for the purpose of solar energy conversion and passive electronic component applications. In this process, the contact performance between SST and M (M = Ag, Au, and Ni) and between Ag, Au, and Ni electrodes was characterized by means of current-voltage, capacitance-voltage, and light intensity dependence of short circuit () current and open circuit voltage () of the contacts. Particularly, the devices ideality factors, barrier heights were evaluated by the Schottky method and compared to the Cheung's. Best Schottky device performance with lowest ideality factor suitable for electronic applications was observed in the SST/nc-Si:H/Ag structure. This device reflects a of 229 mV with an of 1.6 mA/cm2 under an illumination intensity of ~40 klux. On the other hand, the highest being 9.0 mA/cm2 and the of 53.1 mV were observed for Ni/nc-Si:H/Au structure. As these voltages represent the maximum biasing voltage for some of the designed devices, the SST/nc-Si:H/M and M/nc-Si:H/M can be regarded as multifunctional self-energy that provided electronic devices suitable for active or passive applications. A. F. Qasrawi, Salam M. Kmail, Samah F. Assaf, and Z. M. Saleh Copyright © 2013 A. F. Qasrawi et al. All rights reserved. Multiband Negative Permittivity Metamaterials and Absorbers Sun, 28 Jul 2013 08:19:43 +0000 Design and characteristics of multiband negative permittivity metamaterial and its absorber configuration are presented in this paper. The proposed multiband metamaterial is composed of a novel multibranch resonator which can possess four electric resonance frequencies. It is shown that, by controlling the length of the main branches of such resonator, the resonant frequencies and corresponding absorbing bands of metamaterial absorber can be shifted in a large frequency band. Yiran Tian, Guangjun Wen, and Yongjun Huang Copyright © 2013 Yiran Tian et al. All rights reserved. A Viable Passive Optical Network Design for Ultrahigh Definition TV Distribution Thu, 16 May 2013 12:17:35 +0000 International Telecommunication Union (ITU) has recently standardized ultrahigh definition television (UHD-TV) with a resolution 16 times more than the current high definition TV. An increase in the efficiency of video source coding or in the capacity of transmission channels will be needed to deliver such programs by passive optical network (PON). In this paper, a high capacity integrated PON infrastructure is proposed to overlay ultrahigh definition television by a complete passive coexistence of 10G-PON (XG-PON) and single carrier directly modulated, duo-binary 40G-PON (XLG-PON) signal. The simulation results show error-free transmission performance and further distribution to 32 optical network units (ONUs) on broadcast basis with negligible power penalty over 20 km of bidirectional standard single mode fiber. Shahab Ahmad Niazi, Xiaoguang Zhang, Lixia Xi, Abid Munir, Muhammad Idrees, and Yousaf Khan Copyright © 2013 Shahab Ahmad Niazi et al. All rights reserved. Preparation of Organic Zn-Phthalocyanine-Based Semiconducting Materials and Their Optical and Electrochemical Characterization Thu, 02 May 2013 10:05:06 +0000 In order to increase the species of organic semiconductors, new Zn-phthalocyanines-based organic materials were synthesized and characterized. The new compounds have been characterized by 1H and 13C using NMR, FTIR, and UV-Vis. The absorption, fluorescence, and electrochemical properties were also studied. Green photoluminescence was observed in dilute solutions. In solid thin films, π-π* interactions influenced the optical properties, and redshifted photoluminescence spectra were obtained; red emissions for ZnPAL (647 nm) and ZnPTr (655 nm) were found. By cyclic voltammetry, the electrochemical band gap was estimated to be 1.94 and 1.17 eV for ZnPAl and ZnPTr, respectively. Single-layer diode devices of an indium tin oxide/Zn-phthalocyanine/aluminum configuration were fabricated and showed relatively low turn-on voltages (3.3 V for ZnPAl and 3 V for ZnPTr). Amira Hajri, Sarra Touaiti, and Bassem Jamoussi Copyright © 2013 Amira Hajri et al. All rights reserved. Germanium Doping to Improve Carrier Mobility in CdO Films Wed, 03 Apr 2013 11:32:09 +0000 This investigation addresses the structural, optical, and electrical properties of germanium incorporated cadmium oxide (CdO : Ge) thin films. The focus was on the improvement in carrier mobility to achieve high transparency for near-infrared light and low resistivity at the same time. The properties were studied using X-ray diffraction, SEM, spectral photometry, and Hall measurements. All CdO : Ge films were polycrystalline with high texture orientation along [111] direction. It was observed that it is possible to control the carrier concentration () and mobility () with Ge-incorporation level. The mobility could be improved to a highest value of  cm2/V·s with Ge doping of 0.25 wt% while maintaining the electrical resistivity as low as  Ω·cm and good transparency % in the NIR spectral region. The results of the present work proved to select Ge as dopant to achieve high carrier mobility with low resistivity for application in transparent conducting oxide (TCO) field. Generally, the properties found make CdO : Ge films particularly interesting for the application in optoelectronic devices like thin-film solar cells. A. A. Dakhel Copyright © 2013 A. A. Dakhel. All rights reserved. The Effect of Electron versus Hole Photocurrent on Optoelectric Properties of Wz-GaN Reach-Through Avalanche Photodiodes Mon, 25 Mar 2013 08:56:58 +0000 The authors have made an attempt to investigate the effect of electron versus hole photocurrent on the optoelectric properties of structured Wurtzite-GaN (Wz-GaN) reach-through avalanche photodiodes (RAPDs). The photo responsivity and optical gain of the devices are obtained within the wavelength range of 300 to 450 nm using a novel modeling and simulation technique developed by the authors. Two optical illumination configurations of the device such as Top Mounted (TM) and Flip Chip (FC) are considered for the present study to investigate the optoelectric performance of the device separately due to electron dominated and hole dominated photocurrents, respectively, in the visible-blind ultraviolet (UV) spectrum. The results show that the peak unity gain responsivity and corresponding optical gain of the device are 555.78 mA W−1 and , respectively, due to hole dominated photocurrent (i.e., in FC structure); while those are 480.56 mA W−1 and , respectively, due to electron dominated photocurrent (i.e., in TM structure) at the wavelength of 365 nm and for applied reverse bias of 85 V. Thus, better optoelectric performance of Wz-GaN RAPDs can be achieved when the photocurrent is made hole dominated by allowing the UV light to be shined on the -layer instead of -layer of the device. Moumita Ghosh, Mangolika Mondal, and Aritra Acharyya Copyright © 2013 Moumita Ghosh et al. All rights reserved.