Advances in Optical Technologies The latest articles from Hindawi © 2018 , Hindawi Limited . All rights reserved. Microfluidic Optical Shutter Flexibly - Actuated via Electrowetting-on-Dielectrics with <20 ms Response Time Sun, 31 Dec 2017 11:34:33 +0000 Tunable microoptics deals with devices of which the optical properties can be changed during operation without mechanically moving solid parts. Often a droplet is actuated instead, and thus tunable microoptics is closely related to microfluidics. One such device/module/cell type is an optical shutter, which is moved in or out of the path of the light. In our case the transmitting part comprises a moving transparent and electrically conductive water droplet, embedded in a nonconductive blackened oil, that is, an opaque emulsion with attenuation of 30 dB at 570 nm wavelength over the 250 μm long light path inside the fluid (15 dB averaged over the visible spectral range). The insertion loss of the cell is 1.5 dB in the “open shutter” state. The actuation is achieved via electrowetting-on-dielectrics (EWOD) with rectangular AC voltage pulses of  V peak-to-peak at 1 kHz. To flexibly allow for horizontal, vertical, and diagonal droplet movement in the upright x-y plane, the contact structures are prepared such that four possible stationary droplet positions exist. The cell is configured as two capacitors in series (along the axis), such that EWOD forces act symmetrically in the front and back of the 60 nl droplet with a response time of <20 ms. Henning Fouckhardt, Johannes Strassner, Carina Heisel, Dominic Palm, and Christoph Doering Copyright © 2017 Henning Fouckhardt et al. All rights reserved. Finite Element Analysis of Thermal Effects in Diode End-Pumped Solid-State Lasers Mon, 10 Apr 2017 07:43:05 +0000 Thermal effects are the main obstacle to getting high power and good beam quality in diode end-pumped solid-state lasers. In this work, a theoretical investigation of thermal effects in single and dual end-pumped solid-state lasers is carried out using finite element analysis (FEA) for a selected number of widely used laser producing materials, namely, Nd:YAG, Yb:YAG, and Nd:KGW. Crystals with different dimensions are also investigated both in single and in dual end-pumped configuration. Finally, the effect of using composite crystals on thermal lensing is investigated. An experiment to measure the thermal focal length for two different crystals was carried out and a comparison with FEA computed focal length of the thermal lens is made. In all cases studied in this work, results show clear effects of thermal lensing with some differences depending on crystal type, pump power, and size. Moustafa Sayem El-Daher Copyright © 2017 Moustafa Sayem El-Daher. All rights reserved. Long-Term Structural Modification of Water under Microwave Irradiation: Low-Frequency Raman Spectroscopic Measurements Tue, 28 Feb 2017 07:24:59 +0000 Raman scattering has been used to study the influence of 2.45 GHz microwave on the structure of water. It has been shown that treatment of the distilled water samples by electromagnetic field leads to long-term changes in the vibrational density of states. It was established that the retention time of structural changes of the water samples depends on the sample volume. The experimental results have been interpreted on the basis of the percolation model. It has been suggested that the change in the chemical composition of the water treated by microwaves can lead to a change in the structure of the percolation cluster formed by the network of hydrogen bonds. The time of the equilibrium structure recovery of the percolation cluster after termination of the microwaves depends on the cluster size and is much slower than the recovery in the chemical composition of water. A. V. Yakunov, M. M. Biliy, and A. P. Naumenko Copyright © 2017 A. V. Yakunov et al. All rights reserved. Comparison of the Optical Amplifiers EDFA and SOA Based on the BER and -Factor in C-Band Mon, 09 Jan 2017 13:46:51 +0000 Currently it is not possible to create a fully optical communication system without a software tool which simulates an optical communication line in real conditions prior to its construction. The aim of this article is to establish a comparison between the EDFA (erbium doped fibre amplifier) and SOA (semiconductor optical amplifier) optical amplifiers in the WDM (wavelength division multiplexing) system. The system contains a four-channel WDM with speed of 10 Gbps and optical fibre with length of 80 km. Simulations are conducted in the programme environment “OptSim.” The quality of the optical communication system is evaluated by the BER (bit error rate) and -factor for individual wavelengths, namely, of 1558 nm and 1562 nm, which are within the C-band. Tomáš Ivaniga and Petr Ivaniga Copyright © 2017 Tomáš Ivaniga and Petr Ivaniga. All rights reserved. Optical Network Technologies for Future Digital Cinema Tue, 13 Dec 2016 07:54:23 +0000 Digital technology has transformed the information flow and support infrastructure for numerous application domains, such as cellular communications. Cinematography, traditionally, a film based medium, has embraced digital technology leading to innovative transformations in its work flow. Digital cinema supports transmission of high resolution content enabled by the latest advancements in optical communications and video compression. In this paper we provide a survey of the optical network technologies for supporting this bandwidth intensive traffic class. We also highlight the significance and benefits of the state of the art in optical technologies that support the digital cinema work flow. Sajid Nazir and Mohammad Kaleem Copyright © 2016 Sajid Nazir and Mohammad Kaleem. All rights reserved. Spherical Aberration of Point Spread Function with Asymmetric Pupil Mask Tue, 29 Nov 2016 13:01:54 +0000 Point spread function underneath spherical wave aberration with antiphase apodization has been obtained by one-dimensional pupil mask functions. In the presence of spherical aberration, suppression of optical side-lobes has increased on one side of the point spread function with the width of the periphery strips within the pupil mask. On introducing wave aberration effect, there exists dependence of the lateral resolution of central peak of the asymmetric point spread function on the amount of amplitude masking. However, the magnitude of intensity of central peak is originated be to amplified by the highest degree of amplitude and phase masking. Additionally, for aberrated asymmetric PSF, FWHM increases and it further decreases with the control parameters of amplitude and phase mask. The magnitude of this corollary can quantify the super resolution of diffracted structures under spherical aberration. Naresh Kumar Reddy Andra and Karuna Sagar Dasari Copyright © 2016 Naresh Kumar Reddy Andra and Karuna Sagar Dasari. All rights reserved. A Polymer Film Dye Laser with Spatially Modulated Emission Controlled by Transversely Distributed Pumping Tue, 27 Sep 2016 07:35:04 +0000 Spatial modulation of laser emission controlled by the structure of excitation light field was demonstrated. A dye doped polymer film as an active medium was sandwiched between two laser mirrors forming a laser cell. The pumping was performed by an interference pattern formed with two mutually coherent beams of the second harmonic of a Q-switched Nd:YAG laser (532 nm) and located in the plane of the laser cell. The laser emission was observed normally on the plane of the cell. The cross section of the obtained laser emission was modulated in intensity with an interval between maximums depending on the period of the pumping interference pattern. Thus, the emitted light field qualitatively looks like diffraction from an elementary dynamic hologram, that is, a holographic diffraction grating. Zurab V. Wardosanidze, Andro Chanishvili, and Guram Chilaya Copyright © 2016 Zurab V. Wardosanidze et al. All rights reserved. Modeling Nonlinear Acoustooptic Coupling in Fiber Optics Based on Refractive Index Variation due to Local Bending Sun, 18 Sep 2016 09:04:00 +0000 A detailed procedure is presented to compute analytically the acoustooptic coupling coefficient between copropagating core and lowest-order cladding modes in tapered fiber optics. Based on the effect of the local bending, the linear and nonlinear variations in the refractive index are modeled. A set of equations and parameters are presented in order to calculate the influence of acoustooptic effect in nonlinear pulse propagation. We will show that as the tapered fiber diameter decreases more energy can be transferred to the cladding and the nonlinear phenomena can compensate the coupling coefficients effects. Catalina Hurtado Castano, Rodrigo Acuna Herrera, and Pedro I. Torres Copyright © 2016 Catalina Hurtado Castano et al. All rights reserved. Infrared Radiation Assisted Stokes’ Law Based Synthesis and Optical Characterization of ZnS Nanoparticles Sun, 21 Feb 2016 14:16:01 +0000 The strategy and technique exploited in the synthesis of nanostructure materials have an explicit effect on the nucleation, growth, and properties of product materials. Nanoparticles of zinc sulfide (ZnS) have been synthesized by new infrared radiation (IR) assisted and Stokes’ law based controlled bottom-up approach without using any capping agent and stirring. IR has been used for heating the reaction surface designed in accordance with the well-known Stokes law for a free body falling in a quiescent fluid for the synthesis of ZnS nanoparticles. The desired concentration of aqueous solutions of zinc nitrate (Zn(NO3)2·4H2O) and thioacetamide (CH3CSNH2) was reacted in a controlled manner by IR radiation heating at the reaction area (top layer of reactants solution) of the solution which results in the formation of ZnS nanoparticles at ambient conditions following Stokes’ law for a free body falling in a quiescent fluid. The phase, crystal structure, and particle size of as-synthesized nanoparticles were studied by X-ray diffraction (XRD). The optical properties of as-synthesized ZnS nanoparticles were studied by means of optical absorption spectroscopic measurements. The optical energy band gap and the nature of transition have been studied using the well-known Tauc relation with the help of absorption spectra of as-synthesized ZnS nanoparticles. Beer Pal Singh, Ravish Kumar Upadhyay, Rakesh Kumar, Kamna Yadav, and Hector I. Areizaga-Martinez Copyright © 2016 Beer Pal Singh et al. All rights reserved. Novel Raman Parametric Hybrid L-Band Amplifier with Four-Wave Mixing Suppressed Pump for Terabits Dense Wavelength Division Multiplexed Systems Mon, 15 Feb 2016 09:55:21 +0000 We demonstrate improved performance of parametric amplifier cascaded with Raman amplifier for gain of 54.79 dB. We report amplification of L-band using 100 × 10 Gbps Dense Wavelength Division Multiplexed (DWDM) system with 25 GHz channel spacing. The gain achieved is the highest reported so far with gain flatness of 3.38 dB without using any gain flattening technique. Hybrid modulated parametric pump is used for suppressing four-wave mixing (FWM) around pump region, resulting in improvement of gain flatness by 2.42 dB. The peak to peak variation of gain is achieved less than 1.6 dB. DWDM system with 16-channel, 25 GHz spaced system has been analyzed thoroughly with hybrid modulated parametric pump amplified Raman-FOPA amplifier for gain flatness and improved performance in terms of BER and -factor. Gaganpreet Kaur, Sanjay Sharma, and Gurmeet Kaur Copyright © 2016 Gaganpreet Kaur et al. All rights reserved. Encryption of 3D Point Cloud Object with Deformed Fringe Mon, 15 Feb 2016 06:27:54 +0000 A 3D point cloud object encryption method was proposed with this study. With the method, a mapping relationship between 3D coordinates was formulated and coordinate was transformed to deformed fringe by a phase coding method. The deformed fringe and gray image were used for encryption and decryption with simulated off-axis digital Fresnel hologram. Results indicated that the proposed method is able to accurately decrypt the coordinates and gray image of the 3D object. The method is also robust against occlusion attacks. Xin Yang and Hongbo Zhang Copyright © 2016 Xin Yang and Hongbo Zhang. All rights reserved. Performance Trade-Offs for Wavelength Striping Optical Switching Using a Novel Star Architecture Thu, 11 Feb 2016 07:42:21 +0000 This work describes various performance trade-offs that arise from the use of a technique for optical switching under various network topologies. Such switching operation can be summarized as follows: (a) user data are divided into fixed-length fragments, (b) each fragment is assigned to a different wavelength, and (c) all wavelengths are simultaneously switched to the egress links. This concept of dividing user data into several wavelengths to be simultaneously switched is called wavelength striping and its purpose is to reduce latency and increase throughput for short distance interconnects. We depart from previous work where a building block implementing this basic switching function has been built around semiconductor optical amplifiers (SOAs). In this paper, we investigate diverse trade-offs that arise from the use of this switching approach in different network topologies. One of the main issues addressed in this paper is the relation between cascadability and bit error rate (BER). In this case, our results indicate that a switch fabric can cascade up to five stages without exceeding a BER of 10−9 and without incurring in power budget problems. We also show that the performance degradation, introduced by cascading SOAs, can be compensated with a star interconnect architecture that is introduced. Other issues addressed in this paper are the effect of scalability on cost and the effect of latency on TCP performance and reliability. Enrique Rodriguez-Colina, Michael Pascoe-Chalke, and Miguel Lopez-Guerrero Copyright © 2016 Enrique Rodriguez-Colina et al. All rights reserved. Performance Investigation of 40 GB/s DWDM over Free Space Optical Communication System Using RZ Modulation Format Wed, 10 Feb 2016 06:54:17 +0000 We successfully demonstrate 40 GB/s 8 channels’ Dense Wavelength Division Multiplexing (DWDM) over free space optical (FSO) communication system. Each channel is transmitting 5 GB/s data rate in downstream separated by 0.8 nm (100 GHz) channel spacing with 1.8 GHz filter bandwidth. DWDM over FSO communication system is very effective in providing high data rate transmission with very low bit error rate (BER). The maximum reach of designed system is 4000 m without any compensation scheme. The simulation work reports minimum BER for Return-to-Zero (RZ) modulation format at different channels 1, 4, and 8 are found to be , , and at 4000 m distance, respectively. Sharp increase in BER occurs if data rate and distance increase up to 10 GB/s and 5000 m. Sooraj Parkash, Anurag Sharma, Harsukhpreet Singh, and Harjit Pal Singh Copyright © 2016 Sooraj Parkash et al. All rights reserved. Theoretical Description of the Glass Preparation with the Necessary Optical Properties Thu, 04 Feb 2016 09:10:06 +0000 The method to get the glass media with necessary optical characteristics is proposed. This method is based on inserting a necessary number of heterogeneous centers of given activity into the system. The theoretical description of the nucleation process in such situation is given and the resulting formulas allow choosing the characteristics of heterogeneous centers necessary to get the required optical characteristics of the media. Victor Kurasov Copyright © 2016 Victor Kurasov. All rights reserved. Quartz Enhanced Photoacoustic Spectroscopy for Detection of Improvised Explosive Devices and Precursors Mon, 01 Feb 2016 14:01:43 +0000 A compact portable and standalone point sensor has been developed for the detection and identification of precursors of improvised explosive devices (IEDs) and to be part of a network of sensors for the discovery of hidden bomb factories in homeland security applications. The sensor is based on quartz enhanced photoacoustic spectroscopy (QEPAS), and it implements a broadly tunable external cavity quantum cascade laser source (EC-QCL). It makes use of an optical cell purposely designed with a miniaturized internal volume, to achieve fast response and high sensitivity, and that can also be heated to improve sensitivity towards less volatile compounds. The sensor has been assembled and successfully tested in the lab with several compounds, including IED’s precursors such as acetone, nitromethane, nitric acid, and hydrogen peroxide. The identification capability and limits of detection near the ppm level have been estimated for all these compounds. Roberto Viola, Nicola Liberatore, Domenico Luciani, and Sandro Mengali Copyright © 2016 Roberto Viola et al. All rights reserved. A Comparison of Different A-, A-B-, and B-Site Incorporated in (Ba0.5Sr0.5)TiO3 on Photocatalytic Application Mon, 28 Dec 2015 08:50:36 +0000 The structural modification of Ba0.5Sr0.5TiO3 (BST) nanocatalyst was successfully synthesized via sol-gel process. The BST catalyst was modified by A-site (A-BST), A-B-site (A-B-BST), and B-site (B-BST) in order to investigate the effect of structurally modified BST catalyst for photocatalytic decolorization of methylene blue. The structurally modified BST catalysts can increase the nonradiation energy such as phonon energy compared to that of BST one. The partial incorporation of the A-BST catalyst was evidenced by the higher-ordered structure by increasing number of Ti4+ ions and the lattice oxygen. The A-B-BST and A-BST catalysts were given more electron-transfer in the TiO6 than that of BST and B-BST catalysts, respectively. The A-B-BST catalyst promoted the oxidation of the lattice oxygen by holes capturing to form the chemisorbed oxygen, presenting the highest photobleaching activity of methylene blue. On the other hand, more oxygen vacancies recombination of BST catalyst compared to that of structurally modified BST catalysts presented the reduction of photocatalytic activity. Tassanee Tubchareon, Rachan Klaysri, and Piyasan Praserthdam Copyright © 2015 Tassanee Tubchareon et al. All rights reserved. Growth and Characterization of Benzimidazolium Salicylate: NLO Property from a Centrosymmetric Crystal Thu, 29 Oct 2015 06:38:44 +0000 A new organic charge transfer molecular complex salt of benzimidazolium salicylate (BSL) single crystals was grown by the slow evaporation solution growth technique using methanol as a solvent at room temperature. The grown crystals were characterised by single crystal X-ray diffraction (XRD) which confirms that the crystal belongs to monoclinic system with the centrosymmetric space group P21/. The crystalline perfection of the grown crystal was analyzed by high resolution X-ray diffraction (HRXRD). The presence of various functional groups was identified by FTIR spectrum. UV-Vis spectral study reveals that the BSL crystal is optically transparent in the wavelength region 342 nm–1100 nm. Dielectric measurements of the crystal at various frequencies were also determined. The mechanical properties of the grown crystal were assessed using Vickers microhardness testing. Nonlinear optical property of the crystal was confirmed using Kurtz and Perry powder technique and the SHG efficiency of the BSL crystal is 0.7 times greater than that of the standard KDP crystal. M. Amudha, R. Rajkumar, V. Thayanithi, and P. Praveen Kumar Copyright © 2015 M. Amudha et al. All rights reserved. Enabling 4-Lane Based 400 G Client-Side Transmission Links with MultiCAP Modulation Tue, 11 Aug 2015 06:49:59 +0000 We propose a uniform solution for a future client-side 400 G Ethernet standard based on MultiCAP advanced modulation format, intensity modulation, and direct detection. It employs 4 local area networks-wavelength division multiplexing (LAN-WDM) lanes in 1300 nm wavelength band and parallel optics links based on vertical cavity surface emitting lasers (VCSELs) in 850 nm wavelength band. Total bit rate of 432 Gbps is transmitted over unamplified 20 km standard single mode fiber link and over 40 km link with semiconductor optical amplifier. 70.4 Gb/s transmission over 100 m of OM3 multimode fiber using off-the-shelf 850 nm VCSEL with 10.1 GHz 3 dB bandwidth is demonstrated indicating the feasibility of achieving 100 Gb/s per lane with a single 25 GHz VCSEL. In this review paper we introduce and present in one place the benefits of MultiCAP as versatile scheme for use in a number of client-side scenarios: short range, long range, and extended range. Anna Tatarczak, Miguel Iglesias Olmedo, Tianjian Zuo, Jose Estaran, Jesper Bevensee Jensen, Xiaogeng Xu, and Idelfonso Tafur Monroy Copyright © 2015 Anna Tatarczak et al. All rights reserved. Optical Spatial Filter to Suppress Beam Wander and Spatial Noise Induced by Atmospheric Turbulence in Free-Space Optical Communications Mon, 18 May 2015 06:18:25 +0000 We propose an optical spatial filter (OSF) method to suppress beam wander and spatial noise effects. Signal from random displacements of the focus spot around the optical axis within the constricted area is collected. This method advantageously suppresses fluctuations in signal intensity. The OSF consists of a pinhole and cone reflector. The pinhole produces Fresnel diffraction on the focus spot. The cone reflector provides directed reflectance onto the pinhole for random focus spot displacements due to beam wander. The calculations of signal power are based on fluctuations of signal intensity that are minimized by the circular aperture function of the pinhole and the cosine of the reflectance angle from the cone reflector. The method is applied to free-space optical communications at a wavelength of 1.55 μm with an atmospheric chamber to provide optical propagation media. Based on calculations, the beam wander angles that can be received by the OSF are from 14.0° to 28.0°. Moreover, based on experiment, the OSF with a pinhole diameter of 20.0 μm and cone reflector diameter of 1.5 mm produces signal power of −15.3 dBm. Both calculations and experiment show that the OSF enhances the received signal power in the presence of turbulence. Ucuk Darusalam, Purnomo Sidi Priambodo, and Eko Tjipto Rahardjo Copyright © 2015 Ucuk Darusalam et al. All rights reserved. Robust Discrimination between Single Gold Nanoparticles and Their Dimers in Aqueous Solution for Ultrasensitive Homogeneous Bioassays Tue, 07 Apr 2015 12:21:47 +0000 We propose a robust method to distinguish isolated single gold nanoparticles (AuNP monomers) and their dimers under Brownian motion, a key for ultrasensitive homogeneous bioassays, including AuNP sandwich assays. To detect dimers and distinguish them from a larger number of monomers in aqueous solution, single-particle polarization microscopy was performed. For the accurate detection of individual particles, the optical anisotropy and rotational diffusion time are measured because a dimer is much more anisotropic than the nearly spherical monomer and the rotational diffusion time of a dimer is four times that of a monomer. By employing an autocorrelation analysis, we defined a measure of distinguishing that simultaneously enables high detection probability and low error probability. The detection platform offers homogeneous DNA hybridization assays and immunoassays at the subpicomolar level. Jun Kobayashi, Yukari Takeshita, Naoto Mizuno, Keio Esashika, and Toshiharu Saiki Copyright © 2015 Jun Kobayashi et al. All rights reserved. Nanophotonics: Fabrications and Application of Nanoscale Optics to Novel Photonic Devices Tue, 03 Feb 2015 07:30:50 +0000 Takashi Yatsui, Chennupati Jagadish, and Gilles Lerondel Copyright © 2015 Takashi Yatsui et al. All rights reserved. Switching the Localized Surface Plasmon Resonance of Single Gold Nanorods with a Phase-Change Material and the Implementation of a Cellular Automata Algorithm Using a Plasmon Particle Array Mon, 02 Feb 2015 10:39:11 +0000 We investigate the modulation of the localized surface plasmon resonance (LSPR) of a gold nanorod (AuNR) using a GeSbTe film as an active medium. We demonstrate high-contrast switching of LSPR in an AuNR/GST/Au thin film sandwich structure upon phase change. To go beyond this single-particle switching functionality, we consider a plasmon particle system interacting with a phase-change material (PCM) to discuss the possibility of parallel processing devices with memory functionality, exploiting the plasticity and threshold behavior that are inherent characteristics of PCMs. We demonstrate that the temporal and spatial evolution of a plasmon-PCM array system can be equivalent to a cellular automata algorithm. Takashi Hira, Takayuki Uchiyama, Kenta Kuwamura, Yuya Kihara, Tasuku Yawatari, and Toshiharu Saiki Copyright © 2015 Takashi Hira et al. All rights reserved. GaP Homojunction LEDs Fabricated by Dressed-Photon-Phonon-Assisted Annealing Mon, 02 Feb 2015 08:35:03 +0000 By using a homojunction-structured GaP single crystal, we generated a photon energy higher than the bandgap energy (2.26 eV). The device was fabricated by performing dressed-photon-phonon- (DPP-) assisted annealing, while applying a forward-bias current, on a p-n homojunction structure formed by implanting a dopant (Zn) into an n-type GaP substrate. The DPP-assisted annealing increased the light emission intensity in an energy band above 2.32 eV by at least 550% compared with that before annealing. Jun Hyoung Kim, Tadashi Kawazoe, and Motoichi Ohtsu Copyright © 2015 Jun Hyoung Kim et al. All rights reserved. Realization of Ultraflat Plastic Film Using Dressed-Photon-Phonon-Assisted Selective Etching of Nanoscale Structures Mon, 02 Feb 2015 08:24:00 +0000 We compared dressed-photon-phonon (DPP) etching to conventional photochemical etching and, using a numerical analysis of topographic images of the resultant etched polymethyl methacrylate (PMMA) substrate, we determined that the DPP etching resulted in the selective etching of smaller scale structures in comparison with the conventional photochemical etching. We investigated the wavelength dependence of the PMMA substrate etching using an O2 gas. As the dissociation energy of O2 is 5.12 eV, we applied a continuous-wave (CW) He-Cd laser ( nm, 3.81 eV) for the DPP etching and a 5th-harmonic Nd:YAG laser ( nm, 5.82 eV) for the conventional photochemical etching. From the obtained atomic force microscope images, we confirmed a reduction in surface roughness, , in both cases. However, based on calculations involving the standard deviation of the height difference function, we confirmed that the conventional photochemical etching method etched the larger scale structures only, while the DPP etching process selectively etched the smaller scale features. Takashi Yatsui, Wataru Nomura, and Motoichi Ohtsu Copyright © 2015 Takashi Yatsui et al. All rights reserved. Mass Screening of Vision in the Cinemas and a Maculascope for the Masses: Revival of Haidinger’s Brush Wed, 31 Dec 2014 10:37:50 +0000 Haidinger’s brush, an entoptic phenomenon, is very useful in checking central vision loss and eccentric fixation. Haidinger’s brush is also used to provide vision training for subjects affected by eccentric fixation/lazy eye. We propose the use of Haidinger’s brush for mass self-screening of vision in cinema theatres in one go and at no cost to the subjects. We also suggest a simple projection technology for mass vision screening of subjects in waiting rooms or at shop windows of eye-care practitioners. Finally, we propose a new affordable handheld device for vision training. The test and the devices that we propose would increase public awareness of eye health, improve vision in children, and help prevent blindness in the elderly. Kodikullam V. Avudainayagam and Chitralekha S. Avudainayagam Copyright © 2014 Kodikullam V. Avudainayagam and Chitralekha S. Avudainayagam. All rights reserved. Performance of All-Optical XNOR Gate Based on Two-Photon Absorption in Semiconductor Optical Amplifiers Wed, 31 Dec 2014 08:45:03 +0000 All-optical logic XNOR gate is realized by a series combination of XOR and INVERT gates. This Boolean function is realized by using Mach-Zehnder interferometers (MZIs) and exploiting the nonlinear effect of two-photon absorption (TPA) in semiconductor optical amplifiers (SOAs). The employed model takes into account the impact of amplified spontaneous emission (ASE), input pulse energy, pulsewidth, SOAs carrier lifetime, and linewidth enhancement factor (α-factor) on the gate’s output quality factor (Q-factor). The outcome of this study shows that the all-optical XNOR gate is indeed feasible with the proposed scheme at 250 Gb/s with both logical correctness and acceptable quality. Amer Kotb Copyright © 2014 Amer Kotb. All rights reserved. Optical Biosensor Based on Microbendings Technique: An Optimized Mean to Measure the Bone Strength Wed, 24 Dec 2014 13:52:06 +0000 Osteoporosis, a disease in humans, reduces bone mineral density. The microarchitecture of the bone gets deteriorated with change in variety of proteins in the bone. Therefore, a quantitative assessment of the strength of human bone, considering its structural properties and degradation due to aging, disease, and therapeutic treatment, becomes an integral part of the bioengineering studies. This paper presents a model of fiber optic biosensors (FOBs) which utilizes microbending technique to measure the strength of the bone. In parallel, an artificial neural network (ANN) based test bench has been developed for the optimization of FOBs strain measurement in orthoapplications using MATLAB. The performance accuracy of the given model appears to be considerable in ensuring the detection of the onset of osteoporosis. Preeti Singh and Abhishek Shrivastava Copyright © 2014 Preeti Singh and Abhishek Shrivastava. All rights reserved. Comparative Study of Fiber Bragg Gratings and Fiber Polarimetric Sensors for Structural Health Monitoring of Carbon Composites Tue, 18 Nov 2014 11:37:37 +0000 A comparative study is presented between Bragg grating (FBG) and polarimetric sensors (PS), two of the most promising fiber optic sensing techniques for the structural health monitoring of smart materials based on carbon fiber composites. The paper describes the realization of a test plate equipped with both types of sensors and reports the characterization under static and dynamic conditions, highlighting pros and cons of both technologies. The FBG setup achieves 1.15 ± 0.0016 pm/kg static load response and reproduces dynamic excitation with 0.1% frequency uncertainty; the PS system exhibits a sensitivity of 1.74 ± 0.001 mV/kg and reproduces dynamic excitation with 0.5% frequency uncertainty. It is shown that the PS technology is a good and cheap alternative to FBG for vibration-monitoring of small structures at high frequency. Massimo Olivero, Guido Perrone, Alberto Vallan, and Daniele Tosi Copyright © 2014 Massimo Olivero et al. All rights reserved. Implementation of a Phase Only Spatial Light Modulator as an Atmospheric Turbulence Simulator at 1550 nm Wed, 06 Aug 2014 07:50:27 +0000 Modeling and simulating atmospheric turbulence in a controlled environment have been a focus of interest for scientists for decades. The development of new technologies allows scientists to perform this task in a more realistic and controlled environment and provides powerful tools for the study and better understanding of the propagation of light through a nonstatic medium such as the atmosphere. Free space laser communications (FSLC) and studies in light propagation through the atmosphere are areas which constantly benefit from breakthroughs in technology and in the development of realistic atmospheric turbulence simulators, in particular (Santiago et al. 2011). In this paper, we present the results from the implementation of a phase only spatial light modulator (SLM) as an atmospheric turbulence simulator for light propagation in the short-wave infrared (SWIR) regime. Specifically, we demonstrate its efficacy for its use in an FSLC system, at a wavelength of 1550 nm. Carlos Font, Freddie Santiago, G. Charmaine Gilbreath, David Bonanno, Blerta Bajramaj, Christopher Wilcox, Sergio Restaino, and Scott Mathews Copyright © 2014 Carlos Font et al. All rights reserved. Emission Spectral Control of a Silicon Light Emitting Diode Fabricated by Dressed-Photon-Phonon Assisted Annealing Using a Short Pulse Pair Sun, 06 Jul 2014 10:44:24 +0000 We fabricated a high-efficiency infrared light emitting diode (LED) via dressed-photon-phonon (DPP) assisted annealing of a p-n homojunctioned bulk Si crystal. The center wavelength in the electroluminescence (EL) spectrum of this LED was determined by the wavelength of a CW laser used in the DPP-assisted annealing. We have proposed a novel method of controlling the EL spectral shape by additionally using a pulsed light source in order to control the number of phonons for the DPP-assisted annealing. In this method, the Si crystal is irradiated with a pair of pulses having an arrival time difference between them. The number of coherent phonons created is increased (reduced) by tuning (detuning) this time difference. A Si-LED was subjected to DPP-assisted annealing using a 1.3 μm ( eV) CW laser and a mode-locked pulsed laser with a pulse width of 17 fs. When the number of phonons was increased, the EL emission spectrum broadened toward the high-energy side by 200 meV or more. The broadening towards the low-energy side was reduced to 120 meV. Tadashi Kawazoe, Naoki Wada, and Motoichi Ohtsu Copyright © 2014 Tadashi Kawazoe et al. All rights reserved.