Requirements Study for System Implementation of an Atmospheric Laser Propagation Experiment Program, Volume II

Program planning, ground support and airborne equipment for laser space communication syste

Towards label-free biosensing in compact disk technologies f or point-of-need analysis

Tesis por compendioThis thesis explores new analytical advances using compact disk biosensing technologies, and comprises six scientific publications distributed along four chapters. Special attention is herein payed to Thermochromic Etching Disks (TED) technology (Chapter 1), rational design of disk-based biorecognition assays (Chapter 2), and label-free detection systems for point-of-need analysis (Chapters 3 and 4). First, insights into a novel light-mediated signal developing system for biorecognition assays (based on TED disks and drives) are provided together with an overview of the state-of-the art and future trends in photo- and thermochromic biosensing. This signal developing approach exploits photo- and thermochromism for biosensing in an original manner and represents a potential strategy to simplify signaling processes in bioanalytical systems. Then, how to transform TED technology into lab-on-a-disk systems is addressed. TED has proven to be a very versatile tool to perform sensitive analysis of biorecognition assays, using platforms and scanners easily obtained from regular disks and drives, respectively. Biologically relevant assays of different nature (microarray, cell culture, immunofiltration, turbidimetry, etc.) have been arrayed in a single disk and sensitively analyzed by imaging. Regarding rational design, a theoretical-experimental method (INSEL) based on kinetics and mass-transport modelling for optimizing biorecognition assays and exploring their behavior is presented. INSEL has been implemented as an in silico tool that enables to characterize biointeractions with minimal experimentation, to perform optimizations directed towards custom objectives defined by the user, and to easily compute the effect of critical variables without further experiments. In another study included in this thesis, polycarbonate grooved structures obtained from standard recordable disks (CD-R and DVD-R) were coated with silver and tailored to become SERS-active. This strategy represents a cost-effective and industrially scalable alternative to the SERS substrates typically used for bioanalysis. These disk-based materials have presented tunable plasmonic responses, significant Raman enhancement, and have allowed complex biological targets (such as proteins and exosomes) to be analyzed by SERS without using labeled reagents as tracers. In addition to introduce inexpensive and large-scale SERS substrates for biosensing, this study also suggests the development of prospective Raman scanners based on disk drives. Another approach herein presented addresses the implementation of diffraction-based sensing (DBS) in TED technology in order to conceive disk-based label-free biosensors based on standard disks and drives. At first, a comprehensive experimental assessment of the analytical possibilities offered by DBS is presented. Then, the fabrication of arrays of diffractive protein networks on TED disks is investigated, with which sensitive analysis of antibodies in label-free conditions has been demonstrated, using adapted drives as scanners. This investigation provides important insights into cost-effective and industrially scalable functional materials and detection setups that exploit consumer electronics for label-free biosensing.Esta tesis explora nuevos avances en química analítica usando tecnologías de biosensado basadas en sistemas de disco compacto y comprende seis publicaciones científicas distribuidas a lo largo de cuatro capítulos. Los estudios se han centrado en la tecnología Thermochromic Etching Disks (TED) (Capítulo 1), el diseño racional de ensayos de bioreconocimiento en discos compactos (Capítulo 2), y la detección sin marcaje para realizar análisis in situ (Capítulos 3 y 4). Primero, enmarcado en una discusión del estado del arte y futuras tendencias en biosensado foto y termocrómico, se presenta un nuevo sistema (basado en discos y lectores TED) mediado por luz para el desarrollo de señales en ensayos de bioreconocimiento. Ésta constituye una estrategia novedosa para aprovechar el foto y termocromismo en biosensado, y presenta un gran potencial para simplificar los procesos de desarrollo de señal en sistemas bioanalíticos. A continuación, se aborda cómo transformar la tecnología TED en sistemas analíticos integrados basados en discos compactos. TED ha demostrado ser una herramienta muy versátil para analizar, de forma sensible, ensayos de bioreconocimiento usando plataformas y escáneres fácilmente obtenidos a partir de discos y lectores convencionales, respectivamente. Un único disco ha mostrado poder albergar varios ensayos biológicos importantes y de distinta naturaleza (micromatriz, cultivos celulares, inmunofiltración, turbidimetría, etc.), para ser analizados de forma sensible a través de imágenes En cuanto al diseño racional, se presenta un método teórico-experimental (INSEL), basado en modelos cinéticos y de transporte de masa, para optimizar ensayos de bioreconocimiento y explorar su comportamiento. INSEL se ha implementado como una herramienta in silico que permite caracterizar biointeracciones mediante mínima experimentación, realizar optimizaciones dirigidas a objetivos particulares definidos por el usuario, y computar el efecto de variables críticas de forma sencilla y sin experimentos adicionales. En otro estudio incluido en esta tesis, nanoestructuras en forma de surco obtenidas a partir de discos regrabables convencionales (CD-R y DVD-R) fueron recubiertas con plata y adaptadas para ser activas en SERS. Esta estrategia supone una alternativa, económicamente efectiva e industrialmente escalable, a los sustratos SERS típicamente usados en bioanálisis. Estos materiales han mostrado respuestas plasmónicas sintonizables, una amplificación Raman significativa, y han permitido analizar muestras biológicas complejas (como proteínas y exosomas) mediante SERS sin usar marcadores. Además de introducir sustratos SERS grandes y baratos, este trabajo también sugiere el desarrollo de escáneres Raman basados en lectores de disco. Otra aproximación presentada en esta tesis aborda la implementación de DBS (diffraction-based sensing) en tecnologías TED, con el fin de desarrollar biosensores para detección sin marcaje basados en discos y lectores convencionales. Primero, se presenta una amplia evaluación experimental de las posibilidades analíticas ofrecidas por DBS. A continuación, se investiga la fabricación de multitud de redes difractivas de proteínas sobre discos TED, con las que se ha demostrado la determinación sensible y sin marcaje de anticuerpos, usando lectores adaptados como escáneres analíticos. Esta investigación introduce avances importantes que apuntan al desarrollo de materiales funcionales y sistemas de detección, baratos e industrialmente escalables, que aprovechen las tecnologías de consumo para realizar biosensado sin marcaje.Aquesta tesi explora nous avanços en la química analítica usant tecnologies de biosensat basades en sistemes de disc compacte, i comprèn sis publicacions científiques distribuïdes en quatre capítols. Els estudis s'han centrat en la tecnologia Thermochromic Etching Disks (TED) (Capítol 1), el disseny racional d'assajos de bioreconeixement en discos compactes (Capítol 2), i la detecció sense marcatge per realitzar anàlisi in situ (Capítols 3 i 4). Primer, dins del marc d'una discussió de l'estat de l'art i tendències futures en biosensat foto i termocròmic, es presenta un nou sistema (basat en discos i lectors TED) per al desenvolupament de senyals mitjançant llum, en assajos de bioreconeixement. Aquesta constitueix una nova estratègia per aprofitar el foto i termocromisme en biosensat, mentre que també presenta una gran potencial per simplificar els processos de desenvolupament de senyal en sistemes bioanalítics. Tot seguit, s'aborda com transformar la tecnologia TED en sistemes analítics integrats basats en discos compactes. TED ha demostrat ser una eina molt versàtil per analitzar, de forma sensible, assajos de bioreconeixement usant plataformes i escàners fàcilment obtinguts a partir de discos i lectors convencionals, respectivament. Un únic disc ha mostrat poder albergar diversos assajos biològicament importants i de distinta naturalesa (micromatrius, cultius cel·lulars, immunofiltració, turbidimetria, etc.), per a ser analitzats de forma sensible a través d'imatges. Pel que fa al disseny racional, es presenta un mètode teòric-experimental (INSEL), basat en models cinètics i de transport de massa, per optimitzar assajos de bioreconeixement i explorar el seu comportament. INSEL s'ha implementat com a una eina in silico que permet caracteritzar biointeraccions amb mínima experimentació, realitzar optimitzacions dirigides cap a objectius particulars definits per l'usuari, i computar l'efecte de variables crítiques de forma senzilla i sense experiments addicionals. En un altre estudi inclòs en aquesta tesi, nanoestructures en forma de solc obtingudes a partir de discos compactes regravables convencionals (CD-R i DVD-R) van ser recobertes amb plata i adaptades per a ser actives en SERS. Aquesta estratègia suposa una alternativa, econòmicament efectiva i industrialment escalable, als substrats SERS típicament usats en bioanàlisi. Aquests materials han mostrat respostes plasmòniques sintonitzables, una amplificació Raman significativa, i han permès analitzar mostres biològiques complexes (com proteïnes i exosomes) mitjançant SERS sense usar marcadors. A més d'introduir substrats SERS grans i barats, aquest treball també suggereix el desenvolupament d'escàners Raman basats en lectors de disc. Una altra aproximació presentada en aquesta tesi aborda la implementació de DBS (diffraction-based sensing) en tecnologies TED, per tal de desenvolupar biosensors basats en discos i lectors convencionals que permeten detecció sense marcatge. Primer, es presenta una amplia avaluació experimental de les possibilitats analítiques que ofereix aquesta tècnica. A continuació, s'investiga la fabricació de multitud de xarxes difractives de proteïnes sobre discos TED, amb les quals s'ha demostrat la determinació sensible i sense marcatge d'anticossos, usant lectors adaptats com a escàners analítics. Aquesta investigació introdueix avanços importants que apunten cap al desenvolupament de materials funcionals i sistemes de detecció, barats i industrialment escalables, que aprofiten les tecnologies de consum per dur a terme bioanàlisi sense marcatge.Avellà Oliver, JM. (2017). Towards label-free biosensing in compact disk technologies f or point-of-need analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86128TESISCompendi

Micro- and sub-microstructuring and characterisation of technical surfaces by means of laser direct writing including a novel approach for laser beam profiling

Within recent years, numerous fields of engineering, like mechanics, optics and electronics, have been influenced and revolutionised by the technique of microand nano-structuring. For example, special optical elements for beam shaping, surface structures for the reduction of friction or modern "lab on chip" devices have been produced. Within this thesis a universal system has been developed facilitating the production of such structured surfaces with dimensions down to 500 nm. This system is not only capable of structuring surfaces by means of lithographic processes; it further allows the inspection of surfaces by scanning their topography. To realise such a system, two different technologies have been evaluated: Scanning Near-field Optical Lithography (SNOL), a very sophisticated technique which uses a thin fibre tip to expose a photo resist-covered surface, and confocal scanning technology. Here, the confocal scanning is accomplished using an adapted optical component, the optical pickup unit (OPU), from a gaming console, which turned out to be the most suitable and cost-efficient solution for the realisation of this system. Several test series have been carried out during this work, to verify the performance of the confocal system, both to structure photo resist surfaces and to characterise unknown surfaces. This present work will show the ability of the developed system to produce structures down to the sub-micron range and to characterise unknown surfaces with sub- micron precision. Various patterns have been written into photo resistcoated substrates to structure their surface. Beginning with diffractive optical elements (DOE) for beam shaping, followed by Dammann gratings for twodimensional beam shaping and optical gratings for light guidance as well as producing technical surfaces imitating the properties of sharkskin or simple micromechanical structures, the developed confocal system has shown itself to be flexible and widely-applicable. IV During the development of the confocal system, a strong need for a beam profiling system analysing the light beam diverging from the OPU, was recognised. Due to the fact that no commercially available system was capable of characterising beam sizes within the range of the diffraction limit, a novel method for beam profiling was invented. This method makes use of the fibre tips already applied within the SNOL system, producing tomographical scans of the beam spot

Dynamic Characterisation of the Head-Media Interface in Hard Disk Drives using Novel Sensor Systems

Hard disk drives function perfectly satisfactorily when used in a stable environment, but in certain applications they are subjected to shock and vibration. During the work reported in this thesis it has been found that when typical hard disk drives are subjected lo vibration, data transfer failure is found to be significant at frequencies between 440Hz and 700Hz, at an extreme, failing at only Ig of sinusoidal vibration. These failures can largely be attributed to two key components: the suspension arm and the hard disk. At non-critical frequencies of vibration the typical hard disk drive can reliably transfer data whilst subjected to as much as 45g. When transferring data to the drive controller, the drive's operations are controlled and monitored using BIOS commands. Examining the embedded error signals proved that the drive predominantly failed due lo tracking errors. Novel piezo-electric sensors have been developed to measure unobtrusively suspension arm and disk motion, the results from which show the disk to be the most significant failure mechanism, with its First mode of resonance at around 440Hz. The suspension arm movement has been found to be greatest at IkHz. Extensive modelling of the flexure of the disk, clamped and unclamped, has been undertaken using finite element analysis. The theoretical modelling strongly reinforces the empirical results presented in this thesis. If suspension arm movement is not directly coupled with disk movement then a flying height variation is created. This, together with tracking variations, leads to data transfer corruption. This has been found to occur at IkHz and 2kHz. An optical system has been developed and characterised for a novel and inexpensive flying height measurement system using compact disc player technology

Uncertainty due to speckle noise in laser vibrometry

This thesis presents fundamental research in the field of laser vibrometry for the application to vibration measurements. A key concern for laser vibrometry is the effect of laser speckle which appears when a coherent laser beam scatters from an optically rough surface. The laser vibrometer is sensitive to changes in laser speckle which result from surface motions not in the direction of the incident beam. This adds speckle noise to the vibrometer output which can be indistinguishable from the genuine surface vibrations. This has been termed ‘pseudo-vibration’ and requires careful data interpretation by the vibration engineer. This research has discovered that measurements from smooth surfaces, even when no identifiable speckle pattern is generated, can produce noise and therefore reference to speckle noise, in such circumstances, is inappropriate. This thesis has, therefore, adopted the more general term of pseudo-vibration to include noise generated from any surface roughness or treatment, i.e. including but not limited to speckle noise. This thesis develops and implements novel experimental methods to quantify pseudovibration sensitivities (transverse, tilt and rotation sensitivity) with attention focussed on commercially available laser vibrometers and consideration is given to a range of surface roughnesses and treatments. It investigates, experimentally, the fundamental behaviour of speckles and attempts to formulate, for the first time, a relationship between changes in intensity to pseudo-vibration sensitivity levels. The thesis also develops and implements models for computational simulation of pseudo-vibrations using the fundamental behaviour of speckles. The combination of experimentation and simulation improves current understanding of the pseudo-vibration mechanisms and provides the vibration engineer with a valuable resource to improve data interpretation. Two experimental methods of quantifying pseudo-vibration sensitivity are developed and successfully applied in the evaluation of transverse, tilt and rotation sensitivity for two models of commercial laser vibrometer. These evaluations cover both single beam (translational vibration measurement) and parallel beam (for angular vibration measurement) modes. The first method presented requires correction of the vibrometer measurement with an independent measurement of genuine velocity to produce an iii apparent velocity dominated by the required noise components. The second method requires a differential measurement using two vibrometers to cancel common components such as genuine velocity, leaving only uncorrelated noise from each measurement in the resulting apparent velocity. In each case, a third measurement is required of the surface motion component causing pseudo-vibration and this is used to normalise the apparent velocity. Pseudo-vibration sensitivity is then presented as a map showing the spectral shape of the noise, as a mean and standard deviation of harmonic peaks in the map and as a total rms level across a defined bandwidth. The simulations employ a novel and effective approach to modelling speckle evolution. Transverse and tilt sensitivity are predicted for the first time and are verified by the experimental study. They provide the vibration engineer with the potential to estimate pseudo-vibrations using a simple piece of software. The laser beam spot diameter has a large influence on the pseudo-vibration sensitivity. Transverse sensitivity has been quantified as around 0.03% and 0.01% (per order) of the transverse velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Larger beam spots have been shown to significantly reduce transverse sensitivity and measurements from smoother surfaces have also shown a reduced level of transverse sensitivity. Tilt sensitivity has been quantified at about 0.1 μms-1/degs-1 and 0.3 μms-1/degs-1 (per order) of angular velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Smaller beam spot diameters significantly reduce tilt sensitivity. The surface roughness or treatment has been shown to have little effect on the level of tilt sensitivity. Rotation sensitivity has been quantified at approximately 0.6 μms- 1/rads-1 and 1.9μms-1/rads-1 (per order) of rotation velocity of the rotor for 90 μm and 520 μm. Smaller beam spot diameters have shown a significant reduction in rotation sensitivity and measurements on smoother surfaces have shown a reduced rotation sensitivity. Focussing the laser beam approximately on the rotation axis has also shown a significant reduction in rotation sensitivity. Parallel beam rotation sensitivity has been quantified at 0.016 degs-1/rads-1 and it is demonstrated that this can adequately be estimated using the single beam rotation sensitivity

Magnetic Tunnel Junctions based on spinel ZnxFe3-xO4: Magnetic Tunnel Junctions based onspinel ZnxFe3-xO4

Die vorliegende Arbeit befasst sich mit magnetischen Tunnelkontakten (magnetic tunnel junctions, MTJs) auf Basis des Oxids Zinkferrit (ZnxFe3-xO4). Dabei soll das Potential dieses Materials durch die Demonstration des Tunnelmagnetowiderstandes (tunnel magnetoresistance, TMR) in zinkferritbasierten Tunnelkontakten gezeigt werden. Dazu wurde ein Probendesign für MTJs auf Basis der „pseudo spin valve“-Geometrie entwickelt. Die Basis für dieseStrukturen ist ein Dünnfilmstapel aus MgO (Substrat) / TiN / ZnxFe3-xO4 / MgO / Co. Dieser ist mittels gepulster Laserabscheidung (pulsed laser deposition, PLD) hergestellt. Im Rahmen dieser Arbeit wurden die strukturellen, elektrischen und magnetischen Eigenschaften der Dünnfilme untersucht. Des weiteren wurden die fertig prozessierten MTJ-Bauelemente an einem im Rahmen dieser Arbeit entwickeltem und aufgebautem TMR-Messplatz vermessen. Dabei ist es gelungen einen TMR-Effekt von 0.5% in ZnxFe3-xO4-basierten MTJs nachzuweisen. Das erste Kapitel der Arbeit gibt eine Einführung in die spintronischen Effekte Riesenmagnetowiderstand (giant magnetoresistance, GMR) und Tunnelmagnetowiderstand (TMR). Deren technologische Anwendungen sowie die grundlegenden physikalischen Effekte und Modelle werden diskutiert. Das zweite Kapitel gibt eine Übersicht über die Materialklasse der spinellartigen Ferrite. Der Fokus liegt auf den Materialien Magnetit (Fe3O4) sowie Zinkferrit (ZnxFe3-xO4). Die physikalischen Modelle zur Beschreibung der strukturellen, magnetischen und elektrischen Eigenschaften dieser Materialien werden dargelegt sowie ein Literaturüberblick über experimentelle und theoretische Arbeiten gegeben. Im dritten Kapitel werden die im Rahmen dieser Arbeit verwendeten Probenpräparations- und Charakterisierungsmethoden vorgestellt und technische Details sowie physikalische Grundlagen erläutert. Die Entwicklung eines neuen Probendesigns zum Nachweis des TMR-Effekts in ZnxFe3-xO4-basierten MTJs ist Gegenstand des vierten Kapitels. Die Entwicklung des Probenaufbaus sowie die daraus resultierende Probenprozessierung werden beschrieben. Die beiden letzten Kapitel befassen sich mit der strukturellen, elektrischen und magnetischen Charakterisierung der mittels PLD abgeschiedenen Dünnfilme sowie der Tunnelkontaktstrukturen

DEVELOP NOVEL FRAP TECHNIQUES FOR DETERMINING ANISOTROPIC SOLUTE DIFFUSION IN CARTILAGINOUS TISSUES

Cartilaginous tissue is a connective tissue composed of specialized cells (e.g., chondrocytes and fibroblasts) that produce a large amount of extracellular matrix (ECM), which is comprised mostly of collagen fibers, abundant ground substance rich in proteoglycan, and elastic fibers. It is characterized by its avascular structures within the tissue, implying that nutrition for normal tissue cells, for maintaining a healthy ECM, is mainly supplied through diffusion from nearby vascularized tissues and synovial fluid. Poor nutritional supply to the cartilaginous tissue is believed to be an important factor leading to tissue degeneration. Moreover, due to the complex collagen fiber structures, the solute diffusion properties in cartilaginous tissues are mainly anisotropic (i.e., orientation dependent) in three-dimensional (3D) space. Thus, the determination of nutrient solute anisotropic diffusion properties is crucial for understanding the mechanism of nutrient transport in cartilaginous tissues. Furthermore, characterization of the solute diffusive transport properties in cartilaginous tissues will delineate the relationship between solute diffusion and tissue morphology for further understanding the pathophysiology and etiology of tissue dysfunction and degeneration. Fluorescence recovery after photobleaching (FRAP) is a versatile and widely used tool for the determination of local diffusion properties within solutions, cells, and tissues due to its high spatial resolution offering the possibility to microscopically examine a specific region of a sample. However, there is a lack of FRAP techniques which can determine the two-dimensional (2D) and 3D anisotropic solute diffusion properties in cartilaginous tissues. Therefore, the objective of this project is to develop novel FRAP techniques for determining 2D and 3D anisotropic solute diffusion properties in cartilaginous tissues. First, a new 2D FRAP technique solely based on the spatial Fourier analysis (SFA) was developed to determine the 2D anisotropic diffusion tensor in cartilaginous tissues. The major innovations of this study included the derivation of a close-form solution for the 2D diffusion equation by solely using Fourier transform and the complete determination of three independent components of the 2D diffusion tensor. The new theory was validated by computer simulated FRAP experiments indicating the high accuracy and robustness. The new method was applied to determine the 2D diffusion tensor of 4kDa FITC-Dextran in porcine TMJ discs. It was found that the diffusion of this solute in TMJ discs was inhomogeneous and anisotropic. This study has provided a new method to quantitatively investigate the relationship between transport properties and tissue composition and structure. The obtained transport properties are crucial for future development of numerical models studying nutritional supply within the TMJ disc. Next, the relationship between solute diffusion properties and tissue morphology was investigated by using the new FRAP technique and scanning electron microscopy (SEM). The SEM results demonstrated that the collagen fibers in the TMJ disc aligned anteroposteriorly in the medial, intermediate and lateral regions while aligning mediolaterally in the posterior region. Interestingly, fibers aligned in both the anteroposterior and mediolateral directions were found in the anterior region of the TMJ disc. The diffusion properties were highly correlated with tissue morphology. It was found again that the solute diffusion in the TMJ disc was anisotropic and inhomogeneous, which suggested that tissue structure (i.e., the collagen fiber alignment) and composition (e.g., water content) could be key factors that affect the solute diffusion properties within TMJ discs. Lastly, a new 3D MP-FRAP technique was fully developed for determining 3D anisotropic solute diffusion in cartilaginous tissues. A closed-form solution for the 3D anisotropic diffusion equation was derived by using SFA and all the components of the 3D diffusion tensor were obtained by averaging the diffusivities over a shell of a spherical surface in the frequency domain. The new method was well validated by analyzing computer simulated MP-FRAP data as well as measuring the diffusivities of FICT-Dextran (FD) molecules in the glycerol/PBS solutions. Quantitative analysis of 3D MP-FRAP experiments in the ligament tissues was demonstrated as an in vitro application of our new technique. The results demonstrated that the 3D diffusion properties of two types of FD solutes (FD70 and FD150) in the ligament tissue slices were anisotropic and the diffusion along the fiber orientation was always faster than the other two directions. The advantages of the new 2D and 3D FRAP techniques includes (1) the boundary and initial conditions for these analyses are flexible, so bleaching volume could be any 2D or 3D geometries, (2) the real first recovery image frame or stack right after photobleaching is not required for the diffusion tensor calculation, and (3) the diffusion tensor can be calculated without measuring the point spread function or optical transfer function of the microscope. Due to these features, our techniques can be conveniently carried out on a commercial confocal or multiphoton laser scanning microscope for the 2D or 3D anisotropic diffusion measurements. Future work for this project involves incorporating high-speed fluorescence imaging techniques into our FRAP methods in order to enhance the capabilities and broaden the applications of our method. In addition, investigating diffusion properties in cartilaginous tissues by using other imaging modalities [e.g., magnetic resonance imaging (MRI) and computed tomography (CT)] may lead to translational applications for the FRAP techniques developed in this dissertation

Interferometry for the space mission LISA Pathfinder

Summary available: p. xxvi-xxviii

Linear laser diode arrays for improvement in optical disk recording for space stations

The design and fabrication of individually addressable laser diode arrays for high performance magneto-optic recording systems are presented. Ten diode arrays with 30 mW cW light output, linear light vs. current characteristics and single longitudinal mode spectrum were fabricated using channel substrate planar (CSP) structures. Preliminary results on the inverse CSP structure, whose fabrication is less critically dependent on device parameters than the CSP, are also presented. The impact of systems parameters and requirements, in particular, the effect of feedback on laser design is assessed, and techniques to reduce feedback or minimize its effect on systems performance, including mode-stabilized structures, are evaluated