In this thesis a new and powerful approach for modeling laser cavity eigenmodes is presented. This approach is based on an eigenvalue problem for singularly perturbed partial differential operators with complex coefficients; such operators have not been investigated in detail until now. The eigenvalue problem is discretized by finite elements, and convergence of the approximate solution is proved by using an abstract convergence theory also developed in this dissertation. This theory for the convergence of an approximate solution of a (quadratic) eigenvalue problem, which particularly can be applied to a finite element discretization, is interesting on its own, since the ideas can conceivably be used to handle equations with a more complex nonlinearity. The discretized eigenvalue problem essentially is solved by preconditioned GMRES, where the preconditioner is constructed according to the underlying physics of the problem. The power and correctness of the new approach for computing laser cavity eigenmodes is clearly demonstrated by successfully simulating a variety of different cavity configurations. The thesis is organized as follows: Chapter 1 contains a short overview on solving the so-called Helmholtz equation with the help of finite elements. The main part of Chapter 2 is dedicated to the analysis of a one-dimensional model problem containing the main idea of a new model for laser cavity eigenmodes which is derived in detail in Chapter 3. Chapter 4 comprises a convergence theory for the approximate solution of quadratic eigenvalue problems. In Chapter 5, a stabilized finite element discretization of the new model is described and its convergence is proved by applying the theory of Chapter 4. Chapter 6 contains computational aspects of solving the resulting system of equations and, finally, Chapter 7 presents numerical results for various configurations, demonstrating the practical relevance of our new approach. / In dieser Arbeit wird ein neues und mächtiges Verfahren für die Modellierung von Eigenmoden in Laser-Resonatoren vorgestellt. Dieses Verfahren basiert auf einem Eigenwertproblem für singulär gestörte Differentialoperatoren mit komplexen Koeffizienten; solche Operatoren sind bisher noch nicht detailliert untersucht worden. Das Eigenwertproblem wird mit Finiten Elementen diskretisiert, und die Konvergenz der Finite-Elemente-Lösung wird bewiesen durch Anwendung einer abstrakten Konvergenztheorie, die ebenfalls in dieser Dissertation entwickelt wird. Diese Theorie für die Konvergenz einer Näherungslösung eines (quadratischen) Eigenwertproblems ist für sich allein interessant, da die Beweisideen auch auf Fälle mit einer komplizierteren Nichtlinerität angewendet werden können. Das diskretisierte Eigenwertproblem wird im Wesentlichen mit einem vorkonditionierten GMRES-Verfahren gelöst, wobei der Vorkonditionierer unter Beachtung der dem Problem zugrunde liegenden Physik konstruiert wurde. Die Mächtigkeit und Korrektheit unseres neuen Verfahrens zur Bestimmung von Eigenmoden in Laser-Resonatoren wird klar gezeigt dadurch, dass eine Vielzahl verschiedener Konfigurationen damit erfolgreich gerechnet werden können. Die Dissertation ist wie folgt aufgebaut: Kapitel 1 enthält eine kurzen Überblick über das Lösen der sogenannten Helmholtz-Gleichung mit Hilfe von Finiten Elementen. Der Großteil des Kapitels 2 beschäftigt sich mit der Analyse eines eindimensionalen Modellproblems. Dieses Modellproblem enthält die Hauptidee des neuen Modells für Eigenmoden eines Laser-Resonators, welches in Kapitel 3 entwickelt wird. Kapitel 4 beinhaltet eine Konvergenztheorie für Näherungslösungen von quadratischen Eigenwertproblemen. In Kapitel 5 wird eine stabilisierte Finite-Elemente-Diskretisierung des neuen Modells beschrieben, und dessen Konvergenz mit Hilfe der Theorie aus Kapitel 4 bewiesen. Kapitel 6 beschäftigt sich damit, welche Verfahren aus der numerischen linearen Algebra verwendet werden, um das diskrete Problem zu lösen. Schließlich finden sich zum Nachweis der praktischen Relavanz des Verfahrens in Kapitel 7 numerische Ergebnisse für eine Vielzahl von Konfigurationen.

A dissertation submitted to the Faculty Of Science in partial fulfilment of the requirements for the degree of Master of Science by research only in the School of Physics, University of the Witwatersrand, Johannesburg. July 11, 2017. / A discrete Q-switched laser that gives a side-lobed single pulse as a laser output was implemented; followed by studying energy extraction e ciencies and pulse characterisation. The aim was to help design a passively Q-switched laser that gives a smooth single pulse of optimum energy as a laser output. The smoothness feature in a single pulse is important in some applications such as range nding. The concepts are demonstrated both experimentally and numerically; the latter using Fox-Li approach to modeling resonator modes with the Fresnel's integral for the system under study. In the rst two chapters, fundamentals of how a laser works and the spatial mode development are studied. In chapter 1, the principles of a laser are discussed: absorption, spontaneous and stimulated emission. Also, di erent types of pumping sources and resonator con gurations that can be used are discussed. In chapter 2, the focus is on developing spatial modes of a laser. The fundamental and high order modes are discussed together with their propagation laws. Then a numerical method is used to nd the eigenmodes of an arbitrary resonator con guration. This numerical method is used to simulate propagation of a fundamental mode and the simulation results are compared to analytical propagation laws. Then, this numerical method is used to simulate a laser resonator. The eigenmode of the lowest loss in the resonator was found. In chapters 3 and 4, experimental work is done on a Q-switched laser where the focus is on the overall laser performance. In chapter 3, Q-switched laser output energies are studied for di erent combinations of Q-switch transmission values and output coupler re ectivities. In addition, the in uence of spatial modes on a Q-switched pulse shape and pulse width are studied, taking into account beam divergence. In chapter 4, conclusions and future work are presented. In future work, the knowledge of spatial mode in uence on pulse shape, pulse width and beam divergence from chapter 3 is exploited. Then particular resonator con guration that gives optimised output results (Q-switched laser output energy, beam divergence, pulse shape and pulse width) is chosen. On that particular resonator, di erent Q-switch transmission values are studied, but now looking only at beam divergence and pulse width. Also, some suggestions on further improving laser performance are given. / LG2018

Dans un premier temps, nous avons optimisé des structures laser VECSEL dans le but de maximiser la puissance émise par une gestion thermique adéquate. Les structures conçues et fabriquées contiennent une zone active à base d’InP pour l’émission à 1.55 µm. Un miroir hybride métal- semiconducteur à base d’un miroir de Bragg GaAs/AlAs est intégré à la zone active. La structure semiconductrice est intégrée avec différents substrats hôtes de bonne conductivité thermique sur la base de simulations numériques, et les performances des dispositifs fabriqués sont évaluées expérimentalement sous pompage optique Les VECSELs intégrés sur substrat diamant CVD présentent les puissances de sortie les plus élevées, et sont de bons candidats pour l’émission de puissance (> 500 mW) à 1.55 µm et pour les expériences de blocage de modes. D’un autre côté nous montrons que l’intégration d’un substrat de cuivre par voie électrochimique représente une approche flexible et faible-coût, pour atteindre une puissance de sortie de plusieurs dizaines de mW jusqu’à ~ 200 mW.Dans un second temps, nous avons développé des SESAMs à 1.55 µm. La région active est formée de puits quantiques InGaAsN/GaAs, couplés par effet tunnel à des plans GaAsN à recombinaison rapide. Des temps caractéristiques de recouvrement de l’absorption de quelques picosecondes à la dizaine de picoseconde sont ainsi mesurés.La résonance de la microcavité SESAM est ajustée de manière contrôlée grâce à des couches de phase spécifques épitaxiées en surface de la structure. La gravure sélective couche par couche des couches de phase permet d’accorder la profondeur de modulation et la dispersion de vitesse de groupe (GDD) de la structure SESAM.Finalement nous avons assemblé les structures SESAM et VECSEL dans une cavité à quatre miroirs pour obtenir un fonctionnement laser en régime de blocage de modes passif. Nous observons que la durée de l’impulsion de blocage de modes peut être réduite de plusieurs picosecondes (~ 10 ps), jusqu’à moins de la picoseconde (0.9 ps) en accordant la GDD de la structurre SESAM. / In a first step, we have developed and implemented VECSEL structures, aiming at maximizing the laser output power through a proper thermal management. The fabricated VECSEL chips contain an InP-based active region for emission at 1.55 µm. A hybrid metal-GaAs/AlAs Bragg mirror is used to achieve efficient dissipation of the heat generated in the active region. The semiconductor structure is integrated to various host substrates and the VECSEL performances are investigated numerically and experimentally. VECSELs with CVD diamond substrates have the best overall performance and are promising for large output power (> 500 mW), while electroplated copper substrate is demonstrated to be a flexible and cost-effective approach for thermal management in 1.55 µm OP-VECSEL in order to achieve output power of several tens of mW to ~ 200 mW. The second part of the work is devoted to the development of SESAM structures at 1.55 µm. The structures include an active region consisting of InGaAsN / GaAs quantum wells surrounding by GaAsN planes, allowing to achieve absorption relaxation time of few picoseconds. The SESAM microcavity resonance was adjusted via a selective etching of phase layers specifically designed to control the magnitude of both the modulation depth and the intra cavity group delay dispersion of the device.Finally, assembling VECSEL and SESAM chips in a cavity, we observe experimentally that the mode-locked pulse duration could be reduced from several picoseconds to less than one picosecond when the resonance and group delay dispersion of the SESAM microcavity are tuned.

Les exigences de plus en plus élevés concernant la qualité et propriétés de couches minces ont soutenu le développement de nouveaux procédés de pulvérisation. Ainsi, la décharge magnétron conventionnelle en courant continu, une des sources d’atomes la plus utilisée pour le dépôt de couches minces, a été améliorée par le couplage avec une décharge additionnelle de radio fréquence pour obtenir le nouveau procédé RF-IPVD (Radio Frequency-Ionized Physical Vapour Deposition). Ce procédé permet de générer un degré d’ionisation supérieur à celui dans la décharge magnétron classique, nécessaire pour contrôler les propriétés des couches minces. Un procédé alternatif pour augmenter d’avantage l’ionisation consiste à appliquer des impulsions haute puissance sur la cathode HPPMS (High Power Pulsed Magnetron Sputtering), pour des durés courtes de l’ordre de ųs ou dizaines de ųs. L’étude menée porte sur les phénomènes de pulvérisation et de transport des espèces du métal dans ces trois versions de la décharge magnétron par les moyens de spectroscopie laser à l’aide des diodes laser accordables. Le développement récent de ces diodes nous a permis de sonder les niveaux fondamentaux du Titane et de l’Aluminium, et de caractériser la dépendance spatiale de la densité et température ainsi que la fonction de distribution en vitesse de ces atomes. L’effet des paramètres clés, comme l’intensité du courant et la pression du gaz, est étudie et décrit pour la décharge magnétron conventionnelle. La distribution spatiale et angulaire de la fonction de distribution en vitesses a été mesurée dans la région devant la cible magnétron, afin de caractériser les flux du métal et leur comportement dans le volume de la décharge. L’étude sur les atomes du métal dans le procédé RF-IPVD est concentrée sur l’effet de la décharge additionnelle sur le dépeuplement du niveau fondamental. Une efficacité plus grande des processus d’ionisation est trouvée à plus haute pression et plus haute puissance RF injecté. On a montré aussi que les atomes affectés par les processus d’ionisation sont ceux thermalisées, tandis que la distribution de atomes rapides n’est quasiment pas affectés par la décharge additionnelle.Le diagnostic de la décharge pulsée a nécessité le développement d’une nouvelle procédure expérimentale, capable de suivre l’évolution de la densité et de la température des espèces neutres avec une résolution de l’ordre de la ųs. Cette procédure nous a servi pour décrire l’évolution spatio-temporel des atomes du métal (Ti et Al) et les atomes métastables d’Ar. Ces études offrent une vue globale sur le transport de atomes pulvérisés pendant la post décharge, ainsi qu’une description du fonctionnement de la décharge pulsé via la création des métastables d’Argon. / The higher requirements on the thin films quality have supported the development of new sputtering techniques. Thus, the conventional DC magnetron discharge, one of the most widely used source of atoms for thin film deposition, has been improved by the addition of an auxiliary radio frequency discharge - new technique called RF-IPVD (Radio Frequency -Ionized Physical Vapor Deposition). This technique highly increases the ionization degree compared to conventional magnetron discharge, which is necessary for a better control of the thin films properties. An alternative method to increase the ionization is based on the use of high power pulses on the cathode, HPPMS (High Power Pulsed Magnetron Sputtering), for short periods of time ranging from ųs to tens of ųs.The present study focuses on the sputtering phenomena and the transport of metal sputtered species in these three versions of the magnetron discharge, by means of laser spectroscopy using tunable laser diodes. The recent developments of these diodes have allowed to probe the fundamental levels of titanium and aluminum, and to characterize the spatial dependency of the density and temperature as well as the velocity distribution functions of these atoms. The effect of key discharge parameters, such as current intensity and gas pressure, is studied and described for the conventional magnetron discharge. The spatial and angular velocity distribution functions were measured in front of the magnetron target, in order to characterize the metal fluxes and their behavior in the discharge volume.The study on the metal atoms in the RF-IPVD process is focused on the effect of the additional discharge on the depopulation of the ground state level. Higher ionization efficiency is found at relatively high pressure and it increases with the injected RF power. It was also showed that the thermalized atoms are the ones involved in the ionization process, while the distribution of fast atoms is almost unaffected by the additional discharge.The diagnostics of the HPPMS discharge required the development of a novel experimental procedure, able to monitor the density and temperature of neutral species with a time resolution of ųs. This procedure was used to describe the spatiotemporal evolution of metal atoms (Ti and Al) and Ar metastable atoms. These studies provide an overview on the transport of sputtered atoms during the afterglow, and a description of the pulsed discharge operation, via the creation of metastable argon atoms.

Introdução: Estiramento muscular e outras desordens músculoesqueléticas são as principais causas que desabilitam atletas e praticantes de atividades físicas. Seu tratamento inclui AINES que desencadeiam vários efeitos adversos. O objetivo do estudo foi investigar os efeitos da Terapia Laser de Baixa Intensidade (810nm) sobre absorção do diclofenaco aplicado topicamente, além de investigar uma sinergia entre ambos. Métodos: Foram quantificadas concentrações plasmáticas de diclofenaco em diferentes tempos, com e sem irradiação do laser, em ratos Wistar fêmeas. Ratos foram submetidos à indução do estiramento muscular. Os grupos tratados receberam irradiação do Laser, antes da droga, 1 hora após a indução da lesão, para analisar índice funcional, estudo eletrofisiológico, expressão gênica RT-PCR de COX-1 e COX-2, PGE2 por espectrofotometria e histologia. Resultados/Discussão: A utilização do Laser de Baixa Potência aumentou a biodisponibilidade da droga e reduziu a inflamação e a lesão após estiramento experimental, conduzindo a uma melhora da atividade de caminhar. / Introduction: Stretch muscle and other musculoskeletal disorders are the main causes that disable the athlete and physically active practitioner. It´s treatment includes NSAIDs that trigger adverse effects. The aim of the study was to investigate the effect of Low Level Laser Therapy (810nm) on the absorption of topically applied diclofenac, and investigate a synergy between them. Methods: quantify the plasma concentrations of diclofenac in different times, with and without laser irradiation in Wistar female rats. Female Wistar rats were subjected to induction of muscle stretch. The groups received laser irradiation, prior to application of the drug, one hour after induction of the injury, to analyze the sciatic index functional, electrophysiological studies, gene expression by RT-PCR of COX-1 and COX-2, PGE2 by spectrophotometry and histology. Results/Discussion: The use of Low Level Laser Therapy increased the bioavailability of the drug and reduced inflammation and muscle damage after stretch experiment, leading to a significant improvement in walking activity.

O objetivo do presente estudo foi avaliar in situ o efeito da associação do verniz fluoretado ao laser de Er:YAG e ao laser Nd:YAG na permeabilidade da dentina radicular erodida. Quarenta e oito fragmentos de dentina radicular bovina, com dimensões 2x2x2 mm, foram submetidos a um desafio erosivo inicial com ácido cítrico (0,3%, pH 3,2), por duas horas, sob agitação e armazenados em saliva artificial por vinte e quatro horas. Posteriormente, os espécimes foram divididos em relação aos tratamentos: verniz fluoretado e não fluoretado e subdivididos conforme a irradiação: laser de Er:YAG (100mJ, 3Hz), laser de Nd:YAG (70mJ, 15 Hz) e não irradiado. Após um período de lead in (2 dias), os voluntários (n=8) utilizaram dispositivos palatinos contendo três espécimes que foram submetidos a desafios erosivos ex vivo, quatro vezes ao dia, com ácido cítrico (0,3%, pH 3,2), durante 90s, por cinco dias. Na primeira fase do experimento, metade dos voluntários utilizou dispositivos contendo fragmentos tratados com verniz fluoretado, verniz fluoretado + laser de Er:YAG e verniz fluoretado + laser de Nd:YAG. A outra metade utilizou verniz não fluoretado, verniz não fluoretado + laser de Er:YAG e verniz não fluoretado + laser de Nd:YAG. Depois de um período de wash-out (15 dias), os voluntários foram cruzados quanto aos tratamentos, caracterizando um experimento cross-over 2x2. Ao final de cada fase experimental, a permeabilidade dentinária foi avaliada. A ANOVA dois critérios e o teste complementar de Duncan revelaram uma diferença significativa entre os espécimes tratados com o verniz fluoretado (p=0,005), verniz fluoretado + laser de Er:YAG (p=0,014) e verniz fluoretado + laser de Nd:YAG (p=0,025), em comparação aos tratados com verniz não fluoretado. Observou-se que, independentemente da associação aos lasers (Er:YAG ou Nd:YAG), o verniz fluoretado foi capaz de promover a redução da permeabilidade da dentina radicular erodida. Não se observou efeito adicional com a associação dos tratamentos. / The present study aimed to evaluate in situ the effect of associating the fluoride varnish to Er:YAG or Nd:YAG laser at permeability of eroded root dentin. Forty-eight specimens of bovine root dentin (2x2x2mm) were subjected to initial erosive challenge with citric acid (0.3%, pH 3.2), for 2 hours under agitation and stored at artificial saliva, at 37&deg C, for 24 hours, followed by a remineralization period in artificial saliva. After that, specimens were divided according to the treatment: fluoride varnish and non-flouride varnish, and subdivided according to the irradiation: Er:YAG laser (100mJ, 3Hz), Nd:YAG laser (70mJ, 15Hz) and non-irradiated. After a lead-in period (2 days), 8 volunteers (n=8) wore a palatal device containing 3 specimens that was subjected to erosive challenges ex vivo, four times a day with citric acid (0.3%, pH3.2), for 90s, during 5 days. At the first experimental phase, half of volunteers wore devices containing specimens treated with fluoride varnish, fluoride varnish + Er:YAG laser and fluoride varnish + Nd:YAG laser, and the other half wore the specimens treated with non-fluoride varnish, non-fluoride varnish + Er:YAG laser and non-flouride varnish + Nd:YAG laser. After a wash-out period (15 days), volunteers were crossed to different treatment, characterizing a 2x2 cross-over experiment. At the end of each experimental phase, the dentinal permeability was evaluated. Two-way ANOVA and Duncans test revealed a significant difference between specimens treated with fluoride varnish (p=0,005), fluoride varnish + Er:YAG laser (p=0,014) and fluoride varnish + Nd:YAG (p=0,025) compared to specimens treated with no-fluoride varnish. It was observed that regardless of association to laser (Er:YAG or Nd:YAG), fluoride varnish was able to promote, in situ, the reduction of permeability of eroded root dentin, but no additional effect was observed when the treatments were associated.

A terapia a laser de baixa potência vem sendo utilizada para minimizar os efeitos maléficos da inflamação, bem como para acelerar a cicatrização dos tecidos lesados. Este estudo, visa observar as alterações causadas pela irradiação do laser diodo arsenieto de gálio (904nm), no tendão calcâneo em ratos. Foram utilizados 30 ratos da linhagem Wistar, com peso médio de 235g, divididos em dois grupos, um com 20 e outro com 10 animais. Todos os animais foram submetidos a tenotomia do tendão calcâneo direito. O tratamento com laser foi iniciado após 24 horas em um dos grupos, com a dose de 4 J/cm 2 ; e o outro grupo foi usado como controle. Utilizamos o método pontual, com a caneta do aparelho em contato direto com a pele do animal. Os dois grupos foram divididos em subgrupos, e os animais destes, sacrificados em períodos distintos, sendo no 8º e 15º pós-operatório. O tendão foi excisado e submetido a análise histológica pela microscopia de luz, onde foi observado a presença de células inflamatórias, fibroblastos, vascularização e deposição de colágeno. Houve diferença estatisticamente significante (p<0.05), entre controle e tratamento na deposição de colágeno e presença de células inflamatórias. Este estudo, sugestiona que a terapia a laser, proporciona a aceleração da cicatrização na tenotomia calcâneana em ratos, pelo aumento da deposição de colágeno, tanto na fase inicial como na tardia do tratamento. / Low-potency laser therapy has been used as a means of minimizing the hazardous effects of inflammation and accelerating healing in damaged tissues. This paper aims at observeving the alterations caused by diode AsGa (904nm), laser in the calcaneal tendon of rats. Thirty 235g (average weight) Wistar rats were divided into 2 groups – one with 20 and other with 10 animals, all of which underwent right calcaneal tendon tenotomy. One group started laser treatment at a dosege of 4 J/cm 2 24hours after surgery, the other being used as control. The punctual method was employed and the appliance pen kept in direct contact with animal's skin. Both groups were divided into subgroups, the animals of which were sacrificed in different times – on the 8 th and 15 th postoperative day, respectively. The tendon was excised and submitted to histology analysis using light microscopy, which revealed the presence of inflammatory cells, fibroblasts, vascularization and collagen deposition. There was a statistically significant difference (p <0.05) between the control and the treatment as far as collagen deposition at the presence of inflammatory cells are concerned. This study suggests that laser therapy accelerates healing in calcanean tenotomy in rats by increase collagen deposition both in the early and late parts of the treatment.

by Lee Yau-choi. / Title in Chinese: / Includes bibliographical references / Thesis (M.Ph.)--Chinese University of Hong Kong, 1986

by Chan Kam Kwong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references. / Abstract --- p.i / Acknowledgment --- p.iii / Contents --- p.iv / Abbreviation --- p.vi / List of Figures --- p.ix / List of Tables --- p.xii / Introduction --- p.xiii / Chapter 1. --- Basic Theories / Chapter 1.1 --- Static light scattering --- p.1 / Chapter 1.2 --- Dynamic light scattering --- p.11 / Chapter 1.3 --- LLS instrumentation --- p.19 / References --- p.20 / Chapter 2. --- "Light-Scattering Evidence of a ""Critical"" concentration for Polymer Coil Shrinking in Dilute Solution" / Chapter 2.1 --- Introduction --- p.23 / Chapter 2.2 --- Theoretical Background --- p.25 / Chapter 2.3 --- Experimental --- p.30 / Chapter 2.4 --- Results and Discussion --- p.31 / Chapter 2.5 --- Conclusions --- p.37 / Reference --- p.38 / Chapter 3. --- Experimental Study of the Spectral Distribution of the Light Scattered from Flexible Macromolecules in Very Dilute Solution / Chapter 3.1 --- Introduction --- p.40 / Chapter 3.2 --- Theoretical Background --- p.42 / Chapter 3.3 --- Experimental --- p.44 / Chapter 3.4 --- Results and Discussion --- p.45 / Chapter 3.5 --- Conclusions --- p.59 / References --- p.59 / Chapter 4. --- Characterization of Pauci-Chain Polystyrene Microlatices Prepared by Chemical Initiator / Chapter 4.1 --- Introduction --- p.61 / Chapter 4.2 --- Experimental --- p.63 / Chapter 4.3 --- Results and Discussion --- p.64 / Chapter 4.4 --- Conclusions --- p.81 / References --- p.82

Ti6Al4V is the most commonly used of the titanium alloys and is known for its high strength to weight ratio and superb corrosion resistance compared to conventional steels. Ti6Al4V is used in applications in the aerospace, biomedical, automotive, power generation and oil and gas fields. Laser metal deposition (LMD) is an additive manufacturing (AM) platform used to build 3-D metal shapes. LMD is one of the most researched topics within the laser processing field currently and is advancing continuously. The rapid growth in the AM field is driven by market demands to reduce manufacturing costs, shorter lead times and an increasing demand for customized products. One of the major challenges facing the production of Ti6Al4V components using LMD is the high resultant residual stresses, limiting build size due to delamination or distortion. At the commencement of this study, little data pertaining to the residual stress build up in larger LMD components was available. This research was conducted to create an understanding of the relationship between build height and surface residual stresses and how they influence the dimensional stability of a part. Additionally, the relationship between build height and static mechanical properties was analysed. The effects of laser power, scanning speed and powder mass flow rate on the deposition layer were evaluated. The number of defects and the deposition build height were evaluated to determine the optimum process parameters for multi-layer components. An increase in laser power resulted in an increase in build height for the parameter window selected for the study. Similarly, an increase in build height was observed with an increase in powder mass flow rate, while an increase in scanning speed resulted in a decrease in build height. As laser power and scanning speed had inverse effects on the build height, heat input was evaluated to determine the optimum combination of the 2 parameters. Multilayer samples were produced with a laser power setting of 1900 W, a scanning speed of 0.01 m/s and a powder mass flow rate of 8 g/min. Fully dense components were produced with no notable defects. These components were analysed to reveal the relationship between build height and surface residual stresses and showed that the minimum residual stress observed in a component was related to an actual height from the base and was not affected by the build height of the sample. Maximum residual stresses were observed closest to the base of the cylinder and the stresses were larger in larger samples for both hoop and longitudinal surface residual stress. The micro-hardness of the samples increased as build height increased. The tensile strength remained within constant range between 1080 MPa and 1050 MPa for all samples successfully tested. Brittle failures were observed on the upper sections of the larger samples, attributed to the high micro-hardness observed in these areas. The study successfully evaluated the relationship between build height and surface residual stresses as well as build height and static mechanical properties thereby increasing the knowledge within this field.