Historically ceramic crystal laser material has had disadvantages compared to single crystal laser material. However, progress has been made in the last decade and a half to overcome the disadvantages associated with ceramic crystal. Today, because of the promise of ceramic crystal as a high power laser material, investigation into its properties, both physical and optical, is warranted and important. Thermal expansion was measured in this thesis for Nd:YAG (yttrium aluminum garnet) ceramic crystal using an interferometric method. The interferometer employed a spatially filtered HeNe at 633 nm wavelength. Thermal expansion coefficients measured for the ceramic crystal samples were near the reported values for single crystal Nd:YAG. With a similar experimental setup as that for the thermal expansion measurements, dn/dT for ceramic crystal Nd:YAG was measured and found to be slightly higher than the reported value for single crystal. Depolarization loss due to thermal gradient induced stresses can limit laser performance. As a result this phenomenon was modeled for ceramic crystal materials and compared to single crystals for slab and rod shaped gain media. This was accomplished using COMSOL Multiphysics, and MATLAB. Results indicate a dependence of the depolarization loss on the grain size where the loss decreases with decreased grain size even to the point where lower loss may be expected in ceramic crystals than in single crystal samples when the grain sizes in the ceramic crystal are sufficiently small. Deformation-induced thermal lensing was modeled for a single crystal slab and its relevance to ceramic crystal is discussed. Data indicates the most notable cause of deformation-induced thermal lensing is a consequence of the deformation of the top and bottom surfaces. Also, the strength of the lensing along the thickness is greater than the width and greater than that due to other causes of lensing along the thickness of the slab. Emission spectra, absorption spectra, and fluorescence lifetime were measured for Nd:YAG ceramic crystal and Yb:Lu2O3 ceramic crystal. No apparent inhomogeneous broadening appears to exist in the Nd:YAG ceramic at low concentrations. Concentration and temperature dependence effects on emission spectra were measured and are presented. Laser action in a thin disk of Yb:Y2O3 ceramic crystal was achieved. Pumping was accomplished with a fiber coupled diode laser stack at 938 nm. A slope efficiency of 34% was achieved with maximum output energy of 28.8 mJ/pulse.

In order to meet the needs of the generations to come and to achieve the global target of maximum climate change of 1.5 degrees, we need to transform the way the society consumes natural resources. The purpose of this research is to effectively align the needs of the businesses and customers alike to accelerate a market-driven resource efficiency. We also intended to investigate what the opportunities presented to businesses are, in order to achieve environmental and economic sustainability by extending the product lifetime and improving accessibility of spares/repairs/upgrades, etc. for their products. We performed an extensive review of literature in the past two decades which describe product lifetime, obsolescence of products and the various reasons of obsolescence in the larger picture. The study is a mixed approach as we gathered data from the partner businesses by way of semi-structured interviews at the management level. We carried out a survey with a potential consumer group of these products and analysed the requirements and habits of the market. Our findings suggest that the primary driving causes for optimizing the product lifetimes of the products have been ethical and social responsibilities of the businesses. Businesses acknowledge that legislative and market pressure has increased over the past half-decade but hasn’t been enough to motivate the investments required to restructure products and business models. Businesses need to improve the statistical data they acquire from products after they have been sold, in order to facilitate the streamlining of the reverse supply chains. Lastly, we have found that the top management is committed and engaged to change the way the business functions, but the ground functions are either not aware or trained to effectively implement the changes. Future research could investigate the readiness of businesses to transition to a more closed-loop business model by way of improving information flow through the lifetime of the product. / För att bemöta kraven hos de kommande generationer och för att uppnå det globala målet om en maximal klimatförändring på 1,5 grader, måste det ske en förändring på hur samhället konsumerar naturresurser. Syftet med denna forskning och studie är att effektivt anpassa behoven hos såväl kunden som företag för att påskynda en marknadsdriven resurseffektivitet. Med denna studie har vi också för avsikt att undersöka vilka möjligheter som erbjuds till företag, för att uppnå miljömässig och ekonomisk hållbarhet genom att förlänga produktens livslängd och förbättra cängligheten för reservdelar/reparationer/uppgraderingar etc. av deras produkter. Vi gjorde en omfattande litteraturgenomgång av forskning under de senaste två decennierna som beskriver produktens livslängd, produkters inkurans och de olika orsakerna till inkurans i den större bilden. Detta hjälpte oss att ta fram en konkret definition av produktens livslängd och hur den kan förbättras med bättre material, design och ökade återvinnings aktiviteter på produktnivå. Våra resultat tyder på att de främsta drivande orsakerna till att optimera produkt livslängden för produkterna i fråga har varit företagens etiska och sociala ansvar. Företagen erkänner att lagstiftnings- och marknads trycket har ökat under de senaste 5 åren, men det har inte varit tillräckligt för att motivera de investeringar som krävs för att omstrukturera produkter och affärsmodeller. Företag måste förbättra de statistiska uppgifter som de skaffar från produkter efter att de har sålts, för att underlätta effektiviseringen. Slutligen har vi funnit att den högsta ledningen är engagerad i att förändra hur verksamheten fungerar, men markfunktionerna är antingen inte medvetna eller utbildade för att effektivt implementera förändringarna. Framtida forskning skulle kunna undersöka företagens beredskap att övergå till en mer sluten affärsmodell genom att förbättra informationsflödet genom produktens livslängd.

Internet of Things (IoT) refers to the interconnection of uniquely identifiable smart devices which enables them to participate more actively in everyday life. Among large-scale applications, machine-type communications (MTC) supported by cellular networks will be one of the most important enablers for the success of IoT. The existing cellular infrastructure has been optimized for serving a small number of long-lived human-oriented communications (HoC) sessions, originated from smartphones whose batteries are charged in a daily basis. As a consequence, serving a massive number of non-rechargeable machine-type devices demanding a long battery lifetime is a big challenge for cellular networks. The present work is devoted to energy consumption modeling, battery lifetime analysis, and lifetime-aware network design for massive MTC services over cellular networks. At first, we present a realistic model for energy consumption of machine devices in cellular connectivity, which is employed subsequently in deriving the key performance indicator, i.e. network battery lifetime. Then, we develop an efficient mathematical foundation and algorithmic framework for lifetime-aware clustering design for serving a massive number of machine devices. Also, by extending the developed framework to non-clustered MTC, lifetime-aware uplink scheduling and power control solutions are derived. Finally, by investigating the delay, energy consumption, spectral efficiency, and battery lifetime tradeoffs in serving coexistence of HoC and MTC traffic, we explore the ways in which energy saving for the access network and quality of service for HoC traffic can be traded to prolong battery lifetime for machine devices. The numerical and simulation results show that the proposed solutions can provide substantial network lifetime improvement and network maintenance cost reduction in comparison with the existing approaches. / <p>QC 20161103</p>

Nanophotonische Systeme sind eine leistungsfähige Plattform für die Untersuchung von Licht-Materie-Wechselwirkungen. In solchen Systemen bricht die übliche Beschreibung einer elektromagnetischen Welle als eine Welle, die in Bezug auf ihre Ausbreitungsrichtung transversal polarisiert ist, zusammen. Dies ist auf die Einengung der geführten Lichtfelder zurückzuführen, welche zu einer longitudinalen Komponente der elektromagnetischen Felder führt. In dieser Arbeit nutzen wir dies in Verbindung mit unterschiedlichen Kopplungsstärken von Cäsiumatomen an \sigma^- und \sigma^+ polarisiertes Licht, um das Prinzip neuartiger nicht-reziproker optischer Bauelemente zu demonstrieren. Im ersten Teil dieser Arbeit demonstrieren wir die nicht-reziproke Verstärkung von fasergeführtem Licht mit Hilfe von Raman-Verstärkung durch spinpolarisierte Cäsiumatome, die an die Nanofasertaille eines verjüngten Faserabschnitts gekoppelt sind. Wir zeigen, dass unser neuartiger Mechanismus kein externes Magnetfeld benötigt und dass wir die Richtung der Verstärkung vollständig über den atomaren Spinzustand kontrollieren können. Darüber hinaus nutzen wir die chirale Licht-Materie-Wechselwirkung in unserem System, um einen nicht-reziproken antisymmetrischen optischen Phasenschieber zu realisieren. Diese Ergebnisse tragen zur Etablierung einer neuen Klasse von spin-gesteuerten, nicht-reziproken integrierten optischen Bauelementen bei und können den Aufbau komplexer optischer Netzwerke vereinfachen. In einem weiteren Forschungsprojekt tragen wir zum grundlegenden Verständnis von Atomen bei, indem wir die Lebensdauer eines angeregten Cäsiumzustands präzise messen. Wir messen die Lebensdauer des Cäsium 5D_{5/2} Zustands im freien Raum. Wir finden eine Lebensdauer von 1353(5) ns, die mit einer aktuellen theoretischen Vorhersage übereinstimmt. Unsere Messung trägt dazu bei, eine seit langem bestehende Unstimmigkeit zwischen verschiedenen experimentellen und theoretischen Ergebnissen zu beseitigen. / Nanophotonic systems are a powerful platform for the study of light-matter interactions. In such systems, the common description of an electromagnetic wave as a wave that is transversely polarized with respect to its propagation direction breaks down. This is due to the tight confinement of the guided light fields, which leads to a longitudinal component of the electromagnetic fields. In this thesis, we use this in conjunction with different coupling strengths of cesium atoms to \sigma^- and \sigma^+ polarized light to provide proof-of-principle demonstrations of novel non-reciprocal optical devices. In the first part of this thesis, we demonstrate non-reciprocal amplification of fiber-guided light using Raman gain provided by spin-polarized cesium atoms that are coupled to the nanofiber waist of a tapered fiber section. We show that our novel mechanism does not require an external magnetic field and that it allows us to fully control the direction of amplification via the atomic spin state. Moreover, we use the chiral light-matter interaction in our system to implement a non-reciprocal antisymmetric optical phase shifter. These results contribute to establishing a new class of spin-controlled, non-reciprocal integrated optical devices and may simplify the construction of complex optical networks. In an additional research project, we also contribute to the fundamental understanding of atoms by precisely measuring the lifetime of an excited cesium state. We measure the lifetime of the cesium 5D_{5/2} state in free space. We find a lifetime of 1353(5) ns, in agreement with a recent theoretical prediction. Our measurement contributes to resolving a long-standing disagreement between several experimental and theoretical results.

[pt] Os cabos ópticos submarinos estão distribuídos por boa parte dos oceanos ao redor do globo terrestre. Esses cabos começaram a ser instalados com maior intensidade na década de 90, apesar de o primeiro cabo submarino óptico ter sido instalado em 1982 nas ilhas Canárias. Atualmente a importância dos cabos ópticos submarinos é de grande relevância para as comunicações mundiais e vem crescendo muito ao longo do tempo com a demanda por serviços de internet, liderada hoje pelas grandes empresas de tecnologia e de exploração de mídia social, tais como Google, Amazon, Meta, etc. Hoje cerca de 99 por cento de todo o tráfego da comunicação mundial da internet passa pelos cabos submarinos. Os custos para implantação desses cabos são muito altos e, portanto, prover alternativas para a ampliação da sua duração para um período maior do que a sua expectativa de vida útil representa um ganho considerável para todos. Considera-se atualmente pelos fabricantes e organismos de padronização internacional, como o ITU-T (União Internacional de Telecomunicações), uma expectativa média de vida útil de 25 anos. Esta expectativa de vida útil dada para os cabos ópticos foi a principal motivação para o desenvolvimento dessa pesquisa, cujos objetivos visam apresentar evidências que indiquem que a tendência de vida útil dos cabos ópticos submarinos pode superar os 25 anos previstos, e dessa forma contribuir para o atendimento da crescente demanda por transmissão de dados no mundo impulsionada pelos serviços de Internet. A metodologia adotada foi coletar dados de medições com o OTDR em cabos ópticos submarinos ao longo de 24 anos e avaliar a degradação sofrida pelo coeficiente de atenuação em dB/km ao longo do tempo das fibras ópticas dos cabos em operação, e comparar com a degradação sofrida pelos cabos sobressalentes, e avaliar também a degradação das perdas nas emendas submarinas e a sua correlação com a profundidade de instalação no mesmo período. As análises foram realizadas através da avaliação das curvas em arquivos na extensão .Sor obtidas com as medições realizadas pelo OTDR. Os resultados obtidos demostraram que os cabos ópticos em operação sofreram degradações compatíveis com os valores esperados e dados pelo ITU-T, mas também mostraram através da análise de curvas de tendência, que a degradação tem um comportamento logarítmico, e a projeção da curva de tendência para os próximos anos indicou que esses cabos poderão continuar em operação por muito mais anos do que os 25 anos, dados como limite anterior. Foi observado também que a penalidade de potência dada pela perda nas emendas é muito superior a degradação somente nas fibras ópticas, que existe uma correlação positiva entre a profundidade das caixas de emenda e a degradação na emenda e que os cabos sobressalentes degradam muito mais que os cabos em operação. / [en] Submarine optical cables are distributed over most of the oceans around the globe.These cables were installed with greater intensity in the 1990s, despite the fact that the firstoptical submarine cable was installed in 1982 in the Canary Islands. Currently, theimportance of submarine optical cables is very relevant for world communications and hasbeen growing a lot over time with the demand for internet services, led today by largetechnology and social media companies such as Google, Amazon, Meta, etc. Today around 99 percent of all world internet communication goes through undersea cables. The costs forimplanting these cables are very high and, therefore, to provide alternatives for optimizingtheir use by extending their duration for a period longer than their expected useful life,given by international standardization bodies, such as the ITU-T (InternationalTelecommunications Union), and by the manufacturers, which currently is 25 years, is ahuge gain for everyone. The life expectancy given for optical cables was the mainmotivation for the development of this research, whose objectives aim to present evidencethat indicates that the useful life trend of submarine optical cables can reach much morethan the 25 years predicted and in this way contribute to meeting the growing demand fordata transmission in the world, driven by Internet services. The adopted methodology wasto collect measurement data with the OTDR in submarine optical cables over 24 years andto evaluate the degradation suffered by the attenuation coefficient in dB/Km over time ofthe optical fibers of the cables in operation and to compare with the degradation sufferedby the spare cables, and also evaluate the degradation of the losses in the underwater splicesand its correlation with the depth of installation in the same period. The analyzes werecarried out by evaluating the .Sor curves obtained with the measurements performed by theOTDR. The conclusions showed that the optical cables in operation suffered degradationscompatible with the expected values and given by the ITU-T, but also showed through theanalysis of trend curves, that the degradation has a logarithmic behavior, and the projectionof the trend curve for the coming years indicated that these cables could continue to operatefor many more years than the 25 years given as the previous limit. It was also observed thatthe power penalty given by the loss in the splices is much higher than the degradation inthe optical fibers alone, that there is a positive correlation between the depth of the spliceboxes and the degradation in the splice, and that the spare cables degrade much more thanthe cables in operation.

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Background and Aims: In India, alcohol per capita consumption (APC) has substantially increased over the past 2 decades. Although consumption does vary across the country, consistent state-level data are lacking. We aimed to identify all state-level alcohol exposure estimates since 2000 to (i) model consistent current drinking (CD) (12 months) prevalence estimates for all 36 states/union territories (UT) in 2019 and (ii) compare state-level CD trends with national-level APC trends. Design: A systematic review for studies on the Indian state-level prevalence of CD, lifetime abstinence (LA), alcohol use disorders (AUD) or the quantity of alcohol consumed among current drinkers (QU) was conducted. Subsequently, statistical modelling was applied. Setting: Data were collected and modelled for all Indian states/UTs. Participants: Studies since 2000 referring to the general adult population (≥15 years) of at least one Indian state/UT were eligible. The total sample size covered was 29 600 000 (males: females, 1:1.6). Measurements: Results on LA, AUD and QU were summarized descriptively. For (i) the state-, sex- and age-specific CD prevalence was estimated using random intercept fractional response models. For (ii) random intercept and slope models were performed. Findings: Of 2870 studies identified, 30 were retained for data extraction. LA, AUD and QU data were available for 31, 36 and 12 states/UTs, respectively. CD model estimates ranged from 6.4% (95% CI = 2.1%–18.1%; males) in Lakshadweep and 1.3% (95% CI = 0.7%–2.6%; females) in Delhi to 76.1% (95% CI = 68.1%–82.6%; males) and 63.7% (95% CI = 49.4%–75.7%; females) in Arunachal Pradesh. Over time, CD decreased in most states/UTs in the observed data, contradicting increasing national-level APC trends. Conclusions: Alcohol use (measured as consistent current drinking) in India has large regional variations, with alcohol consumption being most prevalent in the North-East, Chhattisgarh, Telangana, Himachal Pradesh, Punjab and Jharkhand.