Engineering photonic and plasmonic light emission enhancement

Thesis (Ph.D.)--Boston UniversitySemiconductor photonic devices are a rapidly maturing technology which currently occupy multi-billion dollar markets in the areas of LED lighting and optical data communication. LEDs currently demonstrate the highest luminous efficiency of any light source for general lighting. Long-haul optical data communication currently forms the backbone of the global communication network. Proper design of light management is required for photonic devices, which can increase the overall efficiency or add new device functionality. In this thesis, novel methods for the control of light propagation and confinement are developed for the use in integrated photonic devices. The first part of this work focuses on the engineering of field confinement within deep subwavelength plasmonic resonators for the enhancement of light-matter interaction. In this section, plasmonic ring nanocavities are shown to form gap plasmon modes confined to the dielectric region between two metal layers. The scattering properties, near-field enhancement and photonic density of states of nanocavity devices are studied using analytic theory and 3D finite difference time domain simulations. Plasmonic ring nanocavities are fabricated and characterized using photoluminescence intensity and decay rate measurements. A 25 times increase in the radiative decay rate of Er:Si02 is demonstrated in nanocavities where light is confined to volumes as small as 0.01(λ/n)^3 . The potential to achieve lasing, due to the enhancement of stimulated emission rate in ring nanocavities, is studied as a route to Si-compatible plasmon-enhanced nanolasers. The second part of this work focuses on the manipulation of light generated in planar semiconductor devices using arrays of dielectric nanopillars. In particular, aperiodic arrays of nanopillars are engineered for omnidirectional light extraction enhancement. Arrays of Er:SiNx nanopillars are fabricated and a ten times increase in light extraction is experimentally demonstrated, while simultaneously controlling far-field radiation patterns in ways not possible with periodic arrays. Additionally, analytical scalar diffraction theory is used to study light propagation from Vogel spiral arrays and demonstrate generation of OAM. Using phase shifting interferometry, the presence of OAM is experimentally verified. The use of Vogel spirals presents a new method for the generation of OAM with applications for secure optical communications

Modeling of pulse-echo inspections of multi-layer panels containing delaminations

To meet the needs of counter insurgency operations the armor of tanks need to be lighter. This is accomplished by using a combination of materials: metals, composites, and ceramics. This multi-material composite armor using any combination of the above materials will need to be inspected for manufacturing error, shipping damage, and combat damage. Nondestructive inspection, particularly ultrasonic inspection, has a long history of successfully inspecting thick composite structures. To more easily develop inspection plans for many layered composites a computational model would be of use. A model of this type would need to have the ability to account for multiple material types and flaws that are larger than the beam size. Also, as a result of armor thickness any model would need to consider attenuation and effects of focused transducers. This was accomplishing by extending the Thompson{Gray Measurement Model for use with multiple layers at normal incidence to the transducer and large planar defects parallel to the layers. Material values of the armor and the characteristics of the transducers were determined for use in the model. The model results are compared to experimentally collected data to show agreement. The model is then used to determine the requirements of a new inspection plan through varying the frequency and focal length of the transducers

Components of a Financial Education Technology for Micro-entrepreneurs in Brazil

Purpose: This article designs a pedagogy and scalable technological solution to provide Brazilian micro- and small enterprises with guidance in business management habitdevelopment. Approach: The study demonstrates the need for formalized micro-entrepreneurship training and, given general financial education programs’ poor performance, considers micro-entrepreneurs’ fundamental educational needs. Findings: The analysis provides three fundamental components to consider in microentrepreneurship training design: content utility, communication intelligibility, and material interactivity. Research implications: The proposed pedagogy and virtual trainer technology suggest further study and development of optimal approaches to content utility, communication intelligibility, and material interactivity to improve micro-entrepreneurial habit-development and economic development

Common-Value Auctions with Liquidity Needs: An Experimental Test of a Troubled Assets Reverse Auction

We experimentally test alternative auction designs suitable for pricing and removing troubled assets from banks’ balance sheets as part of the financial rescue. Many individual securities or pools of securities are auctioned simultaneously. Securities that are widely held are purchased in auctions for individual securities. Securities with concentrated ownership are purchased as pools of related securities. Each bank has private information about its liquidity need and the true common value of each security. We study bidding behavior and performance of sealed-bid uniform-price auctions and dynamic clock auctions. The clock and sealed-bid auctions resulted in similar prices. However, the clock auctions resulted in substantially higher bank payoffs, since the dynamic auction enabled the banks to better manage their liquidity needs. The clock auctions also reduced bidder error. The experiments demonstrated the feasibility of quickly implementing simple and effective auction designs to help resolve the crisis.Auctions, financial auctions, financial crisis

Use of the Jung/Myers Model of Personality Types to Identify and Engage with Individuals at Greatest Risk of Experiencing Depression and Anxiety

Depression is the leading cause of ill health and disability worldwide. Objectives were (1) to determine the strength of the association between personality type with depression and anxiety using the Preferred Communication Style Questionnaire (PCSQ©) and the Four-Item Patient Health Questionnaire for Depression and Anxiety (PHQ-4) and (2) evaluate the extent to which severity of depression and anxiety is associated with personality type. Data were collected via a self-administered online survey of 10,500. Chi-square analysis compared personality types and depression and anxiety. Practical significance was determined by calculating the percentage-from-expected score based on established statistics reflecting each personality type’s percentage in the US population. Personality type was strongly associated with both depression and anxiety with certain types at significantly greater risk than others. Findings can improve the research and clinical community’s understanding of the specific risk factors and triggers for depression and anxiety, and result in more efficacious, tailored treatment options

The Effects of Exposure to Better Neighborhoods on Children: New Evidence from the Moving to Opportunity Experiment

The Moving to Opportunity (MTO) experiment offered randomly selected families housing vouchers to move from high-poverty housing projects to lower-poverty neighborhoods. We analyze MTO's impacts on children's long-term outcomes using tax data. We find that moving to a lower-poverty neighborhood when young (before age 13) increases college attendance and earnings and reduces single parenthood rates. Moving as an adolescent has slightly negative impacts, perhaps because of disruption effects. The decline in the gains from moving with the age when children move suggests that the duration of exposure to better environments during childhood is an important determinant of children's long-term outcomes.Economic

HIV-related<i>Pneumocystis jirovecii</i>pneumonia managed with caspofungin and veno-venous extracorporeal membrane oxygenation rescue therapy

Patients with pneumocystis pneumonia have a risk of progressing to acute respiratory failure necessitating admission to intensive care. The case described is of a patient with a newly diagnosed HIV infection presenting with pneumocystis pneumonia. Despite initiating the appropriate pharmacological treatment the patient’s clinical condition deteriorated, and required both rescue pharmacological therapy with echinocandins as well as respiratory support with extracorporeal membrane oxygenation therapy. The patient recovered well on ventilator and circulatory support despite a long weaning process complicated by sequelae common to pneumocystis pneumonia. Following initialisation of antiretroviral therapy and step-down from an intensive care setting, the patient required further prolonged hospital stay for rehabilitation and mental health support before being discharged. This case reviews the novel pharmacological therapies and respiratory support strategies used in cases of pneumocystis pneumonia, including the clinical and psychological sequelae that may follow