Solar Cell Light Trapping beyond the Ray Optic Limit

In 1982, Yablonovitch proposed a thermodynamic limit on light trapping within homogeneous semiconductor slabs, which implied a minimum thickness needed to fully absorb the solar spectrum. However, this limit is valid for geometrical optics but not for a new generation of subwavelength solar absorbers such as ultrathin or inhomogeneously structured cells, wire-based cells, photonic crystal-based cells, and plasmonic cells. Here we show that the key to exceeding the conventional ray optic or so-called ergodic light trapping limit is in designing an elevated local density of optical states (LDOS) for the absorber. Moreover, for any semiconductor we show that it is always possible to exceed the ray optic light trapping limit and use these principles to design a number of new solar absorbers with the key feature of having an elevated LDOS within the absorbing region of the device, opening new avenues for solar cell design and cost reduction

Light trapping beyond the 4n^2 limit in thin waveguides

We describe a method for determining the maximum absorption enhancement in thin film waveguides based on optical dispersion relations. For thin film structures that support one, well-confined guided mode, we find that the absorption enhancement can surpass the traditional limit of 4n^2 when the propagation constant is large and/or the modal group velocity is small compared to the bulk value. We use this relationship as a guide to predicting structures that can exceed the 4n^2 light trapping limit, such as plasmonic and slot waveguides. Finally, we calculate the overall absorption for both single and multimode waveguides, and show examples of absorption enhancements in excess of 4n^2 for both cases

Fundamental results from microgravity cell experiments with possible commericial applications

Some of the major milestones are presented for studies in cell biology that were conducted by the Soviet Union and the United States in the upper layers of the atmosphere and in outer space for more than thirty-five years. The goals have changed as new knowledge is acquired and the priorities for the use of microgravity have shifted toward basic research and commercial applications. Certain details concerning the impact of microgravity on cell systems is presented. However, it needs to be emphasized that in planning and conducting microgravity experiments, there are some important prerequisites not normally taken into account. Apart from the required background knowledge of previous microgravity and ground-based experiments, the investigator should have the understanding of the hardware as a physical unit, the complete knowledge of its operation, the range of its capabilities and the anticipation of problems that may occur. Moreover, if the production of commercial products in space is to be manifested, data obtained from previous microgravity experiments must be used to optimize the design of flight hardware

Cells in Space

Discussions and presentations addressed three aspects of cell research in space: the suitability of the cell as a subject in microgravity experiments, the requirements for generic flight hardware to support cell research, and the potential for collaboration between academia, industry, and government to develop these studies in space. Synopses are given for the presentations and follow-on discussions at the conference and papers are presented from which the presentations were based. An Executive Summary outlines the recommendations and conclusions generated at the conference

Method and Meaning: Selections from the Gettysburg College Collection

What is art historical study and how it should be carried out are fundamental questions the exhibition Method and Meaning: Selections from the Gettysburg College Collection intends to answer. This student-curated exhibition is an exciting academic endeavor of seven students of art history majors and minors in the Art History Methods course. The seven student curators are Shannon Callahan, Ashlie Cantele, Maura D’Amico, Xiyang Duan, Devin Garnick, Allison Gross and Emily Zbehlik. As part of the class assignment, this exhibition allows the students to explore various art history methods on individual case studies. The selection of the works in the exhibition reflects a wide array of student research interests including an example of 18th century Chinese jade chime stone, jade and bronze replicas of ancient Chinese bronze vessels, a piece of early 20th century Chinese porcelain, oil paintings by Pennsylvania Impressionist painter Fern Coppedge, prints by Salvador Dalí and by German artist Käthe Kollwitz, and an early 20th century wood block print by Japanese artist Kawase Hasui. [excerpt]https://cupola.gettysburg.edu/artcatalogs/1014/thumbnail.jp

The Political Economy of Myanmar's Transition

This is an Author's Original Manuscript of an article whose final and definitive form, the Version of Record, has been published in the JOURNAL OF CONTEMPORARY ASIA, 07 Feb 2013, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/00472336.2013.764143.Since holding elections in 2010, Myanmar has transitioned from a direct military dictatorship to a formally democratic system and has embarked on a period of rapid economic reform. After two decades of military rule, the pace of change has startled almost everyone and led to a great deal of cautious optimism. To make sense of the transition and assess the case for optimism, this article explores the political economy of Myanmar's dual transition from state socialism to capitalism and from dictatorship to democracy. It analyses changes within Myanmar society from a critical political economy perspective in order to both situate these developments within broader regional trends and to evaluate the country's current trajectory. In particular, the emergence of state-mediated capitalism and politico-business complexes in Myanmar's borderlands are emphasised. These dynamics, which have empowered a narrow oligarchy, are less likely to be undone by the reform process than to fundamentally shape the contours of reform. Consequently, Myanmar's future may not be unlike those of other Southeast Asian states that have experienced similar developmental trajectories

Ray-based calculations of backscatter in laser fusion targets

A 1D, steady-state model for Brillouin and Raman backscatter from an inhomogeneous plasma is presented. The daughter plasma waves are treated in the strong damping limit, and have amplitudes given by the (linear) kinetic response to the ponderomotive drive. Pump depletion, inverse-bremsstrahlung damping, bremsstrahlung emission, Thomson scattering off density fluctuations, and whole-beam focusing are included. The numerical code DEPLETE, which implements this model, is described. The model is compared with traditional linear gain calculations, as well as "plane-wave" simulations with the paraxial propagation code pF3D. Comparisons with Brillouin-scattering experiments at the OMEGA Laser Facility [T. R. Boehly et al., Opt. Commun. 133, p. 495 (1997)] show that laser speckles greatly enhance the reflectivity over the DEPLETE results. An approximate upper bound on this enhancement, motivated by phase conjugation, is given by doubling the DEPLETE coupling coefficient. Analysis with DEPLETE of an ignition design for the National Ignition Facility (NIF) [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Technol. 26, p. 755 (1994)], with a peak radiation temperature of 285 eV, shows encouragingly low reflectivity. Re-absorption of Raman light is seen to be significant in this design.Comment: 16 pages, 19 figure

Technology, creativity and the media in engineering China’s future

Political, economic and intellectual elites in China have for some time been in the grip of ‘futurology’ as they reflect on thirty years’ of extraordinary economic development and ask ‘what next’? China has a dream, in fact it has many visions of what it may become, reflecting robust debate and competition to define the nation’s future course of reform and development (Callahan, 2013). On assuming the top party and state positions in October 2012 Xi Jinping quickly unveiled the China Dream (Zhonguomeng) as the maxim for his leadership. Although specification of what the dream will entail is yet to be fully explicated, one thing is certain: low-cost production and outsourcing more advanced economies’ dirty jobs is neither the subject of China’s dream nor is it any longer considered the means to delivering it. The ‘world’s factory’ model that facilitated China’s remarkable economic growth has come under pressure from all sides, as the party acknowledges its unsustainability and people deal with the consequences. Party elites and policymakers have taken significant steps toward a different and more sustainable model to secure long term growth and it is hoped that low-end manufacturing will give way to a service based economy and consumer culture facilitated by urbanization, migration and developing greater creative capacity. These plans are underpinned by the ambition to become an ‘innovative nation’ (chuangxinxing de guojia), to develop soft power resources to go with economic might, and to raise the ‘quality’ (suzhi) of the people. As the three books covered in this review essay demonstrate, technology, culture and the media are closely implicated, and closely controlled, in the Chinese state’s quest for development