Full-Day Kindergarten in California: Lessons From Los Angeles

Analyzes the impact of full-day kindergarten on academic, grade retention, and English fluency outcomes through second grade by school and student characteristics, with a focus on the economically disadvantaged and English learners. Outlines implications

Optomechanical creation of magnetic fields for photons on a lattice

We propose using the optomechanical interaction to create artificial magnetic fields for photons on a lattice. The ingredients required are an optomechanical crystal, i.e. a piece of dielectric with the right pattern of holes, and two laser beams with the right pattern of phases. One of the two proposed schemes is based on optomechanical modulation of the links between optical modes, while the other is an lattice extension of optomechanical wavelength-conversion setups. We illustrate the resulting optical spectrum, photon transport in the presence of an artificial Lorentz force, edge states, and the photonic Aharonov-Bohm effect. Moreover, wWe also briefly describe the gauge fields acting on the synthetic dimension related to the phonon/photon degree of freedom. These can be generated using a single laser beam impinging on an optomechanical array

Oil and geopolitics: the oil crises of the 1970s and the Cold War

Examination of the geopolitics of oil in the 1970s provides important insights into the nature and dynamics of the Cold War. Possession of ample domestic oil supplies and the ability to ensure access to foreign oil reserves were significant elements in the power position of the United States in its Cold War competition with the Soviet Union. U.S. oil production peaked in 1970,however, making the United States increasingly dependent on oil imports and ending its ability to provide oil to its allies during supply interruptions. At the same time, economic nationalism and war and revolution in the Middle East led to disruptions in supply and sharp increases in oil prices in 1973-74 and again in 1978-80. In contrast, the Soviet Union overtook the United States as the world’s leading oil producer in the 1970s, and the windfall from higher oil prices helped support Soviet military and economic power and involvement in the Third World. The oil crises raised questions about the ability of the United States to ensure access to Middle East oil, heightened concerns about the dangers of Western dependence on Third World resources, and fed fears that the Soviet Union was winning the Cold War. Although the oil crises of 1970s initially harmed the United States and its allies and contributed to the demise of détente, they also set in motion changes that led to the end of the Cold War

Rayleigh scattering, mode coupling, and optical loss in silicon microdisks

High refractive index contrast optical microdisk resonators fabricated from silicon-on-insulator wafers are studied using an external silica fiber taper waveguide as a wafer-scale optical probe. Measurements performed in the 1500 nm wavelength band show that these silicon microdisks can support whispering-gallery modes with quality factors as high as 5.2 x 10^5, limited by Rayleigh scattering from fabrication induced surface roughness. Microdisks with radii as small as 2.5 microns are studied, with measured quality factors as high as 4.7 x 10^5 for an optical mode volume of 5.3 cubic wavelengths in the material.Comment: 4 pages, 2 figures; contains minor correction to doublet splitting theor

Analysis of the extraterrestrial life detection problem

Analysis of extraterrestrial life detection proble

Ideality in a fiber-taper-coupled microresonator system for application to cavity quantum electrodynamics

The ability to achieve near lossless coupling between a waveguide and a resonator is fundamental to many quantum-optical studies as well as to practical applications of such structures. The nature of loss at the junction is described by a figure of merit called ideality. It is shown here that under appropriate conditions ideality in excess of 99.97% is possible using fiber-taper coupling to high-Q silica microspheres. To verify this level of coupling, a technique is introduced that can both measure ideality over a range of coupling strengths and provide a practical diagnostic of parasitic coupling within the fiber-taper-waveguide junction

Use of combinatorial analysis for the study of new material for solar cells applications

This paper presents a combinatorial method for the deposition and characterization of new metallic precursors for photovoltaic materials. Onedimensional thin film alloy “libraries” were electrodeposited on Mo-coated glass. The library elements were deposited in two consecutive baths and then heated in a reducing atmosphere to promote interdiffusion of the elements. At the end of this process, the libraries possessed a composition gradient along their lengths, with single elements at their two opposite ends and one or more alloys and/or a solid state solution in between. This continuous range of compositions can therefore be considered a collection of specific precursors that can be interrogated by examining their corresponding locations, with the crystallographic structure along the library changing in accordance with the phase diagram for the metals. The libraries were then sulphurised or selenised by heating in a sulphur-rich or selenium rich atmosphere; this converted the metallic precursors in a continuous range of materials, candidates for potential solar cells absorbers. The libraries were analysed by X-ray diffraction and energy dispersive X-ray spectrometry. The X-ray diffraction results show phase changes across the libraries, which can be correlated with the original precursor concentration at that particular p

Phonon laser action in a tunable, two-level photonic molecule

The phonon analog of an optical laser has long been a subject of interest. We demonstrate a compound microcavity system, coupled to a radio-frequency mechanical mode, that operates in close analogy to a two-level laser system. An inversion produces gain, causing phonon laser action above a pump power threshold of around 50 $\mu$W. The device features a continuously tunable, gain spectrum to selectively amplify mechanical modes from radio frequency to microwave rates. Viewed as a Brillouin process, the system accesses a regime in which the phonon plays what has traditionally been the role of the Stokes wave. For this reason, it should also be possible to controllably switch between phonon and photon laser regimes. Cooling of the mechanical mode is also possible.Comment: 4 pages, 4 figure