Stacked dielectric gratings for sub-wavelength surface field synthesis

A method is developed to enhance the amplitudes of the non-propagating evanescent orders of resonant dielectric gratings. The origin of these resonances is analyzed in detail. The method relies on interactions between stacked gratings with different periods, and so a formalism is developed to model such stacks mathematically. In addition, a theoretical approach is developed to design gratings that enhance or blaze desired orders. These orders, controlled independently by incident fields from different angles, interfere and are optimized to produce steerable sub-Rayleigh field concentrations on a surface. These spots may function as a virtual scanning probe for non-invasive sub-Rayleigh microscopy. Optimization is conducted using a Monte Carlo Markov chain, and spots are generated which are both 1 order of magnitude narrower than the free space Rayleigh limit and robust to noise in the incident fields. © 2010 Optical Society of America

Blazing evanescent grating orders: A spectral approach to beating the Rayleigh limit

We develop a way to enhance the amplitudes of the nonpropagating evanescent orders of resonant dielectric gratings. We use this blazing to design gratings with spectra tailored to generate steerable sub-Rayleigh field concentrations on a surface. We investigate the enhancement and customization of evanescent fields necessary to create a virtual and passive scanning probe with no moving parts. Spot size can be decreased 1 order of magnitude below the free-space Rayleigh limit. © 2010 Optical Society of America

Public Policy and Disaster Justice

Issues of unequal vulnerability to disasters, and uneven access to assistance and decision making, are core challenges in disaster policy, but not generally explored from a justice perspective. This chapter considers justice through six standard lenses of public policy: (1) whether justice-relevant decisions are a matter for public policy or more value-rich politics; (2) if the former, where in the policy process they can be attended to; (3) which entity has responsibility over the matter; (4) in addition to formal responsibilities, what actors outside of government contribute to justice or injustices; (5) whether justice is a matter of disaster policy, or another policy sector; and (6) whether enhancement of existing policies can provide remedy, or new mechanisms are needed

The rains are disappointing us: dynamic vulnerability and adaptation to multiple stressors in the Afram Plains, Ghana

Adaptation, Afram plains, Africa, Agriculture, Community, Ghana, Food security, Water, Vulnerability,