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Geometric complexity theory (GCT) is an approach towards the P vs. NP and related problems. The article [GCTflip] describes its defining strategy, called the flip, to resolve the self referential paradox, which is the root difficulty in these problems. This article describes an approach based on positivity hypotheses in algebraic geometry and representation… (More)

In an earlier paper we introduced the concept of the perfect lens which focuses both near and far electromagnetic fields, hence attaining perfect resolution. Here we consider refinements of the original prescription designed to overcome the limitations of imperfect materials. In particular we show that a multilayer stack of positiveand… (More)

In the past few years, new developments in structured electromagnetic materials have given rise to negative refractive index materials which have both negative dielectric permittivity and negative magnetic permeability in some frequency ranges. The idea of a negative refractive index opens up new conceptual frontiers in photonics. One much-debated example… (More)

- Govind Dayal, Sri Ramakrishna
- Optics express
- 2012

Simple designs for polarization independent, metamaterial absorbers at mid-infrared wavelengths and over wide angle of incidence are evaluated computationally. One design consists of an array of circular metallic disks separated from a continuous metallic film by a dielectric film, and shows over 99.9% peak absorbance and a resonant bandwidth of about 0.2… (More)

- Sri Ramakrishna, Olivier J. F. Martin
- Optics letters
- 2005

We address the general issue of resolving the wave vector in complex electromagnetic media including negative refractive media. This requires us to make a physical choice of the sign of a square root imposed merely by conditions of causality. By considering the analytic behavior of the wave vector in the complex plane, it is shown that there are a total of… (More)

It has been shown that a slab of materials with refractive index n = −1 behaves like a perfect lens focusing all light to an exact electromagnetic copy of an object. The original lens is limited to producing images the same size as the object, but here we generalize the concept so that images can be magnified. For two-dimensional systems, over distances… (More)

A slab of negatively refracting material, thickness d , can focus an image at a distance 2d from the object. The negative slab cancels an equal thickness of positive space. This result is a special case of a much wider class of focusing: any medium can be optically cancelled by an equal thickness of material constructed to be an inverted mirror image of the… (More)

- Jhuma Dutta, Sri Ramakrishna
- Nanotechnology
- 2015

Gratings with slanted plasmonic nanocolumns of silver (Ag) on top fabricated by physical vapor deposition at large oblique angles on predefined gratings show unique plasmonic properties. These aligned nanocolumns with high-aspect ratios can be uniformly re-oriented to any desired angle of slant by ion beam irradiation. A focused ion beam (FIB) has been used… (More)

- Sangeeta Chakrabarti, Sri Ramakrishna, Sébastien Guenneau
- Optics express
- 2006

The electromagnetic properties of finite checkerboards consisting of alternating rectangular cells of positive refractive index (epsilon= +1, micro= +1) and negative refractive index (epsilon= -1, micro= -1) have been investigated numerically. We show that the numerical calculations have to be carried out with very fine discretization to accurately model… (More)

- Muamer Kadic, Sébastien Guenneau, Stefan Enoch, Sri Ramakrishna
- ACS nano
- 2011

We extend designs of perfect lenses to the focusing of surface plasmon polaritons (SPPs) propagating at the interface between two anisotropic media of opposite permittivity sign. We identify the role played by the components of anisotropic and heterogeneous tensors of permittivity and permeability, deduced from a coordinate transformation, in the dispersion… (More)