20 research outputs found
Direct, stigmatic, imaging with curved surfaces
We study the possibilities of direct (using one intersection with each light ray) stigmatic imaging with a curved surface that can change ray directions in an arbitrary way. By purely geometric arguments we show that the only possible case of such imaging is the trivial one where the image of any point is identical to the point itself and the surface does not perform any change of the ray direction at all. We also discuss an example of a curved surface which performs indirect stigmatic imaging after twice intersecting each light ray
Dr TIM: Ray-tracer TIM, with additional specialist scientific capabilities
We describe several extensions to TIM, a raytracing program for ray-optics
research. These include relativistic raytracing; simulation of the external
appearance of Eaton lenses, Luneburg lenses and generalized focusing
gradient-index (GGRIN) lenses, which are types of perfect imaging devices;
raytracing through interfaces between spaces with different optical metrics;
and refraction with generalised confocal lenslet arrays, which are particularly
versatile METATOYs.Comment: 12 pages, 16 figure
Invisibility cloaking without superluminal propagation
Conventional cloaking based on Euclidean transformation optics requires that
the speed of light should tend to infinity on the inner surface of the cloak.
Non-Euclidean cloaking still needed media with superluminal propagation. Here
we show by giving an example that this is no longer necessary
Efficient sharing of a continuous-variable quantum secret
We propose an efficient scheme for sharing a continuous variable quantum
secret using passive optical interferometry and squeezers: this efficiency is
achieved by showing that a maximum of two squeezers is required to replicate
the secret state, and we obtain the cheapest configuration in terms of total
squeezing cost. Squeezing is a cost for the dealer of the secret as well as for
the receivers, and we quantify limitations to the fidelity of the replicated
secret state in terms of the squeezing employed by the dealer.Comment: 7 pages, 3 figure
Non-Euclidean cloaking for light waves
Non-Euclidean geometry combined with transformation optics has recently led
to the proposal of an invisibility cloak that avoids optical singularities and
therefore can work, in principle, in a broad band of the spectrum [U. Leonhardt
and T. Tyc, Science 323, 110 (2009)]. Such a cloak is perfect in the limit of
geometrical optics, but not in wave optics. Here we analyze, both analytically
and numerically, full wave propagation in non-Euclidean cloaking. We show that
the cloaking device performs remarkably well even in a regime beyond
geometrical optics where the device is comparable in size with the wavelength.
In particular, the cloak is nearly perfect for a spectrum of frequencies that
are related to spherical harmonics. We also show that for increasing wavenumber
the device works increasingly better, approaching perfect behavior in the limit
of geometrical optics
An omnidirectional retroreflector based on the transmutation of dielectric singularities
In the field of transformation optics, metamaterials mimic the effect of
coordinate transformations on electromagnetic waves, creating the illusion that
the waves are propagating through a virtual space. Transforming space by
appropriately designed materials makes devices possible that have been deemed
impossible. In particular, transformation optics has led to the demonstration
of invisibility cloaking for microwaves, surface plasmons and infrared light.
Here we report the achievement of another "impossible task". We implement, for
microwaves, a device that would normally require a dielectric singularity, an
infinity in the refractive index. We transmute a singularity in virtual space
into a mere topological defect in a real metamaterial. In particular, we
demonstrate an omnidirectional retroreflector, a device for faithfully
reflecting images and for creating high visibility, from all directions. Our
method is robust, potentially broadband and similar techniques could be applied
for visible light