The aim of an invisibility device is to guide light around any object put inside, being able to hide objects from sight. Here, we propose a novel design of dielectric invisibility device based on an optically isotropic material with negatively refracting index. Using an optical conformal mapping [1,2], we show that this device creates perfect invisibility. In particular, it represents an example of possible cloaking devices where the time delay is zero. Furthermore, due to impedance matching of negatively refracting materials, the waves are completely transmitted when crossing different material index borders, and consequently reflecting waves are also zero [3]. These findings strongly indicate that perfect invisibility with isotropic materials is possible.
Meta-materials are man-made media where electromagnetic waves do not behave as usually expected. This is also true for the recently discovered meta-materials with negative refractive index. A striking property of materials with negative index is that the rays will be refracted on the same side of the normal on entering the material according to the Snell’s law. Then, by taking advantage of this property, we design a novel cloaking device with two Riemann sheets. While the first Riemann sheet the material has refractive index n=1, the second Riemann sheet is composed of four quadrants with alternative values negative and positive refractive index profile n (see Fig.1). As a consequence, the existence of quadrants with different refractive index makes it possible to generate bounded orbits with more relaxing constrains than suggested previously [1, 2]. By using the negative refractive index, the trajectory around branch cut points in the second Rieman sheet can be seen as a mirror-like reflection of light.
Fig.1 Trajectory of light in the second Rieman sheet.
While previous cloaking devices were proposed using anisotropic materials [4,5], here we have designed a device using isotropic media, which seems easier to construct. From the theoretical side, our approach has also shown that it is possible in isotropic media to get around the formidable shape of the Nachman’s theorem [6]. In summary, our findings strongly indicate that perfect invisibility with isotropic materials is possible and opens new possibilities on the way to invisibility in the visible range of the spectrum.
[1] U. Leonhardt, New. J. Phys. 8, 118 (2006).
[2] U. Leonhardt, Science 312, 1777 (2006).
[3] T.Ochiai, U.Leonhardt and J.C. Nacher, J. Math. Physics, 49, 032903 (2008).
[4] J.B. Pendry, D.Schurig, D.R. Smith, Science 312, 1780 (2006).
[5] D. Schurig, et al, Science 314, 977 (2006).
[6] A. I. Nachman, Ann. Math. 128, 531 (1998).
Links Cloak of Invisibility, Metamaterials, Photonics and Perfect Lens
http://www.st-andrews.ac.uk/~ulf/ (Dr. Ulf Leonhardt)
http://www.cmth.ph.ic.ac.uk/photonics/ (Dr. Pendry)
http://people.engr.ncsu.edu/dschuri/ (Dr. Schurig)
http://www.ee.duke.edu/~drsmith/cloaking.html (Dr. Smith)
Past Conferences
The 50th International Conference on. Solid State Devices and Materials (SSDM 2008). Date : September 23-26, 2008
http://www.coin2008.ieice.org/
The 7th International Conference on Optical Internet. October 14-16, 2008. Akihabara, Tokyo, Japan
http://congress2008.metamorphose-vi.org/
2nd International Congress on Advanced Electromagnetic Materials in
Microwaves and Optics, Navarra, 9-12 September, 2008
6th International Conference on Photo-Excited Processes and Applications
9-12 Sep 2008, Sapporo, Hokkaido, Japan