The possibility of making an optically large (many wavelengths in diameter) object appear invisible has been a subject of many recent studies. Exact invisibility scenarios for large (relative to the wavelength) objects involve (meta)materials with superluminal phase velocity [refractive index (RI) less than unity] and/or magnetic response. We introduce a new approximation applicable to certain device geometries in the eikonal limit: piecewise-uniform scaling of the RI. This transformation preserves the ray trajectories but leads to a uniform phase delay. We show how to take advantage of phase delays to achieve a limited (directional and wavelength-dependent) form of invisibility that does not require loss-ridden (meta)materials with superluminal phase velocities.
© 2012 Optical Society of America
Original Manuscript: June 14, 2012
Revised Manuscript: August 16, 2012
Manuscript Accepted: September 17, 2012
Published: October 24, 2012
Yaroslav Urzhumov and David R. Smith, "Low-loss directional cloaks without superluminal velocity or magnetic response," Opt. Lett. 37, 4471-4473 (2012)