Three-dimensional polarization-independent visible-frequency carpet invisibility cloak

We miniaturize all features in a previously introduced polarization-independent three-dimensional carpet invisibility cloak by more than a factor of 2. This leads to operation wavelengths in the visible. The structures are characterized by electron and optical microscopy. In contrast to our previous work at IR wavelengths, we can directly measure two-dimensional images at visible frequencies, perform control experiments from the back-side, and compare the images with theory. We find excellent agreement. Furthermore, we study the wavelength dependence in the range from 900nm down to 500nm. Cloaking action deteriorates as the woodpile stop band at around 575nm is approached. © 2011 Optical Society of America OCIS codes: 230.3205, 160.3918, 080.2710, 160.1245, 160.5298. Transformation optics can be viewed as a powerful tool for designing optical systems. The strength of this tool is emphasized by invisibility cloaking [1–3], which was long believed to be impossible. In particular, the carpet-cloak concept [4] has inspired experiments by several groups [5–13]. In brief, by tailoring a refractive-index profile, the carpet cloak makes a bump in a metal mirror (the carpet