  Invisibility or cloaking has captured human's imagination for many years.
With the recent advancement of metamaterials, several theoretical proposals
show cloaking of objects is possible, however, so far there is a lack of an
experimental demonstration at optical frequencies. Here, we report the first
experimental realization of a dielectric optical cloak. The cloak is designed
using quasi-conformal mapping to conceal an object that is placed under a
curved reflecting surface which imitates the reflection of a flat surface. Our
cloak consists only of isotropic dielectric materials which enables broadband
and low-loss invisibility at a wavelength range of 1400-1800 nm.
