  Phase-preserved optical elevator is an optical device to lift up an entire
plane virtually without distortion in light path or phase. Using transformation
optics, we have predicted and observed the realization of such a broadband
phase-preserved optical elevator, made of a natural homogeneous birefringent
crystal without resorting to absorptive and narrowband metamaterials involving
time-consuming nano-fabrication. In our demonstration, the optical elevator is
designed to lift a sheet upwards, and the phase is verified to be preserved
always. The camouflage capability is also demonstrated in the presence of
adjacent objects of the same scale at will. The elevating device functions in
different surrounding media over the wavelength range of 400-700 nm. Our work
opens up prospects for studies of light trapping, solar energy, illusion
optics, communication, and imaging.
