Opt. Express 21, 1344–1352 (2013)

Transmission of light through, or reflection from, subwavelength arrays of metallic resonators has received renewed attention with several studies showing the possibilities for wavefront engineering and beam steering. A similar trick has long been used to great effect in the radiofrequency and microwave ranges. However, it is well known that metallic resonators and metamaterials can result in large losses for optical waves. Now, Longfang Zou and colleagues from the University of Adelaide and RMIT University in Australia propose a low-loss solution based on what they call dielectric resonator arrays. The resonators are designed to operate in the visible range and consist of small cylinders of TiO2 on silver substrates. The researchers claim that much of the optical energy in the resonator is stored in the dielectric part, and hence loss in the metal is reduced. The designed non-uniform planar array elements impart desired phase shifts across the wavefront, allowing the angle of reflection to be varied. The team created linear six-element sub-arrays on a 40 × 40 μm2 surface containing 126 × 126 resonator elements that efficiently deflected an optical beam with a wavelength of 633 nm.