LASER & PHOTONICS REVIEWS Laser Photonics Rev. 9, No. 4, 412–418 (2015) / DOI 10.1002/lpor.201500041 ORIGINAL PAPER Abstract Recently, metasurfaces have received increasing attention due to their ability to locally manipulate the amplitude, phase and polarization of light with high spatial resolution. Transmissive metasurfaces based on high-index dielectric ma- terials are particularly interesting due to the low intrinsic losses and compatibility with standard industrial processes. Here, it is demonstrated numerically and experimentally that a uniform ar- ray of silicon nanodisks can exhibit close-to-unity transmission at resonance in the visible spectrum. A single-layer gradient metasurface utilizing this concept is shown to achieve around 45% transmission into the desired order. These values rep- resent an improvement over existing state-of-the-art, and are the result of simultaneous excitation and mutual interference of magnetic and electric-dipole resonances in the nanodisks, which enables directional forward scattering with a broad band- width. Due to CMOS compatibility and the relative ease of fabrication, this approach is promising for creation of novel flat optical devices. High-transmission dielectric metasurface with 2π phase control at visible wavelengths Ye Feng Yu *, ** , Alexander Y. Zhu , ** , Ram ´ on Paniagua-Dom´ ınguez, Yuan Hsing Fu, Boris Luk’yanchuk, and Arseniy I. Kuznetsov * 1. Introduction Recent years have witnessed significant research work in the area of optical metamaterials, broadly defined as arti- ficially synthesized media engineered at a size scale much smaller than the wavelength of incident light. In contrast to conventional materials whose intrinsic properties are fixed, metamaterials open up the exciting possibility of tailoring material properties to a specific application. Consequently numerous functionalities and devices have been developed, such as negative refractive index lenses, optical cloaking devices, artificial magnets, nanolasers, spasers and more [1]. Metasurfaces [2], which can be understood as a two- dimensional version of metamaterials, have garnered par- ticular attention due to their advantages of possessing a smaller physical footprint, simpler fabrication and lower losses compared to their bulk counterparts. Crucially, they retain the ability to manipulate the phase, amplitude and polarization of light upon transmission or reflection. Due to their two-dimensional nature, it is therefore possible to Data Storage Institute, A*STAR (Agency for Science, Technology and Research), 5 Engineering Drive 1, 117608,Singapore ∗∗ Equal contribution ∗ Corresponding authors: e-mails: yu_yefeng@dsi.a-star.edu.sg, arseniy_k@dsi.a-star.edu.sg realize planar analogs of traditional optical components, such as lenses, beam transformers, broadband pass filters, wave plates and polarization converters [2–4]. In addition, new functionalities arising from phase discontinuities at an interface can also be obtained, such as beam deflection [5–7], beam forming [8–12], and holography [13–15]. Plasmonic-based metasurfaces achieve the required full 2π phase control primarily using two different approaches. The first approach relies on the generation of two resonances, which can be independently tuned, each covering a standard phase range of π . For example, V-shaped antennas with different arm lengths and angles can generate symmetric and asymmetric modes. Full wavefront control can be achieved by varying the geometry of the antennas, which also takes into account material dispersion effects [6, 12]. The second approach is based on rotationally asymmetric nanostructures whose resonant modes are polarization dependent. Complete phase control can be achieved by spatially varying the geometric orientation of the nanostructures, due to phase singularity via the Pancharatnam–Berry phase [16]. However, the C  2015 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim