Phase and amplitude gradient waveguide coupled metasurfaces

This paper presents a novel silicon-based metasurface-coated one-dimensional (1D) slab waveguide. The proposed idea can easily engineer and mold guided waves into any desired free-space mode and provide the wavefront control of optical metasurfaces, such as out-of-plane beam deflection and focusing. As an example of application and also in order to prove the functionality of the proposed method, we design such a metalens with a focal length of [Formula: see text] nm at 1550 nm. The final results show the electric field distribution at different heights above the waveguide with clear focusing which confirms our design concept. Also, intensity distribution at the focal plane exhibits significant improvement in focal spot size for final design with full width at half-maximum of about 893 nm. It can be found that all the analytical features of this metasurface can be fulfilled at arbitrary frequency-band. In addition, we investigate the beam squinting of the proposed structure at different wavelengths around 1550 nm. We found small beam squinting over the bandwidth. Therefore, the methodology of this paper can be used to reduce the beam squinting of metasurfaces. Actually, the desired main-beam squinting of the proposed metasurface could be obtained by engineering the parameters of the silicon-bars instead of changing the working wavelength. Guided wave driven property of this metasurface makes it a good candidate to integrate with on chip components. The design concept of this paper can be easily extended to any other optical applications in communications with full on-chip integration, such as solid-state LiDAR, remote sensing, displays, etc.