[17p-A402-1~18] 3.12 Nanoscale optical science and near-field optics

[17p-A402-14] Gradient Dielectric Metasurfaces: Wavefront Control by Non-discrete Phase Patterns

〇Masashi Miyata¹, Mitsumasa Nakajima¹, Toshikazu Hashimoto¹ (1.NTT Device Technology Labs)

Keywords:metasurface, grating, metamaterial

Optical wavefront manipulation by dielectric or plasmonic metasurfaces has been attained by tailoring metasurface building blocks in size and shape, and arranging them on a lattice to match a desired phase profile response. However, such metasurfaces inevitably generate a discrete multi-level phase profile due to the spacing of building blocks. This hinders the creation of high-performance metasurfaces, such as large-angle optical beam deflectors. Here, we demonstrate an approach based on continuous gradient metasurfaces (CGMs) capable of generating a non-discrete phase profile. The CGMs consist of amorphous-silicon (a-Si) nanobeams whose width is gradually modulated along their length. Since the phase value varies with nanobeam width, the CGMs enable spatially continuous phase modulation along the nanobeams and thereby provide the matching with a desired phase profile. We explore the validity of this concept in optical beam deflectors fabricated with a CGM.