Broadband Multifunctional Efficient Meta-Gratings
Based on Dielectric Waveguide Phase Shifters
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Abstract
Molding the wavefront of light is
a basic principle of any optical design. In conventional optical components
such as lenses and waveplates, the wavefront is controlled via propagation
phases in a medium much thicker than the wavelength. Metasurfaces
instead typically produce the required phase changes using subwavelength-sized
resonators as phase shift elements patterned across a surface. This
“flat optics” approach promises miniaturization and
improved performance. Here we introduce metasurfaces which use dielectric
ridge waveguides (DRWs) as phase shift elements in which the required
phase accumulation is achieved via propagation over a subwavelength
distance. By engineering the dispersive response of DRWs, we experimentally
realize high resolving power meta-gratings with broadband (λ
= 1.2–1.7 μm) and efficient routing (splitting and bending)
into a single diffraction order, thus overcoming the limits of blazed
gratings. In addition, we demonstrate polarization beam splitting
capabilities with large suppression ratios