RESUMO
Dielectric metasurfaces built up with nanostructures of high refractive index represent a powerful platform for highly efficient flat optical devices due to their easy-tuning electromagnetic scattering properties and relatively high transmission efficiencies. Here we show visible-frequency silicon metasurfaces formed by three kinds of nanoblocks multiplexed in a subwavelength unit to constitute a metamolecule, which are capable of wavefront manipulation for red, green, and blue light simultaneously. Full phase control is achieved for each wavelength by independently changing the in-plane orientations of the corresponding nanoblocks to induce the required geometric phases. Achromatic and highly dispersive meta-holograms are fabricated to demonstrate the wavefront manipulation with high resolution. This technique could be viable for various practical holographic applications and flat achromatic devices.
RESUMO
Dielectric metasurfaces are capable of completely manipulating the phase, amplitude, and polarization of light with high spatial resolutions. The emerging design based on high-index and low-loss dielectrics has led to the realization of novel metasurfaces with high transmissions, but these devices usually operate at the limited bandwidth, and are sensitive to the incident polarization. Here, we report the realization of the polarization-independent and high-efficiency silicon metasurfaces spanning the visible wavelengths about 200 nm. The fabricated computer-generated meta-holograms exhibit a 90% diffraction efficiency, which are verified by gradient metasurfaces with measured efficiencies up to 93% at 670 nm, and exceeding 75% at the wavelengths from 600 to 800 nm for the two orthogonally polarized incidences. These dielectric metasurfaces effectively decouple the phase modulation from the polarization states and frequencies for visible light, which hold great potential for novel flat optical devices operating over a broad spectrum.
