Pragmatic Metasurface Hologram at Visible Wavelength: The Balance between Diffraction Efficiency and Fabrication Compatibility

Metasurfaces have shown many interesting physical phenomena by designing the subwavelength antennas and, thus, controlling the complex amplitude of optical waves. Practicality is one of the biggest challenges of metasurfaces because practical applications have not been realized yet, despite well-demonstrated metasurfaces such as achromatic lenses, holograms, and optical cloaks. Early metasurfaces composed of plasmonic resonators have a significant loss of optical power at visible wavelengths. Amorphous silicon, which is easy to fabricate, can overcome the optical loss only above the wavelength of 600 nm. Use of other dielectric materials such as crystalline silicon or titanium dioxide drastically increases the efficiency of the metasurfaces at whole visible wavelengths, but complex fabrication processes remain an ongoing challenge for practical applications. Here, we exploit polycrystalline silicon to achieve both fabrication compatibility and hologram functionality at the wavelength of 532 nm. Polarization-independent meta hologram is experimentally demonstrated to verify our approach, and our device shows the highest efficiency compared to other reported meta holograms that do not need complicated fabrication processes. We believe that our approach can provide a useful perspective on practicality improvement of metasurfaces.