Full-wafer fabrication of all-inorganic metalenses, waveguides and diffractive optics via nanoimprint lithography

We fabricate all-inorganic, high refractive index optics, including metalenses, waveguides, and diffractive optical elements via nanoimprint lithography with TiO2 nanoparticle dispersion inks and report full-wafer, high-throughput fabrication of waveguides and visible wavelength metalenses lenses with absolute efficiencies greater than 75% (>90% of design efficiency). We employ atomic layer deposition (ALD) as a post-imprint treatment that enables tuning of the refractive index from 1.9 to 2.25 using less than 20 cycles, which improves lens efficiency. Tuning RI of the imprinted optics to match that of the substrates removes concerns about residual layer thickness, resolving a critical issue for some applications. Additional cycles of ALD enable precise tuning of feature dimensions and feature spacings. Finally, we demonstrate the excellent optical and material stabilities of the all-inorganic imprinted optics.