High Quality Factor Dielectric Metasurfaces for Two-Dimensional Wavefront Manipulation in Transmission

The strong interaction of light with optical nanostructures plays a critical role in optical sensing, nonlinear optics, and active optical devices. However, for wavefront shaping, the required local, sub-wavelength control over the phase of light limits this interaction, leading to low-quality-factor optical devices. Here, we report on high quality factor dielectric metasurfaces for complete, local wavefront manipulation of near infrared light in transmission mode, and in two dimensions. Our structure consists of high-index dielectric nanoparticles exhibiting strong, lattice-coupled Mie resonances with high quality factors. The local control of these resonances enables setting the phase of transmitted light over a range of 0-2π with experimentally measured quality factors of up to 295 at a wavelength of λ = 1290 nm. By appropriately tailoring the dimensions of these dielectric building blocks to attain the desired phase distribution, we experimentally realize wavelength-selective beam deflectors and radial metalenses with a bandwidth of only a few nanometers. Furthermore, we demonstrate the operation under finite illumination apertures (< 50 μm) and oblique incident illumination. This contrasts with other mechanisms for high-quality-factor optical metasurfaces which rely on inherently non-local principles, such as guided mode resonances or symmetry-breaking bound states in the continuum, limiting their application to one-dimensional wavefront shaping or geometric phase tuning, respectively. Our findings demonstrate that local control over the wavefront is successfully attained with high quality factor, opening doors to new applications in active metasurfaces and sensitive, free-space-coupled optical sensing.