Very-Large-Scale-Integrated High-$Q$ Nanoantenna Pixels (VINPix)

TL;DR

This paper introduces VINPix, a high-$Q$, subwavelength nanoantenna array platform that achieves simultaneous high quality factors, dense integration, and controlled far-field radiation, enabling advanced optical devices.

Contribution

The authors design and demonstrate VINPix, a novel nanoantenna array that combines guided mode resonances with photonic crystal cavities to achieve high-$Q$, small mode volume, and high-density integration.

Findings

Achieved $Q$-factors exceeding 1500 with $V_m$ less than 0.1 $( ext{λ}/n_{ ext{air}})^3$.

Fabricated an 8 mm x 8 mm array with over a million nanoantennas per $ ext{cm}^2$.

Demonstrated a proof-of-concept refractive-index sensor using the VINPix array.

Abstract

Metasurfaces provide a versatile and compact approach to free-space optical manipulation and wavefront shaping. Comprised of arrays of judiciously-arranged dipolar resonators, metasurfaces precisely control the amplitude, polarization, and phase of light, with applications spanning imaging, sensing, modulation, and computing. Three crucial performance metrics of metasurfaces and their constituent resonators are the quality factor ($Q$-factor), mode-volume ($V_m$), and the ability to control far-field radiation. Often, resonators face a trade-off between these parameters: a reduction in $V_m$ leads to an equivalent reduction in $Q$, albeit with more control over radiation. Here, we demonstrate that this perceived compromise is not inevitable $-$ high-$Q$, subwavelength $V_m$, and controlled dipole-like radiation can be achieved, simultaneously. We design high-$Q$, very-large-scale integrated silicon nanoantenna pixels $-$ VINPix $-$ that combine guided mode resonance waveguides with photonic crystal cavities. With optimized nanoantennas, we achieve $Q$-factors exceeding 1500 with $V_m$ less than 0.1 $(\lambda/n_{\text{air}})^3$. Each nanoantenna is individually addressable by free-space light, and exhibits dipole-like scattering to the far-field. Resonator densities exceeding a million nanoantennas per $\text{cm}^2$ can be achieved, as demonstrated by our fabrication of an 8 mm x 8 mm VINPix array. As a proof-of-concept application, we demonstrate spectrometer-free, spatially localized, refractive-index sensing utilizing a VINPix array. Our platform provides a foundation for compact, densely multiplexed devices such as spatial light modulators, computational spectrometers, and in-situ environmental sensors.