  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.
