  Polarizers are essential in diverse photonics applications including display
[1], microscopy [2], polarimetric astrophysical observation [3], laser
machining [4], and quantum information processing [5]. Whereas conventional
polarizers based on natural crystals and multilayer thin films are commonplace,
nanostructured polarizers offer compact integrability [6,7], thermal stability
in high-power systems [4,8], and space-variant vector beam generation [9,10].
Here, we introduce a new class of reflectors and polarizers fashioned with
dielectric nanowire grids that are mostly empty space. It is fundamentally
extremely significant that the wideband spectral expressions presented can be
generated in these minimal systems. We provide computed results predicting high
reflection and attendant polarization extinction in multiple spectral regions.
Experimental results with Si nanowire arrays show ~200-nm-wide band of total
reflection for one polarization state and free transmission for the orthogonal
state. These results agree quantitatively with theoretical predictions.
