Patterning planar photo-absorbing materials into arrays of nanowires is demonstrated as a method for increasing the total photon absorption in a given thickness of absorbing material. Such a method can provide faster, cheaper, and more efficient photo-detectors and solar cells. A thin nanowire can absorb many more photons than expected from the size of the nanowire. The reason for this effect is that such nanowires support cylindrical particle resonances which can collect photons from an area larger than the physical cross-section of the wire. These resonances are sometimes referred to as Mie resonances or Leaky Mode Resonances (LMRs). The nanowires can have various cross section shapes, such as square, circle, rectangle, triangle, etc.