  The realization of a semiconductor near-unity absorber in the infrared will
provide new capabilities to transform applications in sensing, health, imaging,
and quantum information science, especially where portability is required.
Typically, commercially available portable single-photon detectors in the
infrared are made from bulk semiconductors and have efficiencies well below
unity. Here, we design a novel semiconductor nanowire metamaterial, and show
that by carefully arranging an InGaAs nanowire array and by controlling their
shape, we demonstrate near-unity absorption efficiency at room temperature. We
experimentally show an average measured efficiency of 93% (simulated average
efficiency of 97%) over an unprecedented wavelength range from 900 nm to 1500
nm. We further show that the near-unity absorption results from the collective
response of the nanowire metamaterial, originating from both coupling into
leaky resonant waveguide and transverse modes. These coupling mechanisms cause
light to be absorbed directly from the top and indirectly as light scatters
from one nanowire to neighbouring ones. This work leads to the possible
development of a new generation of quantum detectors with unprecedented
broadband near-unity absorption in the infrared, while operating near room
temperature for a wider range of applications.
