Semiconductor nanowire metamaterial for broadband near-unity absorption.

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 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.

Tapered InP nanowire arrays for efficient broadband high-speed single-photon detection.

Superconducting nanowire single-photon detectors with peak efficiencies above 90% and unrivalled timing jitter (<30 ps) have emerged as a potent technology for quantum information and sensing applications. However, their high cost and cryogenic operation limit their widespread applicability. Here, we present an approach using tapered InP nanowire p-n junction arrays for high-efficiency, broadband and high-speed photodetection without the need for cryogenic cooling. The truncated conical nanowire shape enables a broadband, linear photoresponse in the ultraviolet to near-infrared range (~500 nm bandwidth) with external quantum efficiencies exceeding 85%. The devices exhibit a high gain beyond 105, such that a single photon per pulse can be distinguished from the dark noise, while simultaneously showing a fast pulse rise time (<1 ns) and excellent timing jitter (<20 ps). Such detectors open up new possibilities for applications in remote sensing, dose monitoring for cancer treatment, three-dimensional imaging and quantum communication.