The quest for nanoscale light sources with designer radiation patterns and polarization has motivated the development of nanoantennas that interact strongly with the incoming light and are able to transform its frequency, radiation and polarization patterns. Here, we demonstrate dielectric AlGaAs nanoantennas for efficient second harmonic generation, enabling the control of both directionality and polarization of 1

In this work we demonstrate single axial p-i-n junction InP nanowire (NW) solar cells grown by selective-area metal organic vapor phase epitaxy (SA-MOVPE) technique. A power conversion efficiency of up to 6.5% was realized in the single NW solar cell (horizontally lying on substrate) without any surface passivation. Electron beam induced current (EBIC) and photocurrent mapping were performed to investigate the electrical properties of the NW solar cells and their influence on device performance, which are essential for an in-depth understanding of the design requirements for NW solar cells. A further conformal SiNx layer was deposited on the single NW solar cell devices by plasma-enhanced chemical vapor deposition (PECVD). Overall efficiency improvement has been obtained in the SiNx-coated devices with a remarkable up to 62% increase to a peak efficiency of 10.5%, which to our knowledge is the highest efficiency reported for horizontal single NW solar cells. This has been

Second-harmonic generation (SHG) in resonant dielectric Mie-scattering nanoparticles has been hailed as a powerful platform for nonlinear light sources. While bulk-SHG is suppressed in elemental semiconductors, e.g. silicon and germanium due to their centrosymmetry, the group of zincblende III-V compound semiconductors, especially (100)-grown AlGaAs and GaAs, have recently been presented as promising alternatives. However, major obstacles to push the technology towards practical applications are the limited control over directionality of the SH emission and especially zero forward/backward radiation, resulting from the peculiar nature of the second-order nonlinear susceptibility of this otherwise highly promising group of semiconductors. Furthermore, the generated SH signal for (100)-GaAs nanoparticles depends strongly on the polarization of the pump. In this work we provide both theoretically and experimentally a solution to these problems by presenting the first SHG nanoantennas made from ( 111)-GaAs embedded in a low index material. These nanoantennas show superior forward directionality compared to their (100)-counterparts. Most importantly, based on the special symmetry of the crystalline structure, it is possible to manipulate the SHG radiation pattern of the nanoantennas by changing the pump polarization without affecting the linear properties and the total nonlinear conversion efficiency, hence paving the way for efficient and flexible nonlinear beam shaping devices.

Nonlinear frequency conversion is one of the most fundamental processes in nonlinear optics. It has a wide range of applications in our daily lives, including novel light sources, sensing, and information processing. It is usually assumed that nonlinear frequency conversion requires large crystals that gradually accumulate a strong effect. However, the large size of nonlinear crystals is not compatible with the miniaturisation of modern photonic and optoelectronic systems. Therefore, shrinking the nonlinear structures down to the nanoscale, while keeping favourable conversion efficiencies, is of great importance for future photonics applications. In the last decade, researchers have studied the strategies for enhancing the nonlinear efficiencies at the nanoscale, e.g. by employing different nonlinear materials, resonant couplings and hybridization techniques. In this paper, we provide a compact review of the nanomaterials-based efforts, ranging from metal to dielectric and semiconductor nanostructures, including their relevant nanofabrication techniques.