Search

Controlling the direction of light emission on the subwavelength scale is a key capability for quantum information processing and optical imaging in photonics and biology1–5. The spin–orbit interaction of light is widely adopted for dynamically tuning the direction of circularly polarized photoluminescence (PL), but this is challenging to accomplish for many luminescence materials, which typically generate unpolarized luminescence. Here, we report optical control of unidirectional emission of unpolarized luminescence in a spatially symmetric nanopillar lattice assisted by photonic orbital angular momenta. The orientation of anti-Stokes shift PL emissions can be controlled by the helicity of incident vortex beams. The experimental directionality of unpolarized PL emission in the one-dimensional nanopillar lattice can reach 0.59, which is markedly stronger than that possible by a spin mechanism. Our findings thus offer a new promising approach for tuneable nanoscale optical control of emission. The use of a nanopillar lattice and orbital angular momentum provides control over the directionality of light emission on the nanoscale. [ABSTRACT FROM AUTHOR]

Reconfigurable optical metasurfaces are rapidly emerging as a major frontier in photonics research, development and commercialization. They promise compact, lightweight and energy-efficient reconfigurable optical systems with unprecedented performance and functions that can be dynamically defined on-demand. Compared with their passive counterparts, the reconfiguration capacity also poses challenges in scalable control, manufacturing and control toward their practical deployment. This Review aims to survey the state of the art of reconfigurable metasurface technologies and their applications, using spaceborne remote sensing, active beam steering and light field displays as examples, while highlighting key research advances that are essential to enabling their transition from laboratory curiosity to commercial reality. Recent developments in reconfigurable metasurfaces are reviewed with a focus on case studies that are promising for commercialization and associated challenges. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (TMDCs) present extraordinary nonlinearities and direct bandgaps at the K and K′ valleys. These valleys can be optically manipulated through, for example, plasmon–valley-exciton coupling with spin-dependent photoluminescence. However, the weak coherence between the pumping and emission makes exploring nonlinear valleytronic devices based on TMDCs challenging. Here, we show that a synthetic metasurface, which entangles the phase and spin of light, can simultaneously enhance and manipulate nonlinear valley-locked chiral emission in monolayer tungsten disulfide (WS2) at room temperature. The second-harmonic valley photons, accessed and coherently pumped by light, with a spin-related geometric phase imparted by a gold (Au) metasurface, are separated and routed to predetermined directions in free space. In addition, the nonlinear photons with the same spin as the incident light are steered owing to the critical spin–valley-locked nonlinear selection rule of WS2 in our designed metasurface. Our synthetic TMDC–metasurface interface may facilitate advanced room-temperature and free-space nonlinear, quantum and valleytronic nanodevices. By entangling the phase and spin of light, a synthetic metasurface is shown to be able to coherently manipulate the valley-exciton-locked chiral emission in monolayer tungsten disulfide at room temperature. The findings will be of benefit to advanced room-temperature and free-space nonlinear, quantum and valleytronic nanodevices. [ABSTRACT FROM AUTHOR]

Light is a powerful tool to manipulate matter, but existing approaches often necessitate focused, high-intensity light that limits the manipulated object's shape, material and size. Here, we report that self-stabilizing optical manipulation of macroscopic—millimetre-, centimetre- and even metre-scale—objects could be achieved by controlling the anisotropy of light scattering along the object's surface. In a scalable design that features silicon resonators on silica substrate, we identify nanophotonic structures that can self-stabilize when rotated and/or translated relative to the optical axis. Nanoscale control of scattering across a large area creates restoring behaviour by engineering the scattered phase, without needing to focus incident light or excessively constrain the shape, size or material composition of the object. Our findings may lead to platforms for manipulating macroscopic objects, with applications ranging from contactless wafer-scale fabrication and assembly, to trajectory control for ultra-light spacecraft and even laser-propelled light sails for space exploration. Mechanical stability of macroscopic structures on the millimetre-, centimetre- and even metre-scale could be realized by tailoring the anisotropy of light scattering along the object's surface, without needing to focus incident light or excessively constrain the shape, size or material composition of the object. [ABSTRACT FROM AUTHOR]

Controlling light emission from quantum emitters has important applications, ranging from solid-state lighting and displays to nanoscale single-photon sources. Optical antennas have emerged as promising tools to achieve such control right at the location of the emitter, without the need for bulky, external optics. Semiconductor nanoantennas are particularly practical for this purpose because simple geometries such as wires and spheres support multiple, degenerate optical resonances. Here, we start by modifying Mie scattering theory developed for plane wave illumination to describe scattering of dipole emission. We then use this theory and experiments to demonstrate several pathways to achieve control over the directionality, polarization state and spectral emission that rely on a coherent coupling of an emitting dipole to optical resonances of a silicon nanowire. A forward-to-backward ratio of 20 was demonstrated for the electric dipole emission at 680 nm from a monolayer MoS2 by optically coupling it to a silicon nanowire. Based on a modified Mie scattering theory, several pathways to achieve control over the directionality, polarization state and spectral emission that rely on a coherent coupling of an emitting dipole in monolayer MoS2 to optical resonances of a silicon nanowire are reported. [ABSTRACT FROM AUTHOR]