Ways to control and design topological features in various systems are being studied intensively because the resulting properties tend to be robust against things such as scattering and defects, endowing the system with topological protection. Maczewsky et al. now look to another regime in optics to show that optical nonlinearity can induce a topological change in the properties of a photonic lattice. At low excitation power, probe light uniformly leaks into the rest of the lattice, an optically trivial phase. Above a threshold power, optical nonlinearity induces a topological change in the properties of the photonic lattice, and probe light is confined to propagate along the edge of the structure. These results illustrate a route to dynamically control the propagation of light. Science , this issue p.  A hallmark feature of topological insulators is robust edge transport that is impervious to scattering at defects and lattice disorder. We demonstrate a topological system, using a photonic platform, in which the existence of the topological phase is brought about by optical nonlinearity. The lattice structure remains topologically trivial in the linear regime, but as the optical power is increased above a certain power threshold, the system is driven into the topologically nontrivial regime. This transition is marked by the transient emergence of a protected unidirectional transport channel along the edge of the structure. Our work studies topological properties of matter in the nonlinear regime, providing a possible route for the development of compact devices that harness topological features in an on-demand fashion. : /lookup/doi/10.1126/science.abd2033
People have been trying for a very long time to figure out the special fabric that might render people invisible. Researchers at Michigan Technological University hope that photonic crystals may be the answer, according to a new study in a special issue of Journal of Optics, reported Thursday by Science Daily. Most approaches tend to rely on manipulating electromagnetic waves and optics -- when it comes to invisibility cloaks, the idea is basically to find a way to get the waves to divert in an orderly way around an object -- but there are others who say moving to a digital approach may be the way to go. Take for instance optical physicist Joseph Choi, who told CNN that digitally manipulating the light is the best option and likely to be available much quicker.
Topological Materials Manmade photonic crystals offer a flexible platform for controlling the propagation and flow of light. Such control can be extended across the electromagnetic spectrum by correctly engineering the bandgap. Limitations in the fabrication process, however, can result in structural imperfections that allow the light or energy to leak out. Wang et al. add magnetism to the mix to form heterostructures of magnetic photonic crystals. They demonstrate that, for microwaves, this magnetic addition provides a topological aspect to the band structure, resulting in the propagation of the microwaves in one direction that is robust to defects. The ability to controllably route and collimate electromagnetic waves also could be applied to electronic and phononic waveguide systems. Phys. Rev. Lett. 126 , 067401 (2021).
Intel executive vice president Diane Bryant unveiled silicon photonics at the Intel Developer Forum in San Francisco on August 17, 2016. Intel on Tuesday announced it's launching silicon photonics, a product 16 years in the making, to enhance the use of optics for data center traffic management. It has a tremendous advantage over other silicon solutions, Intel executive vice president Diane Bryant said at the Intel Developer Forum in San Francisco. Intel is "the first to light up silicon," she said, integrating the laser light-emitting material onto silicon. It uses silicon lithography to align the laser with precision, she said, creating a cost advantage because it's automatically aligned.
The constructive and destructive interference of waves is often exploited in optics and signal transmission. The interference pattern is a direct measure of the phase difference between two or more beams. Such a phase difference may result from the difference between the optical paths traversed by the light beams. However, phase can change for a single beam if it propagates through an "anisotropic parameter space," a medium that curves the light; this property is called geometric or topological phase (1–4). On page 1202 of this issue, Maguid et al. (5) use metasurfaces--ultrathin, planar engineered structures (6–9)--to form shared-aperture antenna arrays that impart geometric phase to optical signals.