[Perspective] Photonic multitasking enabled with geometric phase



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. These devices can control photonic spin and enable multiple optical functions. Author: Natalia M. Litchinitser