Sub-picosecond steering of ultrafast incoherent emission from semiconductor metasurfaces

The ability to dynamically steer sub-picosecond pulses from a monolithically integrated source is a critical milestone for the fields of nanophotonics and ultrafast optics. Reconfigurable dielectric metasurfaces have demonstrated the potential to exert dynamic control over the properties of light at sub-wavelength scales using spatial phase engineering. However, active manipulation of incoherent light sources remains a challenge, as current phase-sensitive metasurfaces developed for coherent sources cannot be directly applied. Here we theoretically predict and experimentally demonstrate sub-picosecond steering of ultrafast incoherent emission from a light-emitting metasurface over a 70° range. We utilize a monolithic III–V (GaAs) metasurface with embedded (InAs quantum dot) light sources positioned on a reflective Bragg (AlAs/Al 0.3 Ga 0.7 As) mirror to achieve a large optically induced phase change near the emission wavelength (1.25 μm). We use a spatial light modulator to structure a strong optical pump (800 nm) and project it onto the resonant metasurface to create reconfigurable spatial momentum profiles that dynamically steer the ultrafast (140 fs) quantum dot emission. Such dynamic spatiotemporal control of incoherent sources can enable new technologies for high-speed communications, holography and remote sensing.