Sub picosecond steering of ultrafast incoherent emission from semiconductor metasurfaces

The ability to dynamically steer fs pulses from a monolithically integrated source is a critical milestone for the fields of nanophotonics and ultrafast optics. The nascent field of reconfigurable metasurfaces -- made of optically resonant meta-atoms -- has shown great promise in manipulating light-matter interactions through subwavelength control of the phase, amplitude, and polarization of light. These active metasurfaces arbitrarily transform an incident wavefront using a reconfigurable spatial phase profile and thus have been limited to manipulating coherent external sources. Light emitting metasurfaces obtained through integration of incoherent emitters with meta-atoms, have been used to statically increase the quantum efficiency of the emission through Purcell factor enhancement and control the far-field emission properties of the light to collimate and focus spontaneous emission. Active manipulation of such incoherent light sources, however, remains a challenge as current phase-sensitive approaches used for coherent sources cannot be directly applied. Spatiotemporal control at ultrafast timescales of incoherent light emission could lead to a transformative technological leap allowing low-power light emitting diodes (LEDs) to replace high-power coherent laser sources, enabling holographic LED displays and other key optical transceiver applications including remote-sensing, perception, and high-speed optical communication systems. In this work, we theoretically predict and experimentally demonstrate for the first time, sub-picosecond steering over a 70{\deg} range of ultrafast incoherent emission from a light emitting metasurface.