Shaping polarization within an ultrafast laser pulse using dielectric metasurfaces

Coherent light–matter interactions on the femtosecond time scale form the backbone of ultrafast science and technology, where the instantaneous state of light is used to control and detect the interaction of light with matter. Here, the polarization state of light has proven pivotal in unveiling intrinsic chiral or anisotropic optical response in various material systems, and it is critical for applications requiring complex polarization encoding including in spectroscopy, telecommunications, and coherent control. While wave plates in various forms play a crucial role in shaping the landscape of polarization management, engineering the instantaneous state of polarization within an ultrafast pulse for an arbitrary input-polarization remains challenging. Here, by leveraging the nanoscale multidimensional control of light offered by metasurfaces, we engineer the temporal evolution of the instantaneous polarization state of a femtosecond pulse through parallel manipulation of its constituent spectral components across an ultrawide bandwidth. We expect such control over the synthesis of complex vectorially shaped pulses to further elucidate ultrafast chiral light–matter interactions.