Ultrafast laser-driven topological phase patterning.

Microscopic and dynamic control over quantum states is essential for bridging fundamental studies of material properties to device function. Realizing such control at combined high spatial resolution and ultrafast temporal precision remains a major challenge. Here, we demonstrate femtosecond laser-driven patterning of topological quantum states in the Weyl semimetal WTe2. By engineering the excitation field into a transient optical grating, we create spatially selective and reversible structural distortions that induce local transitions between topological and topologically trivial states. Using ultrafast transmission electron microscopy, we directly visualize the formation of a periodic Td/1T* heterostructure, observe the propagation of a phase front, and analyze nanoscale confinement of coherently excited optical phonon modes. Our findings establish a platform for all-optical, spatially programmable, and reconfigurable control of quantum states, paving the way for optically addressable topological devices.