Molecular Alignment Echo for Controlling the Readout Time of Vortex Beams.

We present an experimental study of molecular alignment echoes driven by ultrashort structured light fields carrying orbital angular momentum (OAM). By combining two time-delayed pump pulses with spatially varying polarization, we produce a molecular "q plate" in a gaseous CO_{2} sample that can be rephased in a controllable manner. This approach enables the storage of OAM information within the rotational coherences of molecules and its retrieval at adjustable times. The concept is validated using vortex beams of various topological charges ℓ=±1, 2. These results extend the mechanism of molecular alignment echoes to vector light fields and establish a new route for optical processing of ultrashort OAM pulses, advancing molecular-based quantum interfaces for structured light.