  Light carrying orbital angular momentum (OAM) holds unique properties and
boosts myriad applications in diverse fields from micro- to macro-world.
Endeavors have been made to manipulate the OAM in order to generate on-demand
structured light and to explore novel properties of light. However, the
generation of an ultrafast wave packet carrying numerous vortices with various
OAM modes, that is vortex string, has been rarely explored and remains a
significant challenge. Moreover, methods that enable parallel detection of all
vortices in a vortex string are lacking. Here, we demonstrate that a vortex
string with 28 spatiotemporal optical vortices (STOVs) can be successfully
generated in an ultrafast wave packet. All STOVs in the string can be randomly
or orderly arranged. The diffraction rules of STOV strings are also revealed
theoretically and experimentally. Following these rules, the topological
charges and positions of all STOVs in a vortex string can be easily recognized.
The strategy for parallel generation and detection of STOV strings will open up
exciting perspectives in STOV-based optical communications and also promote
promising applications of the structured light in light-matter interaction,
quantum information processing, etc.
