Generation of transverse light spring

We propose a scheme for generating a new type of spatiotemporally coupled twisted pulse, termed as a transverse light spring (LS). The most prominent feature of these light beams is the helical structure of the intensity contour in the transverse direction. This implies that the transverse light spring beam propagates forward, and the position of the high-intensity bright spot rotates in the transverse direction of its propagation. It is determined that this new pulse can be generated by superimposing multiple spatiotemporal vortex lights with different initial phases, which is verified via a theoretical analysis and particle-in-cell (PIC) simulation. A space-time beam with a spring structure perpendicular to its propagation direction can enable a host of novel applications.