Relativistic laser pulse has been used as an important research tool in well known high energy density physics as well as in ultrahigh momentum density which has many important applications like radiation pressure acceleration. But another important character of relativistic laser, orbital angular momentum ( OAM) effect was ignored.

In the paper “Light Fan Driven by a Relativistic Laser Pulse”[Phys.Rev.Lett.112, 235001(2014)http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.112.235001] by State Key Laboratory of High Field Laser Physics which was published in Physical Review Letters, a “light fan” scheme was proposed to study the OAM effect. In this scheme, a relativistic laser pulse (with a very high photon density) impinges on a spiral-shaped foil (the fan). It shows that the fan achieves a large OAM and the reflected pulse is transformed into Laguerre-Gaussian (LG ) mode with large opposite OAM.

As the referee said that it is “the first time that a method has been proposed to extend this to pulses at relativistic intensity levels”, the study opens a new research field, high OAM density physics. It may bring new perspective of research as well as potential applications. 

State Key Laboratory of High Field Laser Physics are cooperating with the team led by Prof. Changhe Zhou of Laboratory of Information Optics and Optoelectronic Technology, to produce specially designed deep-etched grating, aiming to transform a fs PW laser pulse to LG mode.  

This work was supported by the National Basic Research Program of China (973 Program) and the National Natural Science Foundation of China.