Feasibility study on optical vortex generation at Shanghai deep ultraviolet free-electron laser postprint

Abstract: Coherent light with orbital angular momentum (OAM) is of great interest. Recently, OAM light generation by coupling a relativistic electron beam with a Gaussian mode laser pulse at the high harmonics of a helical undulator has been demonstrated experimentally. In this paper, the possibility of delivering coherent OAM light at the 3^rd harmonic of the Gaussian mode seed laser is discussed for the Shanghai deep ultraviolet free-electron laser (SDUV-FEL). Considerations are given on the experiment setup, the expected performance and the possible measurement method.