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

Abstract: Coherent light with orbital angular momentum (OAM) is of great interest, and more 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 3rd harmonic of the Gaussian mode seed laser was discussed for the Shanghai deep ultraviolet free-electron laser (SDUV-FEL). The considerations on the experiment setup, the expected performance and the possible measurement method are given.