中文摘要：

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 3rdharmonic of the Gaussian mode seed laser is discussed for the Shanghai deep ultraviolet freeelectron laser（SDUV-FEL）.Considerations are given on the experiment setup,the expected performance and the possible measurement method.

英文摘要：

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 3rd 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.