[1] Huang Zhirong, Kim K J. Review of X-ray free-electron laser theory[J]. Physical Review Accelerators and Beams, 10, 034801(2007).
[2] Saldin E L, Schneidmiller E A, Yurkov M V. Statistical properties of radiation from VUV and X-ray free electron laser[J]. Optics Communications, 148, 383-403(1998).
[3] Stupakov G. Using the beam-echo effect for generation of short-wavelength radiation[J]. Physical Review Letters, 102, 074801(2009).
[4] Yu L H. Generation of intense uv radiation by subharmonically seeded single-pass free-electron lasers[J]. Physical Review A, 44, 5178-5193(1991).
[5] Feng Chao, Deng Haixiao, Zhang Meng, et al. Coherent extreme ultraviolet free-electron laser with echo-enabled harmonic generation[J]. Physical Review Accelerators and Beams, 22, 050703(2019).
[6] Ribič P R, Abrami A, Badano L, et al. Coherent soft X-ray pulses from an echo-enabled harmonic generation free-electron laser[J]. Nature Photonics, 13, 555-561(2019).
[7] Allen L, Beijersbergen M W, Spreeuw R J C, et al. Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes[J]. Physical Review A, 45, 8185-8189(1992).
[8] Franke‐Arnold S, Allen L, Padgett M. Advances in optical angular momentum[J]. Laser & Photonics Reviews, 2, 299-313(2008).
[9] Kuga T, Torii Y, Shiokawa N, et al. Novel optical trap of atoms with a doughnut beam[J]. Physical Review Letters, 78, 4713-4716(1997).
[10] Jack B, Leach J, Romero J, et al. Holographic ghost imaging and the violation of a Bell inequality[J]. Physical Review Letters, 103, 083602(2009).
[11] Shigematsu K, Yamane K, Morita R, et al. Coherent dynamics of exciton orbital angular momentum transferred by optical vortex pulses[J]. Physical Review B, 93, 045205(2016).
[12] Liu Baiyang, Cui Yuehui, Li Ronglin. A broadband dual-polarized dual-OAM-mode antenna array for OAM communication[J]. IEEE Antennas and Wireless Propagation Letters, 16, 744-747(2014).
[13] van Veenendaal M. Interaction between X-ray and magnetic vortices[J]. Physical Review B, 92, 245116(2015).
[14] Jüstel D, Friesecke G, James R D. Bragg–von Laue diffraction generalized to twisted X-rays[J]. Acta Crystallographica Section A:Foundations and Advances, 72, 190-196(2016).
[15] van Veenendaal M, McNulty I. Prediction of strong dichroism induced by X rays carrying orbital momentum[J]. Physical Review Letters, 98, 157401(2007).
[16] Ye L, Rouxel J R, Asban S, et al. Probing molecular chirality by orbital-angular-momentum-carrying X-ray pulses[J]. Journal of Chemical Theory and Computation, 15, 4180-4186(2019).
[17] Kotlyar V V, Almazov A A, Khonina S N, et al. Generation of phase singularity through diffracting a plane or Gaussian beam by a spiral phase plate[J]. Journal of the Optical Society of America A, 22, 849-861(2005).
[18] Beijersbergen M W, Allen L, Van der Veen H E L O, et al. Astigmatic laser mode converters and transfer of orbital angular momentum[J]. Optics Communications, 96, 123-132(1993).
[19] Terhalle B, Langner A, Päivänranta B, et al. Generation of extreme ultraviolet vortex beams using computer generated holograms[J]. Optics Letters, 36, 4143-4145(2011).
[20] Sasaki S, McNulty I, Dejus R. Undulator radiation carrying spin and orbital angular momentum[J]. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 582, 43-46(2007).
[21] Ribič P R, Gauthier D, De Ninno G. Generation of coherent extreme-ultraviolet radiation carrying orbital angular momentum[J]. Physical Review Letters, 112, 203602(2014).
[22] Hemsing E, Marinelli A. Echo-enabled X-ray vortex generation[J]. Physical Review Letters, 109, 224801(2012).
[23] Zhao Zhentang, Wang Dong, Gu Qiang, et al. Status of the SXFEL facility[J]. Applied Sciences, 7, 607(2017).
[24] Reiche S. GENESIS 1.3: a fully 3D time-dependent FEL simulation code[J]. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 429, 243-248(1999).