[1] 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).
[2] BETH R A. Mechanical detection and measurement of the angular momentum of light[J]. Physical Review, 50, 115-125(1936).
[3] SIMPSON N B, DHOLAKIA K, ALLEN L, et al. Mechanical equivalence of spin and orbital angular momentum of light: an optical spanner[J]. Optics Letters, 22, 52-54(1997).
[4] YAO A M, PADGETT M J. Orbital angular momentum: origins, behavior and applications[J]. Advances in Optics and Photonics, 3, 161-204(2011).
[5] MAIR A, VAZIRI A, WEIHS G, et al. Entanglement of the orbital angular momentum states of photons[J]. Nature, 412, 313-316(2001).
[6] UCHIDA M, TONOMURA A. Generation of electron beams carrying orbital angular momentum[J]. Nature, 464, 737-739(2010).
[7] WANG J, YANG J Y, FAZAL I M, et al. Terabit free-space data transmission employing orbital angular momentum multiplexing[J]. Nature Photonics, 6, 488-496(2012).
[8] BOZINOVIC N, YUE Y, REN Y X, et al. Terabit-scale orbital angular momentum mode division multiplexing in fibers[J]. Science, 340, 1545-1548(2013).
[9] BLIOKH K Y, NORI F. Spatiotemporal vortex beams and angular momentum[J]. Physical Review A, 86, 033824(2012).
[10] JHAJJ N, LARKIN I, ROSENTHAL E W, et al. Spatiotemporal optical vortices[J]. Physical Review X, 6, 031037(2016).
[11] HANCOCK S W, ZAHEDPOUR S, GOFFIN A, et al. Free-space propagation of spatiotemporal optical vortices[J]. Optica, 6, 1547-1553(2019).
[12] CHONG A, WAN C H, CHEN J, et al. Generation of spatiotemporal optical vortices with controllable transverse orbital angular momentum[J]. Nature Photonics, 14, 350-354(2020).
[13] CHEN J, WAN C H, CHONG A, et al. Subwavelength focusing of a spatio-temporal wave packet with transverse orbital angular momentum[J]. Optics Express, 28, 18472-18478(2020).
[14] 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).
[15] WOLF E. Electromagnetic diffraction in optical systems. I. An integral representation of the image field[J]. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 253, 349-357(1959).
[16] RICHARDS B, WOLF E. Electromagnetic diffraction in optical systems. II. Structure of the image field in an aplanatic system[J]. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 253, 358-379(1959).
[17] HELSETH L E. Focusing of atoms with strongly confined light potentials[J]. Optics Communications, 212, 343-352(2002).
[18] HELSETH L E. Optical vortices in focal regions[J]. Optics Communications, 229, 85-91(2004).