[1] Dorn R, Quabis S, Leuchs G. Sharper focus for a radially polarized light beam[J]. Physical Review Letters, 2003, 91(23): 233901.

[2] Lavery M P J, Speirits F C, Barnett S M, et al. . Detection of a spinning object using light's orbital angular momentum[J]. Science, 2013, 341(6145): 537-540.

[3] Vitullo D L P, Leary C C, Gregg P, et al. . Observation of interaction of spin and intrinsic orbital angular momentum of light[J]. Physical Review Letters, 2017, 118(8): 083601.

[4] Wiesbauer M, Wollhofen R, Vasic B, et al. Nano-anchors with single protein capacity produced with STED lithography[J]. Nano Letters, 2013, 13(11): 5672-5678.

[5] Padgett M, Bowman R. Tweezers with a twist[J]. Nature Photonics, 2011, 5(6): 343-348.

[6] Patchkovskii S, Spanner M. Nonlinear optics: high harmonics with a twist[J]. Nature Physics, 2012, 8(10): 707-708.

[7] Parigi V. D'Ambrosio V, Arnold C, et al. Storage and retrieval of vector beams of light in a multiple-degree-of-freedom quantum memory[J]. Nature Communications, 2015, 6: 7706.

[8] Willner A E, Huang H, Yan Y, et al. Optical communications using orbital angular momentum beams[J]. Advances in Optics and Photonics, 2015, 7(1): 66-106.

[9] Curtis J E, Grier D G. Structure of optical vortices[J]. Physical Review Letters, 2003, 90(13): 133901.

[10] Yan L, Gregg P, Karimi E, et al. Q-plate enabled spectrally diverse orbital-angular-momentum conversion for stimulated emission depletion microscopy[J]. Optica, 2015, 2(10): 900-903.

[11] Apurv Chaitanya N, Chaitanya Kumar S, Devi K, et al. Ultrafast optical vortex beam generation in the ultraviolet[J]. Optics Letters, 2016, 41(12): 2715-2718.

[12] Cai X, Wang J, Strain M J, et al. Integrated compact optical vortex beam emitters[J]. Science, 2012, 338(6105): 363-366.

[13] Yang Y M, Wang W Y, Moitra P, et al. Dielectric meta-reflectarray for broadband linear polarization conversion and optical vortex generation[J]. Nano Letters, 2014, 14(3): 1394-1399.

[14] Klauss A, Konig M, Hille C. Upgrade of a scanning confocal microscope to a single-beam path STED microscope[J]. PLoS ONE, 2015, 10(6): e0130717.

[15] Gregg P, Kristensen P, Ramachandran S. 13. 4 km OAM state propagation by recirculating fiber loop[J]. Optics Express, 2016, 24(17): 18938-18947.

[16] Berweger S, Atkin J M, Olmon R L, et al. Adiabatic tip-plasmon focusing for nano-Raman spectroscopy[J]. The Journal of Physical Chemistry Letters, 2010, 1(24): 3427-3432.

[17] Barthes J, des Francs G C, Bouhelier A, et al. . A coupled lossy local-mode theory description of a plasmonic tip[J]. New Journal of Physics, 2012, 14(8): 083041.

[18] Hayazawa N, Saito Y, Kawata S. Detection and characterization of longitudinal field for tip-enhanced Raman spectroscopy[J]. Applied Physics Letters, 2004, 85(25): 6239-6241.

[19] Bretschneider S, Eggeling C, Hell S W. Breaking the diffraction barrier in fluorescence microscopy by optical shelving[J]. Physical Review Letters, 2007, 98(21): 218103.

[20] Mino T, Saito Y, Yoshida H, et al. Molecular orientation analysis of organic thin films by z-polarization Raman microscope[J]. Journal of Raman Spectroscopy, 2012, 43(12): 2029-2034.

[21] Min C J, Shen Z, Shen J F, et al. Focused plasmonic trapping of metallic particles[J]. Nature Communications, 2013, 4: 2891.

[22] Saito Y, Verma P. Polarization-controlled Raman microscopy and nanoscopy[J]. The Journal of Physical Chemistry Letters, 2012, 3(10): 1295-1300.

[23] Ramachandran S, Kristensen P. Optical vortices in fiber[J]. Nanophotonics, 2013, 2(5/6): 455-474.

[24] Zhang W D, Huang L G, Wei K Y, et al. High-order optical vortex generation in a few-mode fiber via cascaded acoustically driven vector mode conversion[J]. Optics Letters, 2016, 41(21): 5082-5085.

[25] Grosjean T, Courjon D, Spajer M. An all-fiber device for generating radially and other polarized light beams[J]. Optics Communications, 2002, 203(1/2): 1-5.

[26] Ndagano B, Brüning R. McLaren M, et al. Fiber propagation of vector modes[J]. Optics Express, 2015, 23(13): 17330-17336.

[27] Gregg P, Kristensen P, Ramachandran S. Conservation of orbital angular momentum in air-core optical fibers[J]. Optica, 2015, 2(3): 267-270.

[28] Vengsarkar A M, Lemaire P J, Judkins J B, et al. Long-period fiber gratings as band-rejection filters[J]. Journal of Lightwave Technology, 1996, 14(1): 58-65.

[29] Ramachandran S, Kristensen P, Yan M F. Generation and propagation of radially polarized beams in optical fibers[J]. Optics Letters, 2009, 34(16): 2525-2527.

[30] Bozinovic N, Golowich S, Kristensen P, et al. Control of orbital angular momentum of light with optical fibers[J]. Optics Letters, 2012, 37(13): 2451-2453.

[31] Li S H, Mo Q, Hu X, et al. Controllable all-fiber orbital angular momentum mode converter[J]. Optics Letters, 2015, 40(18): 4376-4379.

[32] Zhang W D, Wei K Y, Huang L G, et al. Optical vortex generation with wavelength tunability based on an acoustically-induced fiber grating[J]. Optics Express, 2016, 24(17): 19278-19285.

[33] Zhang W D, Huang L G, Wei K Y, et al. Cylindrical vector beam generation in fiber with mode selectivity and wavelength tunability over broadband by acoustic flexural wave[J]. Optics Express, 2016, 24(10): 10376-10384.

[34] Zhang W D, Wei K Y, Mao D, et al. Generation of femtosecond optical vortex pulse in fiber based on an acoustically induced fiber grating[J]. Optics Letters, 2017, 42(3): 454-457.

[35] Zhang W D, Wei K Y, Wang H, et al. Tunable-wavelength picosecond vortex generation in fiber and its application in frequency-doubled vortex[J]. Journal of Optics, 2018, 20(1): 014004.

[36] Vayalamkuzhi P, Bhattacharya S, Eigenthaler U, et al. Direct patterning of vortex generators on a fiber tip using a focused ion beam[J]. Optics Letters, 2016, 41(10): 2133-2136.

[37] Ribeiro R S, Dahal P, Guerreiro A, et al. Optical fibers as beam shapers: from Gaussian beams to optical vortices[J]. Optics Letters, 2016, 41(10): 2137-2140.

[38] Weber K, Hütt F, Thiele S, et al. Single mode fiber based delivery of OAM light by 3D direct laser writing[J]. Optics Express, 2017, 25(17): 19672-19679.

[39] Alexeyev C N, Lapin B P, Milione G, et al. Publisher's note: optical activity in multihelicoidal optical fibers[J]. Physical Review A: Covering Atomic, Molecular, and Optical Physics and Quantum Information, 2015, 92(3): 039905.

[40] Fang L, Wang J. Flexible generation/conversion/exchange of fiber-guided orbital angular momentum modes using helical gratings[J]. Optics Letters, 2015, 40(17): 4010-4013.

[41] Xu H X, Yang L. Conversion of orbital angular momentum of light in chiral fiber gratings[J]. Optics Letters, 2013, 38(11): 1978-1980.

[42] Dashti P Z, Alhassen F, Lee H P. Observation of orbital angular momentum transfer between acoustic and optical vortices in optical fiber[J]. Physical Review Letters, 2006, 96(4): 043604.

[43] Dashti P Z, Li Q, Lin C H, et al. Coherent acousto-optic mode coupling in dispersion-compensating fiber by two acoustic gratings with orthogonal vibration directions[J]. Optics Letters, 2003, 28(16): 1403-1405.

[44] Wei K Y, Zhang W D, Huang L G, et al. Generation of cylindrical vector beams and optical vortex by two acoustically induced fiber gratings with orthogonal vibration directions[J]. Optics Express, 2017, 25(3): 2733-2741.

[45] Dong J L, Chiang K S. Temperature-insensitive mode converters with CO2-laser written long-period fiber gratings[J]. IEEE Photonics Technology Letters, 2015, 27(9): 1006-1009.

[46] Zhao Y H, Liu Y Q, Zhang L, et al. Mode converter based on the long-period fiber gratings written in the two-mode fiber[J]. Optics Express, 2016, 24(6): 6186-6195.

[47] Fu C L, Liu S, Wang Y, et al. High-order orbital angular momentum mode generator based on twisted photonic crystal fiber[J]. Optics Letters, 2018, 43(8): 1786-1789.

[48] Pidishety S, Srinivasan B, Brambilla G. All-fiber fused coupler for stable generation of radially and azimuthally polarized beams[J]. IEEE Photonics Technology Letters, 2017, 29(1): 31-34.

[49] Willig K I, Kellner R R, Medda R, et al. Nanoscale resolution in GFP-based microscopy[J]. Nature Methods, 2006, 3(9): 721-723.

[50] Schmidt R, Wurm C A, Jakobs S, et al. Spherical nanosized focal spot unravels the interior of cells[J]. Nature Methods, 2008, 5(6): 539-544.

[51] Willig K I, Rizzoli S O, Westphal V, et al. STED microscopy reveals that synaptotagmin remains clustered after synaptic vesicle exocytosis[J]. Nature, 2006, 440(7086): 935-939.

[52] Willig K I, Harke B, Medda R, et al. STED microscopy with continuous wave beams[J]. Nature Methods, 2007, 4(11): 915-918.

[53] YanL, AuksoriusE, BozinovicN, et al. Optical fiber vortices for STED nanoscopy[C]∥CLEO: Science and Innovations 2013. San Jose: OSA Technical Digest (online).2013: CTu3N. 2.

[54] Gu M, Kang H, Li X P. Breaking the diffraction-limited resolution barrier in fiber-optical two-photon fluorescence endoscopy by an azimuthally-polarized beam[J]. Scientific Reports, 2014, 4: 3627.

[55] Bozinovic N, Yue Y, Ren Y, et al. Terabit-scale orbital angular momentum mode division multiplexing in fibers[J]. Science, 2013, 340(6140): 1545-1548.

[56] Li S H, Wang J. Multi-orbital-angular-momentum multi-ring fiber for high-density space-division multiplexing[J]. IEEE Photonics Journal, 2013, 5(5): 7101007.

[57] Li J P, Zhang J B, Li F, et al. DD-OFDM transmission over few-mode fiber based on direct vector mode multiplexing[J]. Optics Express, 2018, 26(14): 18749-18757.

[58] Stockle R M, Suh Y D, Deckert V, et al. Nanoscale chemical analysis by tip-enhanced Raman spectroscopy[J]. Chemical Physics Letters, 2000, 318(1/2/3): 131-136.

[59] Stadler J, Schmid T, Zenobi R. Nanoscale chemical imaging using top-illumination tip-enhanced Raman spectroscopy[J]. Nano Letters, 2010, 10(11): 4514-4520.

[60] Wang R, Wang J, Hao F H, et al. Tip-enhanced Raman spectroscopy with silver-coated optical fiber probe in reflection mode for investigating multiwall carbon nanotubes[J]. Applied Optics, 2010, 49(10): 1845-1848.

[61] Okuno Y, Saito Y, Kawata S, et al. Tip-enhanced Raman investigation of extremely localized semiconductor-to-metal transition of a carbon nanotube[J]. Physical Review Letters, 2013, 111(21): 216101.

[62] Kravtsov V, Ulbricht R, Atkin J M, et al. Plasmonic nanofocused four-wave mixing for femtosecond near-field imaging[J]. Nature Nanotechnology, 2016, 11(5): 459-464.

[63] Müller M, Kravtsov V, Paarmann A, et al. Nanofocused plasmon-driven sub-10 fs electron point source[J]. ACS Photonics, 2016, 3(4): 611-619.

[64] Berweger S, Atkin J M, Xu X G, et al. Femtosecond nanofocusing with full optical waveform control[J]. Nano Letters, 2011, 11(10): 4309-4313.

[65] Umakoshi T, Saito Y, Verma P. Highly efficient plasmonic tip design for plasmon nanofocusing in near-field optical microscopy[J]. Nanoscale, 2016, 8(10): 5634-5640.

[66] Tugchin B N, Janunts N, Klein A E, et al. Plasmonic tip based on excitation of radially polarized conical surface plasmon polariton for detecting longitudinal and transversal fields[J]. ACS Photonics, 2015, 2(10): 1468-1475.

[67] Ramachandran S, Smith C, Kristensen P, et al. Nonlinear generation of broadband polarisation vortices[J]. Optics Express, 2010, 18(22): 23212-23217.