A novel phase-only modulated method allowing generation of multichannel orbital angular momentum (OAM) based on helical long-period fiber grating (HLPG) has been proposed. Thanks to the method of a phase-only modulation, the proposed HLPG does not need a complex apodization in the grating’s profile, which considerably facilitates the fabrication processes and makes the designed multichannel OAM generator particularly suitable for fabrication with using the CO2 laser-writing platform. As one typical example, the phase-only modulated 3-channel OAM generator has been demonstrated both theoretically and experimentally. This is the first report for generation of a multi-channel (wavelength) OAM mode by using only one HLPG.
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