Disclosed are an orbital angular momentum generating apparatus and method for polarization modulation of orbital angular momentum. The generating apparatus comprises a Gaussian light source module, a first orbital angular momentum modulation module, a second orbital angular momentum modulation module and a multiplexing module, wherein when the apparatus works, the Gaussian light source module generates a Gaussian beam in any polarization state, and the Gaussian beam enters the multiplexing module, the multiplexing module decomposes the Gaussian beam into two polarization components each with a horizontal polarization direction and a vertical polarization direction, and the two polarization components are respectively imported into the first or second orbital angular momentum modulation module, the modulation module carries out polarization-independent orbital angular momentum modulation on the two components, and the two modulated light components are returned to the multiplexing module, and the multiplexing module optically superposes the two components, and finally outputs an orbital angular momentum state or a superposition state. The orbital angular momentum generating apparatus is compact in structure, and relatively low in manufacturing cost; devices and technology required by the apparatus are relatively mature; the orbital angular momentum state and the superposition state with any topological charge can be generated at a high speed; and the rate can reach the magnitude of MHz.
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