Measurement method for photon spin orbital angular momentum joint mode and measurement system

The invention discloses a measurement method for a photon spin-orbital angular momentum joint mode and a measurement system. The measurement method comprises the steps of vertically inputting a to-be-measured optical field with spin-orbital angular momentum into a plane (x, y), and enabling the center of the optical field to be aligned with the center of the plane; introducing phase modulation QL(x, y) into left-handed circular polarization state incident light with a spiral wavefront, and introducing phase modulation QR(x, y) into right-handed circular polarization state incident light with aspiral wavefront; enabling light fields with different spin angular momentum to be expanded along a spiral line and be separated to different positions on a plane (u, v); introducing a compensation phase PL(x, y) into the left-handed circular polarization incident light with the spiral wavefront, introducing a compensation phase PR(x, y) into the right-handed circular polarization incident lightwith the spiral wavefront, and converging the light fields passing through the plane (u, v) at different positions of the plane (m, n); and detecting light intensity distribution of the plane (m, n) to measure a spin-orbital angular momentum joint mode input into the light field or to demodulate the spin-orbital angular momentum joint mode input into the light field.