Abstract: A polarization-insensitive device includes a liquid crystal layer and an adjustment layer that are stacked. The liquid crystal layer is configured to perform, under action of an electric field, first phase adjustment on a passing light component in a first polarization direction. The adjustment layer is configured to obtain a first light beam and a second light beam based on the incident light component in the first polarization direction that passes through the liquid crystal layer, second phase adjustment and polarization direction adjustment are performed on the first light beam at the adjustment layer. A polarization direction of the first light beam is perpendicular to a polarization direction of the first light beam obtained before the polarization direction adjustment; and the first light beam and the second light beam have different propagation directions after passing through the liquid crystal layer.

Abstract: The invention discloses a method and system for measuring orbital angular momentum modes of photons based on spiral transformation. A phase plate located in an input plane transforms the incident beam along a spiral path in the input plane into a straight line in an output plane and a phase plate located in the output plane compensate the phase accumulated when the beam propagates from the input plane to the output plane during the above transformation process, thereby realizing that the orbital angular momentum modes of photons to be measured in the input plane are transformed into plane wave modes with specific tilted wavefronts in the output plane. The plane wave modes with different tilted wavefronts can be focused on different positions on the focal plane and thus realize one-to-one mapping and detection between orbital angular momentum modes of photons and spatial locations.

Abstract: The invention discloses a method and system for measuring orbital angular momentum modes of photons based on spiral transformation. A phase plate located in an input plane transforms the incident beam along a spiral path in the input plane into a straight line in an output plane and a phase plate located in the output plane compensate the phase accumulated when the beam propagates from the input plane to the output plane during the above transformation process, thereby realizing that the orbital angular momentum modes of photons to be measured in the input plane are transformed into plane wave modes with specific tilted wavefronts in the output plane. The plane wave modes with different tilted wavefronts can be focused on different positions on the focal plane and thus realize one-to-one mapping and detection between orbital angular momentum modes of photons and spatial locations.