Generalized spiral transformation for high-resolution sorting of vortex modes

We achieve high-resolution sorting of the orbital angular momentum (OAM) of light with two bespoke diffractive optical elements using the generalized spiral transformation. The experimental sorting finesse is 5.3, approximately two times better performance than what has been reported. These optical elements will be useful for optical communication based on OAM beams and can be easily extended to other fields that use conformal mapping.