A collaboration work between Austria, Germany, Canada and us, has now been published in Optica.
In the work, we show that one can convert circularly polarized, i.e. light with spin angular momentum, to orbital angular momentum carrying light fields with a surprisingly high conversion efficiency even if the interface planar and uniform. The conversion is naturally happening when light is focused quite tight while sent through the uniform interface, however, with a thin layer of a so-called epsilon-near-zero material the effect is massively enhanced.
In case you are interested to read more about the effect and see some beautiful experimental result, check it out here.