Fig. 1: Illustration of an optical Archimedes’ screw.
a A mechanical Archimedes screw carries fluids from a lower to a higher ground56. b An optical screw is a medium whose permittivity and permeability tensors are modulated such that the principal axes \(\overrightarrow{\delta \varepsilon }\) and \(\overrightarrow{\delta \mu }\) of their modulation describe two helices. Furthermore, in our model we allow for a dephasing 2ϕ between the two modulations. For zero-dephasing (ϕ = 0), at θ = gx − Ωt = 0, \(\overrightarrow{\delta \varepsilon }\) points along the x-axis while \(\overrightarrow{\delta \mu }\) points along the y-axis. For finite dephasing ϕ ≠ 0 the two modulations are shifted forward and backward in space-time by 2ϕ, so that their total phase difference is 2ϕ.
