Fig. 2
From: Complex vectorial optics through gradient index lens cascades
VVBs generation through GRIN lens cascades. a (i) Schematic of a single GRIN lens cascade with (ii) right-hand circular input, output polarization fields for both simulation and experimental results (the red side of the colour scale indicates right-hand circular, whereas blue corresponds to left-hand circular). Note that before the GRIN lens cascade, there is a polarization state generator (PSG) to generate a chosen arbitrary polarization state; following the GRIN lens is a polarization state analyser (PSA) that enables Stokes vector measurement (see methods in Supplementary Note 3). Except in (iii) the PSG and PSA parts are omitted for clarity. (iii) An illustration for schematic in a with right-hand circular input and left hand circular analysis. The two spirals in the interferogram (iv) and the phase profile (v) indicated that the light beam contained two units of OAM. b–g show higher-order GRIN lens cascades and their generated light fields under specific inputs. In e–g the red-coloured GRIN lens indicate another GRIN type with a larger magnitude retardance profile almost equivalent to a sequence of three of the first (orange) type of lens (for details see Supplementary Note 4)
