Fig. 6: Tunable emissions of OAM beams.

This is achieved by electrically tuning the phase mismatch quantity in a c-cut electro-optic lithium niobate crystal. a, b The voltage-dependent Rabi oscillatory modes achieved with an initial state \((\theta =\pi /2,\varphi =\pi /2)\) and a beam width r₀ = 4 μm: a, V = ±50 V (\(\triangle \beta =\mp 40.4{{\mathbf{m}}}^{{-}1}\)); b, V = ±200 V (\(\triangle \beta =\mp 161{{\rm{m}}}^{{-}1}\)). c, The motion trajectory (blue line) of the spinor, which moves slowly from point A to its initial position \((\theta =\pi /2,\varphi =\pi /2)\) by gradually sweeping the voltage from 0 to 1000 V; while altering the voltage sign producing a symmetric trajectory (purple line). d The same as described in c but in the case of r₀ = 5 μm. e, f The topological charge as a function of voltage after a coupling length z = 30 mm: e r₀ = 4 μm; f r₀ = 5 μm. The blue curves denote theoretical results, while the black data points indicate experiments. g The measured interferograms show a transition of the topological structure of light near V = 350 V, as highlighted by an ellipse in e