Laguerre-Gaussian beam transformations by the double-phase-ramp converter: Singular skeleton formation and its sensitivity to small misalignments

摘要

A double-phase-ramp (DPR) converter is known as an element introducing the screw dislocation into an input beam with smooth wavefront, or increasing (decreasing) the topological charge of the input beam with optical vortex (OV). We study the features of the set of phase singularities (singular skeleton, SS) formed within the Laguerre-Gaussian beam LG_0~4 after passage through the charge-lowering DPR converter. The main attention is paid to the SS sensitivity to small transverse misalignments in horizontal, vertical and diagonal directions of the DPR converter with respect to the nominal centered position. The obtained results are compared with the SS characteristics typical for the case of perfect DPR alignment. It is shown that different OVs in the transformed field have different misalignment sensitivity. Conditions enabling especially high sensitivity of the separate OVs are revealed and discussed.