Intrinsic Orbital Angular Momentum Originated from Optical Catastrophe Superposition

TL;DR

This paper demonstrates that optical catastrophe beams inherently possess intrinsic orbital angular momentum (OAM) independent of phase vortices, challenging traditional associations and expanding understanding of OAM origins.

Contribution

It reveals that superimposed catastrophe beams exhibit intrinsic OAM without relying on phase vortex topological charge, supported by theoretical and experimental analysis.

Findings

CCBs rotate during autofocusing and particle manipulation.

OAM of CCBs can be tuned by changing superimposed beams.

OAM is intrinsic and not linked to phase vortex topological charge.

Abstract

Conventionally, intrinsic orbital angular momentum (OAM) is associated with phase vortices. However, our investigation into the propagation dynamics of 2D superimposed catastrophe beams, termed cyclone catastrophe beams (CCBs), reveals that these beams inherently exhibit rotation and possess OAM, distinct from the typical connection to phase vortices. Our observations clearly show these beams rotating during autofocusing propagation and particle manipulation, confirming the presence of OAM. Theoretical calculations affirm that the OAM of these beams is intrinsic and can be adjusted by varying the number of superimposed beams. Furthermore, our interference and phase studies indicate that, although CCBs exhibit phase vortices, they do not rotate around the singularities of phase vortices and their total topological charges are zero. This implies that the manifestation of OAM within CCBs does not rely on nonzero topological charge of the presented phase vortices within CCBs. Especially, eigenstates decomposition analysis illustrates that CCBs can be decomposed as a composite of Laguerre-Gaussian (LG) modes with uneven fidelity, where the topological charges of LG modes align with multiples of the superimposed catastrophe beams but do not equal to the value of the OAM per photon within CCBs, emphasizing the intrinsic OAM within CCBs and the absence of a connection to phase vortices. Our findings not only advance the understanding of the relationship between OAM and phase vortices but also pave the way for different applications of OAM waves, catalyzing their development in optics and other domains.