Light Transport and Vortex Formation in All Solid Band Gap Fibres

Study of optical vortices (OV) is a growing area of research bringing together advanced theoretical and mathematical concepts and emerging technologies [1]. The necessary condition of OV existence is zero amplitude on a certain line representing the vortex axis. The zero - amplitude line may coincide with the axis of light beam or have more complicated shape [2]. It is known that the most important feature of the optical vortex formation is the rotation of the Poynting vector (energy rotation) around the phase dislocation (the OV core) [1]. It should also be noted that when the zero amplitude line has the shape of a ring the phases of the plane wavefront inside the ring and outside it differ by π [2]. In this work, we examine the linear OVs that occur in the cladding of all-solid-band-gap fibres (ASBGFs) [3]. In the case of ASBGFs the formation of OVs can have strong impact on localization of the core modes. We demonstrate that the vortex formation in ASBGFs is determined by the location of the zero - amplitude lines in the cladding elements.