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Topological activity of layered chiral optical Bragg waveguides

We have shown that a layered chiral Bragg waveguide possesses topological activity in the bandgap spectral region. In this region the topological charge of the incoming optical field may be changed upon reflection by unity. We demonstrate numerically the generation of a narrow-band optical vortex from an incident Gaussian beam, as well as the generation of optical vortices with topological charge increased by unity from incident optical vortices. It is shown that such fibres can operate as reflective and transmitting converters of Hermite–Gaussian beams into optical vortices.