OAM spatial demultiplexing by diffraction-based noiseless mode conversion with axicon

The physics of orbital angular momentum (OAM) carrying light has been well-defined since the 1990s. Leveraging its physical phenomena has become a significant focus in various areas of research. For instance, OAM is applied in hybrid free-space optical communication channels, like wavelength division multiplexing. Due to its orthogonality, OAM can be multiplexed and demultiplexed, enabling the use of multiple orthogonal OAM beams to achieve high-capacity optical communication systems. In this appliance, there will be instability of light because its phase distribution is quite complicated. This study focuses on spatial demultiplexing using Computer Generated Holography (CGH) based OAM diffraction. Earlier research on OAM diffraction primarily involved fork gratings. Spatial demultiplexing has phase distribution instability and noise problems in free space optics. Axicons have been studied extensively in the context of perfect vortex generation. Drawing inspiration from these two areas of physics, we propose a noiseless topological charge conversion through axicon properties in spatial demultiplexing using CGH. Furthermore, we estimate the axicon optical approximate solution that is appropriate for research purposes.