Generation and regulation of coaxial composite vortex beams based on liquid crystal devices

Traditional multi-vortex beams are mostly off-axis,which limit their applications due to the need for more precise lenses,complex optical paths,and poor imaging quality. In this paper,a mixed q-plate based on liquid crystal devices is designed and fabricated. The transmittance of q-plate is greater than 95% and the coaxial composite vortex beam can be generated. The propagation characteristics of the composite vortex beams generated by this device are theoretically and experimentally demonstrated. The beam exhibits novel diffraction phenomena such as spin and long-distance self-healing after diffraction. The generation of coaxial composite vortex beams avoids the disadvantages of off- axis traditional multi- vortex beams. This research provides a new method for particle capture and manipulation,optical information processing, optical encryption and optical measurement.