The Charateristics Of The Superposition Of Laguere-gaussian Beams

Laguerre-Gaussian(LG)beams are widely used iin orbital angular momentum(OAM)multiplex communication systems,but there are currently limited to have a research only for zero-order radial LG beams(radial index p is zero).Compared with zero-order radial LG beams,high-order radial LG beams with radial index p also can be applied to OAM multiplexed communication systems,which can double channel capacity,communication rate and frequency band efficiency.Under the limitation of the receiving aperture,higher-order radial LG beams have more receiver power than the zero-order radial LG beams.Therefore,high-order radial LG beams have potential applications in OAM multiplexed communication systems.The study of the superposition of high-order radial LG beams can provide theoretical and experimental basis for solving the problem of orbital angular momentum detection in the future.In this paper,we mainly studied the generation of LG beams and its superposition state,the characteristics of the intensity distribution and the free space propagation characteristics.The main work is as follows:1.A liquid crystal spatial light modulator combined with a computational holography method is used to generate LG beams and their superposition states.Meanwhile,an optical system is created to generate LG beams and their superposition states.2.According to the principle of interference superposition,a new type of high-order composite vortex beam with a "petal" shape is generated by high-order radial LG beams with different topological charge.3.The superposition of zero-order radial LG beams and the superposition of high-order radial LG beams are studied.The effects of beam parameters such as topological charge,radial index and waist radius on the intensity distribution of composite vortex beam are discussed.The propagation properties of the superposition of zero-order radial LG beams and the superposition of the high-order radial LG beams in free space are studied.The research and analysis show that:(1)When high-order radial LG beams are coaxially superposed,if their topological charges are different greatly,a multi-annular composite vortex beam will be formed;if their topological charges are different slightly,a multi-layer "petal"composite vortex beam will be formed.(2)When the higher-order radial LG beams with opposite topological charges are coaxially superposed,a multi-layer bright "petal"-shaped composite vortex beam is formed.If the waist radius of the superimposed beams are different,the intensity distribution of composite vortex beam will rotate with the spinning "tailing"phenomenon.(3)High-order radial LG beams have a wide variety of composite vortex beams formed by coaxial superposition.When they propagate in free space,they will occur diffraction broadening.However,whether or not angular rotation occurs depends on whether there is extra phase in the superposition state.