Design Of Self-Accelerating Beams And Applications In Optical Trapping

With self-bending,non-diffracting and self-healing dynamic properties,selfaccelerating beams,such as Airy beam,have attracted much attention in many fields.The realization and application of self-accelerating beams with different trajectories is a key topic in optics and related research fields.Here,the main challenge lies in the acquirement of non-paraxial self-accelerating beams of complex trajectories.Additionally,tractor beams propagation along a straight line inducing particles moving toward the light source has not only extended the application of optical tweezers,but also become a new focus in optical trapping due to its opposite direction to the light pressure.Nevertheless,self-accelerating beams acting on particles towards light source with a bending trajectory remain to be unequivocally determined.In this work,the main purpose is to understand and acquire the non-paraxial self-accelerating beams of complex trajectories,and make a negative traction on particles along a bending trajectory.The specific research mainly contains following parts:1)Theory of self-accelerating beams and optical trappingFirstly,we deduced the related theory of typical Airy beams under paraxial approximation and non-paraxial self-accelerating beams.Then,the basic principle of optical tweezers was described with several theoretical methods to calculate the optical trapping force exerted on the particles by the beams.Next,with diffraction angular spectrum theory,we explained the main mechanism to produce novel selfaccelerating beams.The most importantly,the work laid a solid foundation for the acquirement of self-accelerating beams of complex trajectories,and the realization of particles along bending trajectories in positive transports and negative tractions.2)Angular spectrum adjusted self-accelerating beamsBased on the research of angular spectrum on self-accelerating beams,we provided the specific method of adjusting angular spectrum to acquire non-paraxial self-accelerating beams of complex trajectories.With angular spectrum expansion of half-Bessel self-accelerating beams and Weber beams,we realized theoretically the periodic beam of the same trajectory but with intensity of secondary distribution,and also S-shape self-accelerating beams.The angular spectrum expansions of these beams were deduced as well.We calculated optical field distribution and Poynting vector of our self-accelerating beams,analysed and optimized the regulation methods and the control parameters.3)Particles transporting and negative dragging along beam trajectory with Self-accelerating beamsUsing Maxwell stress tensor and the law of conservation of momentum of electromagnetic field,we calculated the optical force exerted on the particles by the half-Bessel self-accelerating beams and S-shape beams in different directions.At the condition of equilibrium lateral force,we investigated the relationship between optical pulling force and the refractive index,sizes of the particles.Moreover,the other parameters and the relatively stable position of particles with known part of the parameters are analysed for the situation of optical pulling.We also provided the scattered fields of particles in negative traction and positive transport,specifically,and gave a physical explain behind the traction and transport phenomenon.Our work proposes new ideas and novel research methods to the study of selfaccelerating beams and its application research.It provide theoretical and methodological guidance to the optical manipulating under complex condition,meanwhile,a new application prospect of optical tweezers technology will also be explored.The results of this study are of great scientific significance and practical value for the development of Optics and related applications in other fields.