Vortex Array Beam And Fabrication Of Chirped Grating

Optical vortex has special phase distribution,spiral wavefront and carries orbital angular momentum.Which makes it widely used in many fields such as optical micromanipulation and optical communication.Vortex array refers to the special vortex structure formed by multiple vortex beams in different arrangements.The vortex array can provide various functional optical traps with multiple phase singularities.Which not only enhance the information transmission capacity,but also increase the number of particles captured and observed in optical tweezers.Vortex beams applied to optical tweezers not only improve the efficiency of particle capture,but also carry orbital angular momentum that can be transferred to the absorbent particle and driving the particle to rotate.which is used in many fields such as biomedical engineering,material science and atomic physics.Chirped grating refers to grating whose period is not uniform.Chirped Bragg grating has high frequency response and strong dispersion,which has a broad application prospect in the fields of ultrashort pulse compression and broadening.The main research work of this thesis is as follows:1.Multiple single vortex beams generate multiple vortex array light fields in different arrangements.Which are distributed in linear structure,rectangular structure and radial structure.The structure of the vortex array,the number of array elements,the distance ang angle between adjacent vortex beams,the coordinate position and the topological charge of each vortex beams,which are flexibly designed according to the requirements of the experiment.The vortex array was made by experiment.And the experimental equipment is simple and easy to operate.2.Six beam plane waves on the same circle are symmetrically distributed,and the initial phase constitutes a complete vortex phase.With different topological charges of vortex phase,six beam planar phase interference generates many kinds of two-dimensional periodic array optical fields.The two-dimension array light field interfered with the plane wave along the z axis at the center of the circle,resulting in various three-dimension array light fields.The topological charge is 0 to generate a hexagonal three-dimension vortex array light field.The topological charge is 1 to generate a vortex three-dimension vortex array light field.The topological charge is 2 to generate a kagome three-dimension vortex array light field.The topological charge is 3 to generate a honeycomb three-dimension array light field.Hexagonal and honeycomb three-dimension array light fields have high intensity light surrounding the hollow beam,and vortex three-dimension light fields is intensive vortex array light field,both of which can be used for multi-optical trap control technology.3.Using vortex wave plate and holography to generate vortex beams and apply them to optical tweezers,Vortex beam is focused by a high-power objective lens to capture the SiO₂ particles in a ring optical trap.The orbital angular momentum carried by the photon is transferred to the particle,which is driven to rotate in a circular orbit.4.Laser beam focused by the cylindrical lens and incident on the LiNbO₃:Fe crystal.Observe the scattered light when the strip beam of o-light and e-light incident crystal.The periodic uneven grating generated in the crystal is called the chirped grating.The chirped Bragg grating is an axially symmetric chirped grating which is filled with the whole crystal.