Theoretical Research On Mechanical Properties Of Vortex Beams

In the 21st century,with the progress of light engineering technology,optics has ushered in a new revolution.At present,the vortex beams constructed based on light engineering technology has shown great application value in spiral phase contrast imaging,nonlinear optics,optical communication,quantum information,and optical micromanipulation.The application of vortex beams in optical micro-manipulation is mainly manifested in its mechanical properties.On the one hand,optical tweezers using vortex beams as incident light can reduce the thermal radiation to samples,which greatly enhances its application value.On the other hand,it can use the angular momentum of photons to drive the rotation of the trapped particles.At present,the optical micromanipulation technology with the vortex beams as the core has been widely used in biomedicine,colloid science,and optical drive.Therefore,it is particularly important to carry out research on the mechanical properties of the vortex beams.The theory of studying the mechanical effect of light on particles can be divided into two types:one is the geometric optical model,which is mainly for Mie particles whose size is much larger than the wavelength,and the other is the electromagnetic model,which is mainly used to analyze the Rayleigh particles whose size is much smaller than the wavelength.There have been many works studying the motion of Mie particles in the integer order vortex beams,but no work has been done to study the movement of Mie particles in the non-integer order vortex beams.In addition,the current research on the force of Rayleigh particles mainly focuses on the gradient force and the scattering force,and it is less concerned with the effect of the curl force on the Rayleigh particles.In view of the above problems,the first work of this paper mainly studies the angular motion of Mie particles under special vortex beams.We start from changing the energy flow density of vortex beams near the focal plane,two special vortex beams,the square vortex and the gamma vortex,are constructed.Taking the distribution of the energy flux density of the field near the focal point as the core,we discussed the influence of the square vortex and gamma vortex on the Mie particle,and predicted the possible motion of the particle.The second work of this paper mainly analyzes the effect of the vector vortex beams on the Rayleigh particle through the electromagnetic model.In this work,we consider the gradient force,scattering force and curl force of the light field on the axial direction of the Rayleigh particle,and compare the difference of the axial binding and orbital moment of Rayleigh particles under the radially polarized Laguerre-Gaussian field and the angularly polarized Laguerre-Gaussian field.We have concluded that the radially polarized Laguerre-Gaussian light field has more excellent effects in the above two aspects.