Study Of Radiation Forces Of Focused Beams On Rayleigh Spherical Particles

Optical tweezers are a technology that uses optical traps to capture and manipulate particles based on laser technology and optical pressure theory.Compared with other technologies,optical tweezers technology has become one of the main means for scientists to effectively manipulate a single biological macromolecule because of its irreplaceable advantages.With the continuous innovation of science and technology,the traditional single-Gaussian optical tweezers can not meet the needs of scientists.New optical tweezers have attracted many scholars'research.These optical tweezers have better performance than single-Gaussian optical tweezers.Therefore,it is very important to investigate the radiation forces of the focused laser beams on the particle.In this paper,based on the generalized Huygens Fresnel principle and Rayleigh scattering theory,focused beams used to trap Rayleigh dielectric spheres with different refractive indices are studied,whose major contents are as follows:The analytical expressions of the radiation intensity and the radiation force on Rayleigh particles of a focused Hermite-Gaussian beams have been derived,This paper mainly focuses on the capture of two kinds of particles with different refractive index,as well as the effect of the beam order of m and n on the capture effect of the focused Hermite-Gaussian beams.The study found that the focused Hermite-Gaussian beam in the focal plane showing a rectangular array distribution?m+1?×?n+1?bright spot,the selection of suitable beam order can be achieved in the light spot array distribution capture?m+1?×?n+1?high refractive index of particles,while in the dark area capture m×?n+1?low refractive index particles.In addition,the larger the beam order,the greater the radiation force,the two types of Rayleigh particles can be captured more easily.Using the extended Huygens-Fresnel principle and Rayleigh scattering regime,the analytical expressions for the intensity and radiation forces of a focused Si G beam have been derived and used to study the optical trapping effect of focused Si G beams acting on dielectric sphere with different refractive indices.The results show that the focused Si G beams are distributed axisymmetrically along the?_r-axis,the central intensity of the two focal spots is the largest.The radiant force force of refraction particles at the maximum intensity increase with increasing the sin part associated parameter?₀.Therefore,the larger the values of ₀?,the easier it is to trap refraction particles at the maximum intensity.But the radiant force force of refraction particles at the maximum detensity decrease with increasing the focal length f.It can be used to trap high index of refraction particles at the sites of maximum intensity of the focal plane,and simultaneously two-dimensional plane?x-y plane?capture low index of refraction particles at the focus by selecting appropriate the sin part associated parameter ₀?and focal length f.Such focused Si G beams may have potential applications in nanotechnology and biotechnology.The optical trapping effect of coherent and incoherent superpositions of radial Gaussian beam array acting on a dielectric sphere are analyzed by using the Rayleigh scattering theory.It is found that both coherent and incoherent superimposed radial Gaussian beams array can capture high refractive index of particles in three dimensions on the focal plane.Furthermore,in the focal plane,the central intensity of coherent and incoherent superimposed radial Gaussian beams array is the largest.With the increase of the number of beamlets M,the intensity distribution of coherent superimposed Gaussian beams array increases exponentially,while the maximum intensity of incoherent superimposed Gaussian beams array increases geometrically.The radiant force force of refraction particles at the maximum intensity increase with the more the number of beamlets,the easier it is to capture the particle.