Optical Trapping Technology And Study On The Focusing Properties Of Annular Laser Beam

With the development of Laser Biography, the optical trapping technology based on microbeam laser becomes an effective tool in the research of life science and bioengineering little by little.Laser Trapping technology,called Optical Tweezers,is a primary application of laser radiation pressure.When a tight focused laser beam passes through a micro-particle,e.g. a cell or living biological specimens,the particle will be manipulated accurately without physics contact and invasion,due to the three-dimensional optical gradient force.Laser trapping is already widely used in physics,chemistry,medicine,biology,life science,materials science,and so on.In this thesis,the development of the optical tweezers and current investigation on this novel technology were summarized firstly,and the optical tweesers was explained in elementary theory,and the basic conception,such as laser radiation pressure, optical gradient force,optical scatter force,optical potential well,and so on,were explained in detail,and the condition of the optical trapping force constrainting the micro-particles was qualitative analysed.In the aspect of the quantitative calculation of optical trapping force,the calculation models were builded according to the contradistinction of the microsphere and the laser wavelength.Based on Ray-Optics Model, the optical trapping force is calculated quantitatively on the microsphere which is much bigger than the laser wavelength. By using Electromagnetic Model, the quantitative analysis is also presented, which is about the optical trapping force of Rayleigh particle much smaller than the laser wavelength.In the apparatus design aspect, at first we design an optical tweezers instrument with one optical trap,and introduce detailedly the selection rule of the every structure of the instrument,especially discuss the selection of the laser optical source and the microscope object lens. On this basis, then we discuss the other optical tweezers systems including Dual Optical Trap Tweezers, Hollow Laser Tweezers,Optic fiber Laser Tweezers,Calculation Holography Laser Tweezers.The focusing properties of annular laser beam based on the Hollow Laser Tweezers was discussed.The nonlinear propagation and focusing process of two dimensions annular super-Gaussian beam have been numerically simulated by using the split-step Fast Fourier-Bessel transform (SSFFT) methods and the intensity distribution in the vicinity of the focusing field of the annular beam has been gotten. The effects of the ratio of inner to outer radius of annular beam and nonlinear modulations on the annular beam focusing properties ,including center intensity of focal plane, the transverse distribution of the focal plane intensity, the intensity of optical axis and the beam quality, have been investigated.This paper is a preparatory job in terms of theory and technology for constructing an optical tweezers instrument. It is of importance reference value to optical tweezers research in instrument design and its wider application in life science and biography technology.