Research Of Theory On Medium-Sized Particles Based On Optical Tweezer

The optical tweezers technology is based on microbeam laser,and began to study in the 20th century. The gradient force formed by a strongly focused laser beam can capture the dielectric neutral particles on its focus point, the size of the particles ranges from nm toμm. Optical tweezers can be used to manipulate biological animate specimens without physical contact. It has now become one of the research hot spot of new method and new instrument in biophysics.In this thesis, analysis of optical trapping force is given.Starting from a Debye-type integral representation valid for a laser beam focused through a high numerical aperture objective,we derive an explicit partial-wave representation for the force exerted on a dielectric sphere,and present comparisons with results.Firstly,we introduce the theory of optical tweezers and the condition of capturing particle;Secondly,we start from the Debye-type integral representation of the laser beam as a superposition of plane electromagnetic waves,the optical force on the microsphere particles is calculated quantitatively. Thirdly, the simulation results under given parameters are described. According to the simulation results, the relations between the optical trapping force and the main parameters of the system, including focus spot radius, the relative refractive index, the laser wave-length and power and so on, is discussed. Finally, induce and summarize the latest progress of research in the aspect of nanometer optical tweezers technology, and illustrate some application of advanced combination technologies in the improvement of installment structure, the precision of operation as well as the calibration in detail, and propose some conception and suggestions based on these.