The Polarization And Amplitude Distribution Impact To The Optical Trappingforce For Incident Beam

Optical trapping is an effective method to manipulate small particles which is based on radiation pressure of light. Since Ashkin successfully trapped and manipulated the micron-sized glass ball in three-dimensional space by the highly focused laser in 1986, the optical trapping technology becomes more and more widespread attention. In recent years, it becomes an important research tool in many domains,such as biomedical, chemistry, physics, spectroscopy and micro-machining. This thesis, it includes the following aspects:The first chapter introduces the research progress of the theory and experimental in the optical trapping. The second chapter presents the vector diffraction theory and the Rayleigh scattering theory for the radial force calculation.The third chapter reveals the important effects of optical trapping by compared with linear polarization, radial polarization and cylinder vector beams. In the fourth chapter,we study the amplitude of the incident light to the effects of optical trapping forces by the Gaussian beam and the Laguerre-Gaussian beams,respectively. The fifth chapter analyses the near-field optical trapping properties with the solid immersion lens. The summary and outlook are given in the final chapter .In the thesis, we first calculate the energy density distribution of the radial magnetic field in the focal region by the vector diffraction theory. We can capture the different radius particles in adjust to change the truncation parameter. In particular, the radial polarization is very useful to capture the highly absorption rate particles. By studing the capture characteristics of Laguerre-Gaussian beam, we find that the truncation parameter of the double-ring radial polarized beam to be about 1.3, it produces a three-dimensional dark spots which is can be used to capture the large refractive particles . When the truncation parameter is near to 2 by adjusting the size of the pupil, a three-dimensional bright spot can be producted which can be captured the small refractive particles in the three-dimensional space .