Research On Fabrication Of Microstructures And Particles Manipulation By Femtosecond Laser

Nonlinear processes occupy the leadership mutually during the interaction between materials and femtosecond laser due to the short pulse width as well as the extremely high pulse peak power of the laser. This kind of nonlinear processes is limited by the threshold field intensity, thus, the femtosecond laser could induce different kinds of spatial microstructrues in materials. In recent years, optical functional microstructures inside or on the surface of the material induced by the femtosecond laser has received more and more attention. Optical tweezers are advantaged technology which can trap and control the particle by the radiating force. Optical tweezers focused by the femtosecond laser even could induce the non-linear phenomenon during the trapping process. In this thesis, firstly, we introduce several methods to fabricate the optical functional microstructures, and we also give theoretically investigation of the interactions between the femtosecond laser pulses and materials. Secondly, the femtosecond laser cell micromanipulation system was built up. The thesis can be summarized in detail as follows:Tightly focused femtosecond laser induced a quasi-periodic void microstructu-re and filamentation structures inside bulk glass due to the dynamic transformation between Kerr self-focusing and self-defocusing from plasma. Based on this, we successfully generate optical vortex with computer-generated hologram (CGH) inside glass by femtosecond laser pulses without any pre-or post-treament of the material. The restructured optical vortex beam with high fidelity could be achieved by using a collimated He-Ne laser normal incident on CGH. The first order diffractive efficiency is about 19.6%Microstructural modifications of amphous alloys and ZnO induced by femtosecond laser pulse have been investigated experimentally. Field launch electron microscope, X-ray diffraction and the energy dispersive X-ray have been carried out to test the the microstructures after femtosecond laser radiation. The morphology of amorphous alloys and ZnO after radiation has been investigated. We focus on the formation mechanism of those near wavelength and the alternation corrugated micro-nanometer structures. The origion of those microstructures is discussed.Vortex femtosecond laser was used to induce microstructures on the surface of amorphous alloy. Modification of microstructures under different ablative conditions has been investigated experimentally. The relationship between the distributions of many kinds of microstructures and intensity distribution of the vortex femtosecond laser was discovered. It is found that the distribution of surface microstructures could be controlled by the topological change as well as the pulse numbers. We proposed the possible mechanism of the formation of those coral-like structures.Femtosecond laser cell micromanipulation system was realized. Stable optical trapping of human red blood cells and microzyme cell was achieved by this system. Experiment results were qualitatively analyzed. Hydromechanics method was carried out to test the optical force and it was found that optical force is in piconewton order.