Study On Femtosecond Laser Microscopy Manipulation System

In this dissertation,the femtosecond laser microscopy manipulation system isstudied. The main contents are classified as follows:1. The particles in the range between the applicable regime of ray optics theory (ROT)and the Rayleigh regime (so-called the medium-sized particles) are focused on. Byusing ROT and the generalized Lorenz-Mie theory (GLMT), axial optical forcesexerted on the particles and their dependences on particle sizes and beam waistsare discussed. Furthermore, by comparing the numerical results of these twotheories, the applicability of the GLMT to particles of arbitrary size and thelimitation of ROT in the region of small particle size are analyzed. A new criterionof the applicable region of ROT is obtained. The theoretical results will be of greathelp to the design and optimization of the most efficient optical trap.2. The lateral optical force applied on the dielectric particles by the femtosecond lasertweezers is theoretically analyzed. Taking femtosecond laser pulse train as thesampling of the CW light, a numerical model of the induced lateral forces onmicrometer-sized sphere is founded and the formulas are derived. The numericalsimulation shows that the lateral optical force applied by femtosecond laser pulsetrain can eliminate the Brownian movement of the particles and stably trap them.3. The femtosecond laser microscopy manipulation system was realized. A key partof the system is a commercial inverted research microscope (IX71, Olympus).Femtosecond laser pulses were introduced into the microscope through an imagepath from the lift side port. We designed motorized specimen stage with aresolution of 0.2 μm and modified the image parts. Based on these grounds, anexperimental instrument of femtosecond laser microscopy manipulation systemwas built.4. On our femtosecond laser microscopy manipulation system, stable optical trappingof micrometer-sized objects such as human red blood cells (RBCs), white bloodcells (WBCs), smaller virus and polystyrene microbeads was observed. Wemeasured the trapping capabilities of femtosecond laser tweezers in comparisonwith that of CW laser tweezers.5. The photodynamic therapy based on the two-photon excitation was performed onthe liver cancer cells with a single cell resolution. The experimental results showthat our system will be a potential powerful tool in biology.6. At last we make some suggestion of the future work, which gives a direction forfurther study on femtosecond laser microscopy manipulation system.