Research On Parallel Femtosecond Laser Fabrication Technologies With Spatial Light Modulator

Femtosecond two-photon polymerization technique has specific advantages in the fabrication of complex three dimensional micro-and nanodevices. However, the conventional two-photon polymerization technique is a serial technique based on the scanning of single laser spot. So, it is time consuming, which hinders its wide application in industrial production. Flexible and controllable laser intensity distribution can be achieved with computer generated holograms by laser modulation. This dissertation combines two-photon polymerization technique and laser modulation technique, presents a parallel and fast two-photon polymerization technique. The feasibility is demonstrated and the fabrication process is investigated by theoretical analysis and experiments. Several functional microdevices are designed and fabricated as well as applied.Laser modulation and holograms generating technique are studied firstly in this dissertation. The structure and principle of liquid on crystal spatial light modulator are introduced. The process of laser modulation is theoretically analyzed with Jones matrix theory and factors affecting laser modulation are discussed. A phase distribution model is build by scalar diffraction theory. Then, the theory and flow chart of several popular algorithms for computer generated holograms are explained. The pros and cons in the uniformity of generated intensity distribution and optical efficiency of above algorithms are compared.Besides, projection two-photon polymerization technique with liquid crystal spatial light modulator is presented. A system for projection two-photon polymerization is built and the feasibility of this technique is demonstrated. Femtosecond laser is modulated into curve and plane patterns for the fabrication of microstructures with single exposure, which reduced the processing time greatly. Experiments show that longer exposure time and increasing the density of laser spots can leads to microstructures with smoother surface. Theoretical calculation shows that laser intensity distribution has a significant effect on the profiles of fabricated microstructures.Finally, femtosecond Bessel beams are achieved by phase modulation with spatial light modulator. The parameters of femtosecond Bessel beams can be flexibly controlled. Cylinder microstructures are fabricated with a single illumination by focusing femtosecond Bessel beams. The relationship between the size of cylinder microstructures and the parameter of computer generated holograms is investigated. Thus, the size of cylinder microstructures can be precisely controlled without any modification of optical elements and path. Microtubes can also be fabricated rapidly by moving femtosecond Bessel beams along the optical axis. With this method, the height, period and distribution of microtubes can be well controlled. Slant microtubes are achieved as well by moving femtosecond Bessel beams along a direction with an angle to the optical axis. The diameter and the top profile of microtubes can be modulated by the parameter of processing and computer generated holograms. On this basis, the application of microtubes in bioscaffolds and cell research are studied. Fabricating bioscaffolds with femtosecond Bessel beam can reduce the processing time greatly. The capture and release of breast carcinoma cells and Mouse fibroblast cells are realized successfully with above microtubes, which has important value on the study of cell motility, growth, division and proliferation in a confined environment.