Design Of A 3D Direct Laser Writing System Using A Continuous-wave Laser

3-D direct laser writing(DLW) system, which is based on two-photo absorption, can expose the photoresist in a small volume where the lased focus is located. However, the laser can propagate through the photoresist without a chemical reaction in the other areas, because that for a two-photo absorption, belowing a certain illumination threshold, the photographic plate shows no or only little darkening effect even if it is expose for a very long time. A 3-D structure can be exposed while the laser focus is scanning. Nowadays, a femtosecond laser is used in most of the directing laser writing systems. But the expensive femtosecond laser increases the cost of the DLW system, it limits the DLW system's popularization in industrial production. In this paper, we used a 473 nm continuous-wave laser to build a DLW system. The DLW system has been studied mainly from the following aspects.(1) The article analyzed the methods and key points of DLW system. The significance, principle, and characterization of two-photo absorption were reviewed. Then, the factors which associated to the range and probability of cross-linking reaction were deduced. We systemically discussed the methods and development process of the DLW system based on continuous-wave laser, including the methods of light path adjustment, auto focus, creating the coordinate of the micro-device and optimization of scanning paths, compensating the error added by the slant of substrate.(2)We give a method of process parameter optimization for DLW system. Through experiments, we analyzed the effect of exciting laser intensity, the scanning speed, the space between the x, y direction and the Z direction respectively, and then got the optimization process parameters. Finally, using this system, we succeed in fabricating some micro-devices, such as a square hole, spiral of Archimedes and 3D-photonic crystal.