Research On Some Key Problems In Femtosecond Laser Fabricating Micro-optics Devices

Femtosecond laser-based fabrication technology, which is one of the high precise mask-less fabricating technologies, has some special advantages in micro-optical devices fabrication. As the ultra-short pulse duration and ultra-powerful instantaneous power of the femtosecond laser, it can produce tiny heat effect and high fabricating precision. And the femtosecond laser can fabricate inside samples, so it has the ability of fabricating complicated 3D structrures.However, some problems related to the application of femtosecond laser-based fabrication technology need to be solved. The asymmetric of fabricated results and low efficiency are two common problems. Facing these two kind problems, the dissertation aims at how to improve on other research results.(1) Beam reshaping technology can amend the asymmetric of fabricated lesults by improving on the distribution of intensity of beam at the foci. Both of the two main methods can fabricate micro devices with good symmetry. One reshaping technology blocks beam's propagation at one dimension via slits, which can change the distribution of beam intensity at foci. This method is quite simple, but it waste big amount of beam energy at the same time. The other method reshapes the beam through lens group, and it can make the distribution on the space symmetric with high resolution. But the light circuit is complex and it is difficult to adjust.The dissertation puts forward one method which can reshape the beam to improve the symmetry of fabricated results through inserting one lens in the fabricating light circuit. This method is simple and has no added energy loss. After theoretical analyze, the effectiveness of this method is simulated and verified by experiments.(2) Femtosecond laser parallel fabricating methods are almost achieved via beam-splitter devices. Focusing the split beams can get multi-foci. And the distribution of multi-foci totally depends on the beam-splitter's parameters. So once the distribution need be adjusted, the beam-splitters always must be replaced firstly. It makes the method quite inconvenient.The dissertation proposes achieving parallel fabrication through the spontaneous multi-focusing which generates when the femtosecond laser interacts with materials. The multi-foci's distribution only depends on the intensity and some other beam parameters. So the distribution can be controlled through adjust the intensity or some other beam parameters. It makes the method easy relatively.The intensity distribution of spontaneous multi-focusing beam has been simulated. And the influencing factors have been obtained through simulation. In the experiments, multi-waveguides have been fabricated, and the distribution of waveguides can be controlled by adjusting the influencing factors.The dissertation makes some creative points as bellow:(1) One improved vertical fabricating method has been put forward. The method is rather much simpler than other improved fabricating method and it costs no more energy loss. Simultaneity it can get high precise symmetry.(2) One revolutionary parallel method has been put forward. The method realizes parallel fabricating by the spontaneous multi-focus. The intervals can be controlled much easily.