| Microlens has developed a wide range of applications in space flight, biomedical, laser technology, national defense and other fields, while normal lens grinding process and other manufacturing techniques of microlens are fully constraint in fabricating spherical microlens. Spherical lens are known to induce large aberrations during imaging, which need to be reduced by multi-lens combination. That is totally unsuitable in the application of mirolens. So to fabricate aspheric lenses with small aberrations is a better solution. Femtosecond Laser Two-Photon Polymerization Fabrication technology provide a new method of fabricating aspheric microlens, with its advantages of high precision fabrication and free designing of micro structures.In this thesis we discussed the advantages in imaging of aspheric microlens by software stimulation instead of complex optical light calculations and found that with the same radius and height there is a decrease incline of aberrations of spherical, rotating parabolic and rotating hyperbolic microlens in order. Then we manufactured spherical rotating parabolic and rotating hyperbolic microlens with radius of 20 m and 10 m in height by Femtosecond Laser Two-Photon Polymerization Fabrication and made comparisons with each other by focusing tests and imaging tests, got the same result of aberrations as software stimulation and in additional found the above three microlens have a decrease trend in view size in order.In order to fabricate microlens with large size, we firstly explored the largest point step and line step that can make 100% coverage by increasing them step by step in the condition of different objectives. Secondly we applied the largest point step and line step mentioned above in fabrication with the purpose of lowering the"point cloud"and duration of fabrication. From the experiment, we discovered that when 60X objective is applied in the fabrication process, the largest point step and line step need to be limited in 300nm while it can make 100% coverage when we set point step and line step to 700nm by using 25X objective in the fabricating period. Thirdly we improved the fabrication method by fabricating the"shell"instead of the whole microlens, thus dramatically reduced the total volume that need to be fabricate. Then we increased the working range by using the objective with lower magnification. We successfully fabricated aspheric microlens with radius of 200 m by 25X objective with point step 500nm, line step 500nm and 100nm layer step, and fabricated aspheric microlens with radius of 400 m by 10X objective under the point, line and layer step of 700nm, 700nm, 200nm. and make imaging and tests on them. Aim to make the 10°divergence angle laser diode collimation, we designed and fabricated a suitable aspheric microlens with radius of 400 m and make imaging and focusing tests on it. Through the tests we found that its imaging quality was not as good as what we manufactured before, considered it with its SEM image we made a conclusion that the over larger point step, line step and in sufficient laser power would be the main reason that caused the worse tests result.At the end of the thesis, we made an outlook of the technology of Femtosecond Laser Two-Photon Polymerization Fabrication and made proposals of a elliptical microlens which can be applied on collimating edge emission laser diode and made"point cloud"data by a self programmed Visual Basic script. This will be a new concept of collimating edge emission laser diode and bring a technological revolution in this field. |
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