Research On Ultrafast Micro-Nano Fabrication Technology And Application Based On DMD

In the past two decades,femtosecond laser micro-nano-fabrication technology,as an ultraprecise laser 3D printing method,has been widely used to fabricate various micro/nano structures,in micro-electromechanical systems(MEMS)devices,biomedical engineering,photonic devices.,applications in the fields of optical metamaterials and other fields have grown rapidly,providing important technical support for key basic research and cutting-edge research and development.However,since the traditional laser processing technology usually adopts a single-focus scanning method,and uses a precision displacement platform or a galvanometer to realize structures with different geometries,the operation cost is high,and the processing speed is limited by the laser scanning sequence.The disadvantages are even more pronounced when constructing structures such as octagonal trusses,making it difficult to put this technology into practical large-area fabrication.In this work,combined with binary computational holography,we utilize digital micromirror arrays(DMD)to realize ultrafast laser micro-nano fabrication of arbitrary 3D structures.By loading the calculated binary holographic pattern onto the DMD and modulating the wavefront of the femtosecond laser irradiated on the DMD,multiple laser foci can be simultaneously generated and independently controlled,and processed in parallel at the DMD refresh frequency of 20 k Hz.It only takes 1 s to output 20000 × N laser focal points(N is the number of parallel focal points)for 3d structure processing.The performance parameters(maximum field of view and minimum step size)and resolution of the machining system were characterized in the experiment,and the fourth-order supercritical lens and microtube structures were rapidly fabricated using this processing technology.The large area rapid fabrication of 3D structures was demonstrated in the experiment.The main work of this paper can be summarized as follows:(1)Based on the light field theory under the tight focus of high NA objective lens,the complex amplitude distribution of the focus at the entrance pupil corresponding to the three-dimensional position offset of focal plane space is deduced.Combined with binary computer-generated hologram technology,the binary hologram loaded on DMD is calculated and simulated.Based on the theoretical derivation,a calculation method of multi parameter tunable light field based on DMD is proposed.(2)Design the optical path based on DMD fast micro-nano fabrication system and realize dispersion compensation;Analyzing and calculating the processing performance of the system(maximum processing field of view and minimum scanning step).When all devices in the system are certain,calculate the processing performance of the system under different parameters of objective lens.By processing multiple groups of suspended lines under different power to characterize the transverse resolution and axial resolution of the system,the two-dimensional plane structure and three-dimensional structure with different complexity are processed rapidly by single focus,and the processing time is completed in a few seconds.In the experiment,single focus and multi-focus parallel processing of three-dimensional structure are used respectively.From the experimental results,it can be seen that parallel processing will not lead to the reduction of resolution and structural deformation,but can further improve the processing speed by increasing the output of laser power.(3)According to the resolution data of the processing system,a simpler and more efficient fourth-order phase processing method is proposed to meet the phase difference conditions of different orders in the fourth-order phase type supercritical lens,and the manufacturing time of a single super structured lens is only 2S.From the optical characterization,it can be seen that the experimental measurement is basically consistent with the theoretical simulation.Combined with the mobile positioning of the displacement platform,a large area fourth-order phase supercritical lens array is prepared in a short time.In addition,the microtubule structures with different sizes,arrangement and complexity are fabricated ultra fast.The excellent machining performance of the rapid micro-nano fabrication system based on DMD is verified.