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针对传统的二次非球面折射型激光扩束器存在不易加工、装调困难、体积大、重量大,特别是难以获得高填充比阵列透镜等不足,提出了一种利用衍射型台阶化面型近似二次非球面的激光扩束器方案,结果表明:对于典型的束腰半径为2mm的高斯光束,衍射型激光扩束器可实现2.8倍的理论扩束比。为了保持扩束过程中激光模式的稳定性,提出了不同区域给定不同台阶数的两类复合结构,解决了扩束过程中保真度和二元衍射元件加工特征尺寸无法同时满足的问题,改进后的系统保真度达95.82%,各区域最小光刻线宽均大于2μm,能够满足现有光刻加工技术要求。对影响系统保真度主要误差的分析结果表明:离轴误差在-1~1mm,目镜和物镜倾斜误差分别小于0.1mm和1.68mm时,系统保真度仍大于95%,方便装调。
Aiming at the disadvantages of traditional secondary aspheric refractive laser beam expander, such as difficult to process, difficult to set up, large volume and heavy weight, especially difficult to obtain high fill ratio array lens, The results show that for a typical Gaussian beam with a waist radius of 2 mm, the diffractive laser beam expander can achieve 2.8 times the theoretical beam expander ratio. In order to maintain the stability of the laser mode in the process of beam expansion, two types of composite structures with different steps given in different regions are proposed to solve the problem that the fidelity of the expanding process and the processing feature size of the binary diffraction element can not be satisfied at the same time, The improved system fidelity reaches 95.82%, and the minimum lithography line width in each area is greater than 2μm, which can meet the existing lithography processing technology requirements. The main error of the system fidelity analysis results show that: the off-axis error of -1 ~ 1mm, eyepiece and objective tilt error of less than 0.1mm and 1.68mm, the system fidelity is still greater than 95%, easy to install.