高深径比微通道的飞秒激光空间光束整形加工方法研究

Microchannels are the key functional structures of many micro- devices/systems. The microchannels applied in these micro- devices/systems have a feature of small diameters (micrometer scale or even nanometer scale), high aspect ratio (several tens or up to a hundred), small taper, and so on. Traditionally, the semiconductor technology is used for the preparations of the microchannels. As the manufacturing process is very complex and it is difficult to prepare three-dimensional microchannels by using the traditional semiconductor technology, a novel method is crucial to be developed for the fabrication of microchannels. Due to the advantages of high flexible and three-dimensional high precision, femtosecond laser becomes an ideal option for the fabrication of microchannels. However, with the continuous requirements of extremely high quality and precision, there are still challenges and questions for the fabrication of microchannels by using femtosecond laser, such as ultrafast laser-material interactions mechanisms, high efficiency, selective and controllable fabrication, and so on. Based on these challenges and questions, this project proposes a new method for the fabrication of high quality and high aspect ratio microchannels in transparent materials by spatial shaping femtosecond laser Gaussian beam into Bessel beam combining with liquid-assistance and chemical etching. At the same time, the multiscale models are established to describe the nonlinear and nonequilibrium complex femtosecond laser-material interactions, including structure evolutions, phase change mechanisms, material ablation and formation of microchannels. The proposed project will provide theoretical basis and manufacturing techniques for the high efficiency fabrication of microchannels by femtosecond laser to meet the continuous requirements.

微通道是许多微型器件/系统的关键功能结构。应用在这些微型器件/系统的微通道具有直径尺寸小(微米尺度，甚至纳米尺度)、深径比高(数十或近百)和锥度小等特征。传统微通道的制备采用半导体工艺，但制备过程极其复杂且难以实现三维网络型微通道的加工，因此亟需探索新的制造方法。飞秒激光以其三维高精度加工的优势为复杂网络型微通道的制备提供了理想的工具，但在作用机理、质量保证、可重复性及加工效率等方面仍存在许多问题及挑战。基于此，本项目提出通过空间光束整形将飞秒激光高斯光束转变为贝塞尔光束，结合液体辅助烧蚀和化学刻蚀，实现在透明介质内高质量、高深径比微通道的高效率可控制备；建立飞秒激光与材料作用的多尺度模型，揭示被加工材料的结构演化、相变机理、去除机制及微通道的形成过程，为高效率地制备满足更高要求的微通道提供理论基础和技术储备。

微通道是许多微型器件/系统的关键功能结构。应用在这些微型器件/系统的微通道具有直径尺寸小、深径比高和锥度小等特征。传统微通道的制备采用半导体工艺，但制备过程极其复杂且难以实现三维网络型微通道的加工，因此亟需探索新的制造方法。飞秒激光以其三维高精度加工的优势为复杂网络型微通道的制备提供了理想的工具，但在作用机理、质量保证、可重复性及加工效率等方面仍存在许多问题及挑战。基于此，本项目在理论上研究空间整形的飞秒激光光强分布规律，实验上利用空间光束整形、温度场辅助烧蚀及后续辅助处理等方法实现高质量、高深径比微通道的高效率、可控制造。项目整体进展顺利，研究工作按计划展开落实，完成了所有的研究内容并取得了一系列的科研成果，在国际主流期刊上发表SCI论文9篇；申请国家发明专利1项。根据项目研究内容要求，主要研究成果如下：.① 研究了空间整形的飞秒激光光强分布规律：从几何光学角度，分析了空间整形光束特征参数的变化规律，得到了整形系统的最佳参数组合；从波动光学的角度，基于锥透镜、凸透镜对入射光波前相位的调制机理与光束在自由空间中的传播机制，建立了空间整形光路系统的理论模型，分析了锥透镜顶端偏差和边界衍射效应对空间整形光束的光强分布影响规律，以指导加工实验；.② 设计并搭建了空间光束整形的飞秒激光加工系统，并开展了高深径比微通道加工实验，较未整形的飞秒激光高斯光束加工方法在加工效率和深径比等方面有较大提升；.③ 针对飞秒激光在加工透明介质时效率低、微通道的深径比不高的问题及挑战，提出了温度场辅助的飞秒激光高效率加工方法，有效地提高微通道的加工效率、加工长度和材料的去除体积；.④ 针对飞秒激光加工效率低的问题及挑战，提出了基于微透镜阵列空间光束整形的飞秒激光并行制造方法，有效地提高了加工效率和加工精度；.⑤ 运用空间光束整形的飞秒激光制造方法，实现了环形微纳结构的高效率、一次成形制造。