基于纳米等离子体近场增强的飞秒激光三维纳米加工技术研究

Due to the unique characteristics of ultrashort pulse width and extremely high peak intensity, femtosecond lasers have established themselves as excellent tools for high-precision and flexible fabrication of three dimensional (3D) microstructures. By taking advantage of the well-defined ablation threshold as well as the suppressed thermal diffusion, one can beat the diffraction limit by choosing the peak laser fluence slightly above the threshold value. However, due to the high nonlinearity of photoionization, the structuing process will become extremely sensitive to the fluctuation of laser intensity, especially when the laser intensity is near the threshold intensity. To address this issue, this research will focus on a far-field nanostructuring technique enabled by near-field enhancement of laser-induced nanoplasma in dielectric materials. By use of new methods to visualize and control ultrafast laser interaction with transparent materials, such as high-fidelity observation of nanograting evolution with high temporal and spatial resolution and dynamically adjusting of the interaction between growth and erasure of nanograting, we try to understand the underlying formation mechanisms of nanogratings. Furtherly, we will significantly improve the longitudinal fabrication resolution and uniformity, and then achieve stable and uniform 3D nanostructures.

由于极短的脉冲宽度和极高的峰值功率，飞秒激光可以深入透明材料内部实现高精度的复杂三维微纳米结构加工。利用飞秒激光烧蚀的阈值特性，原理上可以超越远场衍射极限的限制。但由于飞秒激光与透明材料相互作用的高度非线性特征，阈值附近的加工对激光功率波动等不稳定因素非常敏感，限制了该技术的实际应用。针对这一难题，本项目致力发展一种基于纳米等离子体近场增强的飞秒激光三维纳米加工技术。通过采用纳米光栅演化的高时空分辨观测和纳米结构生长与擦除的动态耦合调控等创新技术，在深入理解纳米光栅形成机制基础上，有效提高加工的纵向分辨率和均匀性，为实现稳定可控、大范围均匀的三维纳米加工奠定基础。

由于极短的脉冲宽度和极高的峰值功率，飞秒激光可以深入透明材料内部实现高精度的复杂三维微纳米结构加工。利用飞秒激光烧蚀的阈值特性，原理上可以超越远场衍射极限的限制。但由于飞秒激光与透明材料相互作用的高度非线性特征，阈值附近的加工对激光功率波动等不稳定因素非常敏感，限制了该技术的实际应用。针对这一难题，本项目提出并发展了基于纳米等离子体近场增强的飞秒激光三维纳米加工技术。在课题组发展的纳米光栅高保真观测技术的基础之上，采用时域脉冲整形、时空聚焦、界面调控等技术，发现了若干新的现象，为纳米光栅形成机制的理解提供了新的思路。在上述研究的基础上，获得了制备均匀纳米光栅的优化工艺，并成功应用于石英玻璃的选择性化学刻蚀、减小波导弯曲损耗、波导模场转换、圆形截面通道制备等，对光子芯片和微流控芯片等应用领域产生了一定的推动作用。