CAREER: Nanolithography Using Ultrashort-Pulsed Laser Processing

该学院早期职业发展（CAREER）计划资助支持基于激光的先进制造的基础研究，该制造能够在大面积上单步制造纳米级结构。目前的纳米制造工艺涉及多个步骤，并且不适合以具有成本效益的方式制造一种或定制的纳米结构。在这个项目中，超短脉冲激光器，它发射的闪光（脉冲）具有极短的持续时间，用于钻孔，切割和图案的材料与纳米级的精度。由于脉冲的持续时间很短（不到万亿分之一秒），激光脉冲的能量高度集中在材料中，创造了其他加工方法通常无法实现的条件。超短脉冲激光加工提供了显著减少附带损伤的关键优势，即破坏周围材料，从而提高了各种材料加工的精度。该项目推进了对电介质材料（如玻璃和金刚石）的超短脉冲激光加工的理解，这些材料通常用于显示面板，微电子和切割工具。该项目取得的进展使社会受益，因为它实现了一种新的纳米级图案化方法，减少了制造时间，降低了成本，并支持旨在培养训练有素的制造业劳动力的教育和推广计划。该项目提高了公众对激光和光学技术在日常生活中的认识，吸引年轻学生学习科学技术，并引导大学生从事先进制造业。新的纳米光刻方法是基于激光烧蚀，使用超短激光脉冲序列（脉冲串），其在时间上被调谐以创建自由载流子群体的本地化和增强激光能量的吸收。研究并控制超短激光脉冲与宽带隙光子晶体之间的非线性相互作用，以提高空间分辨率和能量吸收效率。该研究产生了关键工艺参数和相关纳米物理学的知识，使这种新的纳米制造方法成为可能。三种加工模式-钻孔，切割和投影（使用电子控制的空间光调制器作为可定制的光掩模）-进行了探索，并研究了每种模式所面临的独特挑战。利用瞬态泵浦-探测显微术和激光损伤阈值测量技术研究了电介质材料激光加工中的电子动力学时空过程。任意纳米结构的大面积图案化证明使用一个系统，集成了脉冲序列处理与掩模投影光刻。该项目增强了超短脉冲激光作为制造工具的能力，并为研究激光与物质在高于损伤阈值范围内的相互作用开辟了新的机会。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) Program grant supports basic research in laser-based advanced manufacturing that enables single-step fabrication of nano-scale structures over a large area. Current nanofabrication processes involve multiple steps and are not suitable for fabricating one-of-a-kind or customized nanostructures in a cost-effective manner. In this project, an ultrashort-pulsed laser, which emits flashes of light (pulses) with extremely short duration, is used to drill, cut and pattern materials with nano-scale precision. Because the duration of a pulse is so short (less than one trillionth of a second), the energy of the laser pulse is highly concentrated in the material, creating conditions that are not normally achieved with other processing methods. Ultrashort-pulsed laser processing provides the key advantage of significantly-reducing collateral damage, that is damaging the surrounding material, and thus improving precision in the processing of a variety of materials. This project advances the understanding of ultrashort-pulsed laser processing of dielectric materials, such as glass and diamond, which are commonly used in display panels, microelectronics and cutting tools. Advances resulting from the project benefits society by enabling a new method for nano-scale patterning that reduces manufacturing time and lowers cost, and by supporting an education and outreach program aimed at cultivating a well-trained manufacturing workforce. The project raises public awareness of laser and optical technologies in everyday life, attracts young students to science and technology, and guides college students to pursue a career in advanced manufacturing. The new nanolithography method is based on laser ablation using a sequence of ultrashort laser pulses (a pulse train) that is temporally tuned to create localization of free-carrier population and enhanced absorption of laser energy. Nonlinear interaction between ultrashort laser pulses and wide-bandgap dielectrics is studied and controlled to enhance spatial resolution and improve energy-absorption efficiency. The research generates knowledge of the critical process parameters and relevant nanoscale physics that enable this new nanofabrication method. Three processing modes - drilling, cutting, and projection (using an electronically-controlled spatial light modulator as a customizable photomask) - are explored, and the challenges unique to each mode are studied. Spatial and temporal electron dynamics, which play a key role in laser processing of dielectric materials, are investigated by transient pump-probe microscopy and laser damage threshold measurement. Large-area patterning of arbitrary nanostructures are demonstrated using a system that integrates pulse-train processing with mask-projection lithography. This project enhances the capability of ultrashort-pulsed lasers as a manufacturing tool and opens up new opportunities for studying laser-matter interactions in the above-damage-threshold regime.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.