Experimental and Theoretical Study of Femtosecond Microscale 3D Light Field Projection and Its Application in Multiphoton 3D Light Field Lithography

元材料是一种周期性材料，它允许微观结构设计，并能够提供天然材料中不存在的独特光学、物理、化学和生物特性。在这个项目中考虑的超材料是3D的，它们的几何形状是三维的，或者是2.5D的，它们的几何形状是在一个平面上定义的，但是这个平面可以堆叠成一个3D结构。人们非常希望有一种微加工技术，可以在大范围内提供这些结构的高速、高分辨率制造。现有的制造技术既可以提供足够高的分辨率来制造2.5D/3D特征，也可以提供足够高的吞吐量来覆盖大面积，但不能同时提供这两种技术。同时具备这两种能力的先进制造工艺对于元结构的商业化至关重要。该奖项将支持研究利用飞秒激光将3D虚拟物体投影到光刻胶（一种暴露在光线下会发生性质变化的聚合物材料）中，作为实现高速、高分辨率制造的方法。这可能是可行的，因为飞秒激光可以在一个3D光场投影中实现超过10,000个焦点，可以实现更高的处理速度。关于3D投影和光抗蚀剂之间复杂的非线性相互作用的知识差距将使用计算和实验方法来解决。如果成功的生物传感/检测和排放/吸收控制表面可以实现，并有助于美国国防和健康相关利益。该奖项还将促进未来劳动力的培训，因为各级学生都将获得2D和3D微制造技术的接触和经验。其他教育外展活动包括让高中教师参与研究，并通过研究网站、会议参与和期刊出版物传播研究结果。本研究的技术目标是建立一种新的基于飞秒压缩三维光场投影的三维光刻方法。如果成功，它将实现高速（与单点多光子光刻相比），高分辨率（等于或优于波长的一半）在大范围内制造复杂的2.5D/3D微结构。本研究的技术范围包括：1)结合一般像散高斯光束跟踪和全波模拟的混合波分析方法，可以使用最小的计算能力对大型光学系统中的光聚焦进行高精度波型分析；2)确定多光子3D光场光刻固化光刻胶的应力/应变场和相关变形；3)设计并制造了飞秒压缩3D光场投影仪测试平台，以验证从飞秒体素投影中固化光刻胶图案的理论预测尺寸和形状。本研究将显著促进以下领域的基本认识：光刻胶中的非线性飞秒光传输/聚焦/吸收利用飞秒脉冲光重建三维虚拟物体以及飞秒三维光场投影在各类型2.5D/3D微结构大面积三维微加工中的可行性。该奖项反映了美国国家科学基金会的法定使命，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。

Meta materials are periodic materials that allow microstructure design and are able to provide unique optical, physical, chemical and bio properties that do not exist in natural materials. The meta-materials considered in this project are 3D, where their geometry is described in three dimensions, or 2.5D, where the geometry is defined in a plane, but the plane can stack to make a 3D structure. There is a great desire to have a microfabrication technique that can provide high speed, high resolution fabrication of these structures over large areas. Existing fabrication techniques can provide either sufficiently high resolution to fabricate the 2.5D/3D features, or sufficiently high throughput to cover large areas, but not both simultaneously. An advanced manufacturing process capable of both is critical for the commercialization of the meta-structures. This award will support research on using femtosecond laser enabled 3D virtual object projections into a photoresist (a polymeric material that experiences property changes when exposed to light) as a method to achieve high speed, high resolution fabrication. This is potentially feasible as a femtosecond laser, which can realize over 10,000 focal spots in one 3D light field projection, can enable higher speed processing. Knowledge gaps regarding the complex, non-linear interactions between the 3D projections and the photoresist will be addressed using computational and experimental approaches. If successful bio-sensing/inspection and emission/absorption controlled surfaces may be realized and contribute to U.S. defense and health related interests. The award will also facilitate training of the future workforce as students across all levels will gain exposure to, and experience in 2D and 3D micro fabrication technologies. Additional educational outreach activities include engaging high school teachers in the research, and disseminating the findings through research websites, conference participations and journal publications. The technical objective of this research is to establish a new 3D lithography method based on femtosecond compressed 3D light field projection. If successful it will realize the high-speed (compared with single-spot multiphoton lithography), high-resolution (equal or better than half of the wavelength) fabrication of complicated 2.5D/3D microstructures over a large area. The technical scope of this research includes; 1) a hybrid wave analysis approach combining general astigmatic Gaussian beam tracing and full wave simulation to enable high accuracy wave type analysis of light focusing in large optical systems using minimum computational power, 2) determination of stress/strain fields and the associated deformation of cured photoresist from multiphoton 3D light field lithography, 3) specification and fabrication of a femtosecond compressed 3D light field projector test bed to verify the theoretically predicted size and shape of cured photoresist patterns from femtosecond voxel projections. This proposed research will significantly advance the fundamental understanding in the following areas; non-linear femtosecond light transport/focusing/absorption in photoresists; 3D virtual object reconstructions with femtosecond pulsed light; and the feasibility of femtosecond 3D light field projection in 3D microfabrication of each type of 2.5D/3D microstructures over a large area.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.