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Theoretical and experimental investigations on pulse front deformations for laser material processing using ultra-short laser pulses

使用超短激光脉冲进行激光材料加工的脉冲前沿变形的理论和实验研究

基本信息

批准号：
244610156
负责人：
Professor Dr. Peter Loosen
金额：
--
依托单位：
Lehrstuhl für Technologie optischer Systeme (TOS)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2016-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/244610156?language=en
关键词：
Theoretical experimental investigations pulse front

项目摘要

During the last years ultra-short laser pulses have been established in several application areas, to process different materials with high accuracy. By reducing the pulse duration a higher power density can be achieved at a constant average laser power which enables the excitation of nonlinear processes and thus an efficient absorption of the laser radiation.In combination with scanner systems large work pieces can be machined at high process velocities, because high velocities and accelerations of the focused laser beam with respect to the work piece are feasible.For the propagation of ultra-short laser pulses through dispersive optical elements the difference between group and phase velocity leads to delay (propagation time difference or PTD) between pulse and phase front. For a pulse which propagates parallel to the optical axis through a positive lens the PTD maximum will occur along the chief ray, whereas the PTD reaches a minimum along the marginal rays, due to the minor glass thickness of the lens. This effect leads to an increase of the pulse duration in the focal region. Some principles to compensate the PTD effect for systems with light incidence parallel to the optical axis are discussed in the literature.Both simulative and experimental preliminary studies demonstrate a strong dependency of the PTD on the field angle. For optical systems for laser scanners this causes pulse deformations and durations depending on the scan angle. First simulations show that comparatively small scan angles of 6° lead to a temporal pulse expansion of about 100 fs for conventional scanner optics. For sensitive processes as for example the processing of transparent dielectrics with pulse durations of about 500 fs, scan angle depending results can be expected.Goal is the development of new optic design concepts and methods to design focusing lenses for laser scanners with homogeneous pulse properties all over the scan range. The working schedule contains the fields modeling/simulation, concepts/design methods and experimental validation. The field modeling/simulation contains investigations of different geometrical and wave optical methods and the analysis of theirs validity for the description of pulse deformations caused by focusing lenses. At once a measurement method shall be set up, to investigate the pulse front behind focusing lenses for different field angles and compare the results with the simulation. Based on the simulation and the measurement results, different design methods will be pursued and combined with applicable simulation techniques. In conclusion the design of different exemplary objectives is intended, as well as the experimental characterization by measurements and also experiments of processing glass samples.

在过去的几年中，超短激光脉冲已经在多个应用领域中建立，以高精度加工不同的材料。通过减少脉冲持续时间，可以在恒定的平均激光功率下实现更高的功率密度，从而能够激发非线性过程，从而有效地吸收激光辐射。与扫描仪系统相结合，可以以高加工速度加工大型工件，因为聚焦激光束相对于工件的高速度和加速度是可行的。通过色散光学元件的短激光脉冲，群速度和相速度之间的差异导致脉冲和相波前之间的延迟（传播时间差或PTD）。对于通过正透镜平行于光轴传播的脉冲，PTD最大值将沿着主光线出现，而PTD由于透镜的较小玻璃厚度而沿着边缘光线达到最小值。这种效应导致聚焦区域中的脉冲持续时间增加。文献中讨论了平行于光轴入射光的系统中PTD效应的补偿原理，模拟和实验初步研究表明PTD效应与入射角有很强的依赖关系。对于激光扫描仪的光学系统，这会导致脉冲变形和持续时间，具体取决于扫描角度。第一次模拟表明，6°的相对小的扫描角导致常规扫描仪光学器件的约100 fs的时间脉冲扩展。对于敏感的工艺，例如处理透明陶瓷，脉冲持续时间约为500 fs，扫描角度依赖的结果可以预期。目标是开发新的光学设计概念和方法，设计激光扫描仪的聚焦透镜，在整个扫描范围内具有均匀的脉冲特性。工作计划包括现场建模/仿真，概念/设计方法和实验验证。场建模/仿真包括不同的几何和波动光学方法的调查和分析其有效性的描述聚焦透镜引起的脉冲变形。应立即建立测量方法，以研究不同视场角下聚焦透镜后的脉冲前沿，并将结果与模拟结果进行比较。根据模拟和测量结果，将采用不同的设计方法，并与适用的模拟技术相结合。总之，不同的示例性物镜的设计是意图，以及通过测量和加工玻璃样品的实验的实验表征。