Development of single element detection imaging systems and femtosecond laser micromachining for additive manufacturing processes

Abstract

The development of ultrafast laser imaging and micromachining systems for use in integrated material modification and additive manufacturing setups is discussed. This thesis is organized into seven Chapters. The first chapter presents a brief overview and introduction of ultrafast lasers and the benefits of using them for linear and nonlinear microscopy and imaging as well as amplified laser material modification. Chapter two demonstrates the many capabilities of the amplified ultrafast laser machining system in the context of additive manufacturing (AM). The significant results here include the ability to process AM components by creating a surface finish to a certain specification, generating micro-cone structures on the surface for modifying wetting characteristics, and writing nanogratings onto the components for encoding numerical counterfeiting information. Chapter three shows the results of using the ultrafast laser micromachining in combination with spatial frequency modulated imaging (SPIFI) to produce enhanced resolution images in multiple linear and nonlinear modalities. Chapter four extends SPIFI to a previously unknown capability in which the imaging system is constructed in such a way as to acquire interferometric axial sensitivity. This is significant as it opens up the world of surface metrology and imaging the phase content of objects with enhanced resolution. The fifth chapter highlights an imaging system where SPIFI is used to gain enhanced resolution in multiple dimensions simultaneously. Chapter six provides a review of a focusing technique called simultaneous spatial and temporal focusing (SSTF) which can be utilized in a wide range of microscopy and micromachining applications and mitigates many problems ultrafast lasers have when interacting with materials and acquiring images. The final chapter provides general conclusions and an outlook to the future of using amplified ultrafast lasers to provide in-situ process monitoring for additive and subtractive manufacturing.