Additive Manufacturing of Freeform Optics

Abstract

Tremendous optical elements have been designed for more functionalities. However, the complex optical structures and multi-element fabrication or alignments of advanced optics have been highly limited by the capability of traditional manufacturing, which inevitably limits the development of further study in optics. Additive manufacturing (AM), so-called 3D printing, keeps increasing the attention in both academics and industries by its potential to produce complex optical geometrics, rapid optical system prototyping, and multi-functional optical applications. To meet the requirements for more applications, it is always desirable to create creative printing methods and strategies and develop new materials or optimize existing materials for different 3D printing technologies. This dissertation mainly focuses on how the different method is utilized as powerful tool to develop optical elements with high resolution, high transparency, and proper functionalities. Besides, novel material for different 3D printing techniques has been developed. IR pulsed laser printing method and Two-photon polymerization (TPP) printing method of optical silicone and inorganic glass are the subjects of this work. In the first part of chapter 1, the background of 3D printing optics is introduced, including different types of manufacturing methods and the different types of materials paired with each manufacturing technique. The second part of chapter 1 briefly introduces the manufacturing standard for proper optical application, particularly imaging optics. The third part of chapter 1 explains the development of micro-optics and the manufacturing method. The final part mainly discusses the direct laser writing (DLW) strategy and the laser types for different polymerization concepts such as thermal curing and TPP. Chapters 2 and 3 focus on describing how we use IR pulsed laser hybrid printing methods to fabricate different optical elements. It mainly introduces the thermal curing performance and the manufacturing process for spherical surfaces, freeform surfaces, and multi-component applications. The optical properties of PDMS and Silsesquioxane were evaluated for different optical applications. Chapter 4 explains glass fiber-feed printing mainly. We mainly introduce the manufacturing process and optimization. It analyzed how we calibrate the printing method by printing resolution analysis. The heat feedback and control system have been induced in the manufacturing process to maintain the uniformity of the glass optics. The spherical, freeform, and objective were printed to evaluate the printing resolution. Chapter 5 introduce the principle of two-photon polymerization, the modeling of polymerization processes, and the 3D printing strategy through the concept of TPP. We discussed the TPP condition and the relevant photo-material interaction. The printing system setup, equipment, and strategy were introduced to evaluate the advantages and disadvantages of different components manufacturing. Chapters 6 and 7 show the TPP printing process to fabricate inorganic silica glass micro-optics with liquid silica resin (LSR) and the photo-based AM technique. It introduces how the LSR was synthesized using sol-gel chemistry and how it was optimized for fabricating different optical elements. The properties of LSR, including curing performance, printing behavior, optical properties before/after thermal treatment, etc., were studied. Micro-optics and optical systems were fabricated, and their performance was evaluated. Lastly, chapter 8 discusses some work that can be done in the future to keep improving the mechanical and optical properties. We highlighted the increasing printing speed to fabricate the optical element and the potential for high production. The printing resolution can be improved in the future.