Abstract
3D printing refers to the fabrication method where a three-dimensional object is created from a digital 3D model. A wide range of technologies are available for 3D printing today, starting from the commercially available stereolithography (SLA) resin printers to the high precision two-photon polymerization lithography (TPL) system. Compared to the traditional manufacturing techniques 3D printing is gaining popularity due to the flexibility in design, reduced manufacturing cost and the capability to fabricate arbitrary shapes. These features along with its rapid prototyping ability makes 3D printing an excellent choice for the fabrication of optical components such as lenses, waveguides, and imaging systems. However, quality of the parts produced by different printing techniques and the limited choices of high-optical quality materials pose a major challenge in deciding which 3D printing technology is to be used. This thesis explores the features of two different 3D printing techniques, the hobbyist-grade SLA technique which uses VAT polymerisation and the high precision TPL which uses voxel polymerisation, for the fabrication of optical components. The study first introduces a methodology that can improve the resolution of commercially available low-cost resin printers to suite it for the fabrication of optical components. Although various methods of optical component fabrication have been reported, to date there has been no demonstration of a high throughput and cost-effective method that can suit meso-scale (100µm to 5mm) component fabrication. Resin printers use layer-by-layer fabrication, which improves the fabrication time at the cost of achievable precision. The study focuses on improving the resolution and surface quality achievable by a low-cost hobbyist grade resin printer by integration a fiber optic taper (FOT) to get high quality optical surfaces. The modified technique has been evaluated for the achievable resolution, feature size and surface roughness. Compared to conventional resin printing, a 2.3x resolution enhancement and a surface roughness improvement of >90% has been obtained for the system tested in this work. The ability of improved printing strategy to produce optical components have been validated with 4 the fabrication of a Fresnel Lens, which is characterized for a focal spot with 1/e2 width of 3.85 µm. The study then investigates an approach to realize self-aligning optical fiber coupling system using TPL. Femtosecond laser enabled TPL has an upper hand compared to other 3D printing techniques. This method uses a point-by-point exposure and can produce optical parts with ultra-high precision and nanoscale surface roughness. As it is a point-by-point exposure, print time rapidly increases with increase in the structure dimension. This printing technique is used to create a micron-scale lens combined with a self-aligning socket for attachment to optical fibers. The study concentrates on the fabrication strategies for realization of lenses with a focus on quality and a rigid socket structure with a focus on fabrication time in a single step so that the alignment offset during fiber attachment can be minimized. The fabricated samples were characterized by slotting in single mode fiber and achieving beam focusing with the attached lens and comparing with the simulated results. Finally, the thesis explores the possibility to print optically opaque structures by a selective over-exposure technique. Conventional techniques for creating opaque structures involve usage of black ink. This study investigates the possibilities to utilize TPL to create a fully 3D printed opaque structure. In this process, the resin in selected areas of the designed structure is exposed to a higher dose. Due to this over-exposure, the material damages. The results show that this selective over exposure creates a black surface while retaining the transparency of the remaining structure. The transmittance of such burnt structures have been measured to be less than 15%. Various test patterns are demonstrated to analyze the capability of this printing process. Using the developed technique, we fabricated an absorptive shell to achieve a contrast of 24% for an imaging lens which by itself exhibited an 8% contrast.