Date of Award
Doctor of Philosophy (PhD)
Electrical, Computer & Energy Engineering
Robert R. McLeod
Photonic devices increasingly require three dimensional (3D) control of refractive index, but existing fabrication methods such as femtosecond micromachining, multi-layer planar lithography and bulk diffusion can only address a select scale range, are often limited in complexity or thickness and have low throughput. This Thesis presents a new fabrication process, liquid deposition photolithography (LDP), that can efficiently create mm3 optical devices with programmable, gradient index of refraction with arbitrary feature size. Index contrast of 0.1 is demonstrated, which is 100 times larger than femtosecond micromachining and 20 times larger than commercial holographic photopolymers, allowing greater flexibility in photonic device fabrication.
The 3D volume is created through repetitive layering of liquid photopolymer, where each layer is structured and solidified by projection lithography. In addition to full 3D control of index, processing time in LDP is reduced compared to multi-layer planar lithography because the material is self-developing, enabling the entire process to be completed on a single instrument. The self-developing process has the unusual property that total fabrication time for a fixed thickness decreases as the number of layers is increased, enabling fabrication 105 faster than femtosecond micromachining. The high throughput and index contrast is demonstrated by sequentially writing 100 layers to fabricate a mm thick waveguide array that has a fabrication rate of 1.2 mm3/hour and index contrast of 0.1.
Urness, Adam C., "Liquid Deposition Photolithography for Efficient Three Dimensional Structuring" (2013). Electrical, Computer & Energy Engineering Graduate Theses & Dissertations. 64.