Applications of nanoimprint lithography to nano-photonics

This thesis work presents the further development of nanoimprint lithography (NIL) and its application to nano-photonics.; The objective of the thesis is to use nanoimprint lithography to address the specific needs of nano-photonics. It was our intention to first develop a low-cost, high throughput fabrication technique capable of continuous nanoscale patterning; and second, to further explore nanoimprint lithography processes for producing devices with high performance and low cost.; The thesis is divided into 7 chapters. Chapter 1 is an introduction to the field of nano-photonics and states its challenges and possible solutions. Chapter 2 presents a new concept, roller nanoimprint lithography, for continuous nano-patterning. Two generations of roller imprint machines are designed and tested. Three different methods for roller imprinting are successfully developed. In chapter 3, field emitter arrays with a high packing density of 4.4 × 1013/m2 are successfully fabricated using nanoimprint lithography. Chapter 4 demonstrates the direct nano-patterning of sol-gel, precursors of ceramic materials, by nanoimprint lithography. Grating patterns with 300-nm pitch and various waveguide gratings with μm-scale pitches are imprinted with smooth profiles. Chapter 5 discusses the alignment of liquid crystals using nano-imprinted gratings. Gratings with 200 nm, 300 nm, 3.8 μm and 50 μm periods are fabricated by NIL and used to align nematic liquid crystals. A comparison shows that smaller gratings align liquid crystals better. A grating aligned liquid crystal light valve is fabricated and characterized optically. Alignment of liquid crystals using a directly imprinted sol-gel grating of 300 nm period is demonstrated as well. In Chapter 6, tunable optical filters using a subwavelength resonant grating and a liquid crystal cladding layer are successfully fabricated. The present tuning range is 17 nm. Device concept, performance and parameters are discussed in detail. The tunable optical filter is applied as the feedback mirror of an external cavity single mode tunable laser. The laser has 7 nm tuning range and better than 30 dB side mode suppression ratio. Finally, Chapter 7 discusses future research.