Nanofabrication of Active Nanophotonic Materials and Architectures

Reese, Thaddeus Allen

doi:https://doi.org/10.21985/n2-gkav-ck47

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Nanofabrication of Active Nanophotonic Materials and Architectures

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Ordered arrays of metallic nanoparticles (NPs) are a promising platform for technological applications and fundamental investigations due to their ability to excite surface lattice resonances (SLRs). SLRs can support extremely high local electric fields that have been used to realize exotic physical phenomena. The open cavity architecture lends itself to the design of active devices that can achieve different responses based on environment and stimuli. However, the desire to expand to new plasmonic materials and multi-functional nanostructures while maintaining mass-production optionality requires the development of precise, yet flexible, parallel nanofabrication techniques. This thesis describes new methods to fabricate active nanostructures and the characterization of their properties. First, I demonstrate a parallel nanofabrication technique for generating partially filled and multi-metallic NP arrays. By integrating the arrays with gain media, I found that partially filled arrays (as low as 10%) could act as cavities to achieve active lasing action. The flexible process flow was then used to generate bi-metallic arrays that could support bi-modal lasing simultaneously, as well as tri-metallic arrays that could support three SLRs with wavelengths separated by hundreds of nanometers. In a separate project, I produced titanium nitride NP arrays that could support dipolar or quadrupolar SLRs at near-infrared wavelengths. By characterizing their ultrafast optical properties, I found SLRs had distinct photoinduced transmission from localized surface plasmons. These trends persisted under extremely high fluence conditions. Finally, I developed a procedure to fabricate protein hydrogel structures that spontaneously formed nanoscale patterns over large areas from microscale masks. By tuning the concentration of the initial protein solution, I could decrease line features to length scales relevant to photonic applications. This work lays the foundation for ordered plasmonic structures that can dynamically modulate their SLR wavelength by introduction of different ionic species. The scalable techniques described in this thesis can be easily adapted to new materials of interest, and future developments in the field of active plasmonics. I expect these methods to be useful for applied optical technologies, as well as fundamental studies of nanophotonics.

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