Mid-infrared Photophysics of Boron Nitride Nanotubes

Boron nitride nanotubes (BNNTs) represent ideal substrates for first principles understanding of phonon polaritons (PhPs) due to their one-dimensional nature, tunable sizes and ready synthetic techniques. Herein, we present work towards a comprehensive understanding of their photophysical properties within the Upper Reststrahlhan Band (~1360 – 1530 cm-1). Synthetic methods towards chemical vapor deposition (CVD) growth of BNNTs and hierarchical 2D BNNT structures are presented. The ability to characterize BNNTs using a novel broadband infrared source is addressed as well as computational modeling for the reflection of a polariton wave at a strong, internal dielectric barrier. Work showing the modification of the dielectric function and subsequent polariton dispersion by the internal void within BNNTs is demonstrated, culminating in understanding of the large geometry-mediated scattering enhancement at the ε = −1 crossing of the dielectric function. Conditions that result in strongly resonant PhPs are examined in tubes which support Fabry-Perot behavior. Finally, next steps are discussed in the field of BNNT polaritonics including perspectives on future devices.Ph.D