Understanding and manipulating the interaction of light with matter such as electrons, atoms, molecules, and artificially engineered materials form an important field of study in different areas such as in optoelectronics, energy technology, spectroscopy, imaging, remote sensing and communications. This thesis focuses on the emerging field of nanophotonics where light is manipulated at the nanoscale, more specifically advanced optical systems based on conducting polymers. First, we show that nanostructures of an n-type conducting polymer named poly(benzodifurandione) (PBFDO) can sustain localized surface plasmon resonances similar to metallic nanostructures. Unlike metals, however, they exhibit reversible chemical/electrical switching of their plasmonic response, with promising applications in dynamic nanophotonics. We further explore hybrid systems by integrating conducting polymer nanoantennas with a thin film of indium tin oxide (ITO), which is known as an epsilon-near-zero (ENZ) material because of having vanishing permittivity within the infrared region that enables peculiar optical properties. By designing antenna resonances to spectrally overlap with the ENZ regime of ITO, coupling is achieved, giving rise to new hybrid optical modes. The redox-tunability of the conducting polymer enables reversible modulation of this coupling. Simulations reveal that the ENZ mode is excited by the near-field of the conductive polymer nanoantennas, suggesting opportunities in nonlinear optics such as electro-tunable nonlinear refractive index. We also explored similar coupling possibilities using weaker nanoantennas, such as from PBFDO having much lower charge carrier mobility in general compared to other conducting polymers. The thesis then investigates nanoantennas made from an in-plane anisotropic material, based on uniaxially stretching a conducting polymer thin film which causes a difference in the in-plane charge carrier mobility because of partial alignment of its polymer chains. We show that nanostructures made from such films can induce optical chirality even for geometrically symmetric shapes. The chiral response could then be chemically tuned through tuning the redox-state of the polymer. This study adds a fundamentally different ultrathin dynamic design to the field of chiroptics.
Suraya Kazi (Thu,) studied this question.