Generation of Tamm Plasmon Resonances for Light Confinement Applications in Narrowband Gradient-Index Filters Based on Nanoporous Anodic Alumina

Gold-coated gradient-index filters based on nano-porous anodic alumina (Au-coated NAA-GIFs) were used as model platforms to elucidate how Tamm plasmons can be tailored by engineering the geometric features of the plasmonic and photonic components of these hybrid structures. NAA-GIFs with well-resolved, intense photonic stopbands at two positions of the visible spectrum were fabricated through sinusoidal pulse anodization. These model photonic crystals were used to assess how the quality of Tamm plasmon resonances can be enhanced by tuning the features of the dielectric mirror and the thickness of the porous gold coating layer. It is found that the highest value of the quality factor of Tamm resonance (QTamm = 237) is obtained for 11 nm of gold on a dielectric mirror with low porosity corresponding to the resonant spectral position of lambda Tamm of similar to 698 nm. Our analysis indicates that Tamm resonances in as-produced Au-coated NAA-GIFs are weak due to the constrained range of wavelengths (narrow bands) at which these photonic crystal structures reflect light. However, after broadening of their photonic stopband upon pore widening, Tamm resonances become better resolved, with higher intensity. It is also observed that the quality of light confinement worsens progressively with the thickness of the porous gold coating layer after a critical value. In contrast to conventional surface plasmon resonance systems, this hybrid Tamm porous system does not require complex coupling systems and provides a nanoporous structure that can be readily tailored for a range of photonic technologies such as sensing and lasing.

Automated summary

Gold-coated gradient-index filters based on nano-porous anodic alumina were studied to investigate the properties and applications of Tamm plasmons. The quality factor of Tamm resonance can be improved by tuning the features of the dielectric mirror and the thickness of the porous gold coating layer. The Tamm resonances in Au-coated NAA-GIFs are weak due to the narrow bands of the photonic crystal structures, but become better resolved and more intense after broadening of the photonic stopband. The hybrid Tamm porous system provides a nanoporous structure that can be readily tailored for various photonic technologies.