14 - Fluctuation-dominated materials for advanced photonics

The aim of this project is to develop nanostructured materials that utilize optical near-field interactions and disorder-induced fluctuations of local electromagnetic fields to achieve novel photonic functionality. While Nature uses disordered nanostructured materials since millions of years, e.g., in the wings of colorful butterflies, mankind has learned only recently how to nanostructure metal to detect a single molecule. Tailoring disorder in nanostructured dielectric and metallic materials to optimize the coupling of electromagnetic fields to suitably chosen quantum emitters (laser dyes, J-aggregates, quantum dots,etc.) is mostly unchartered territory; even though recent progress in materials nanofabrication, optical spectroscopy and theoretical solid state physics provides, in principle, all necessary tools. Within this project, experts from these fields join forces to

  1. enhance local electromagnetic field fluctuations by tailoring disorder in selected quasi-two-dimensional and quasi-three-dimensional metallic and dielectric nanostructures and
  2. insert quantum emitters such that their nonlinear response yields novel photonic functionality.

Such system systems are inherently robust since environment-induced detunings between certain pairs of emitters and local cavities are compensated by other functionally equivalent pairs. The project focuses on three kinds of disordered systems:

  1. arrays of dielectric nanoneedles made of technologically relevant transparent semiconductor oxides and nitrides,
  2. percolating metal films with nano-sized voids and islands and
  3. nanoporous gold nanoparticles obtained by de-alloying Au-Ag nanoparticles.

These samples will be covered or infiltrated by optically nonlinear material. Besides designing potentially even economically attractive photonic materials, the project is expected to substantially deepen our microscopic understanding of light-matter coupling on the nanoscale, the physics underlying disorder-induced light and surface plasmon localization and - more generally - of fluctuation-dominated systems. The time structure of individual localized electromagnetic modes will be probe in a recently developed ultrafast SH microscope in Oldenburg whereas their spatial mode profile is mapped with 20-nm resolution in a new near-field microscope. The theoretical analysis of disorder-induced localization phenomena will be based on the expertise of the Ilmenau theoretical physics group for optical manifestations of Anderson localization and for coupled exciton-plasmon systems. Tailor-designed disordered samples will be provided by the Ilmenau material science group. A close interdisciplinary collaboration and continued feedback among the teams will ensure the fabrication of samples with tailor-made disorder and novel or at least superior photonic functionality.