Light-harvesting structures in natural photosynthetic organelles, such as those in purple bacteria, consist of light-responsive chromophores in densely packed antennae systems with organized nanostructures. Inspired by these biological systems, we've created organic materials with densely packed J-aggregates in a polymeric matrix, mimicking the optical role of a protein scaffold. These materials exhibit tunable polaritonic properties from visible to infrared. Drawing from the structure of light-harvesting complexes in purple bacteria, we've studied interactions between light and J-aggregate-based nanorings. Electromagnetic simulations show these nanorings act as resonators, confining light beyond subwavelength scales. These findings enable bio-inspired building components for metamaterials spanning the visible to infrared spectrum in an all-organic platform, offering a fresh perspective on nanoscale light-matter interactions in densely packed organic materials in biological organisms, including photosynthetic organelles.
So-called ‘iridoplasts’ found in certain species of the genus Begonia are alike to common chloroplasts found in most plants, but with a modified, periodic internal structure reminiscent of a 1D photonic crystal. Modelling indicates that this structure gives the Begonias their iridescent blue leaves, while also enhancing the absorption of photosynthetically active radiation.
We will present an overview of the nano-optical theory underlying the model of iridoplasts, contrasting the design goals and constraints of biological and artificial systems. We use a simplified optical model based on Lorentz oscillators to answer the question of if the measured structure parameters of the iridoplasts are photonically optimised or if they reflect other biological constraints. Our results show that optimised photonic absorbers will not necessarily have high reflectance, raising the possibility that photonic structures for light harvesting in nature are more common than previously believed.
We determine the propagation loss of GaAs photonic crystal waveguides by spectral imaging of the spontaneous emission from the embedded InAs/GaAs quantum dots. The results are compared with the loss obtained by imaging the near field of the out-of-plane radiation of the waveguide mode propagating within the light cone. From the corresponding far field, we furthermore measure the mode wavevector, from which we determine the waveguide dispersion. Additionally, we show that spectral imaging allows to determine the relative efficiencies of the couplers. Using the same experiment, and detailed photonic simulations, we have determined the beta factor and the directionality of the emission of the QDs, finding beta factors up to 99% and high directionalities.
By performing a full analysis of the projected local density of states (LDOS) in a photonic crystal waveguide, we show that phase plays a crucial role in the symmetry of the light-matter interaction. By considering a quantum dot (QD) spin coupled to a photonic crystal waveguide (PCW) mode, we demonstrate that the light-matter interaction can be asymmetric, leading to unidirectional emission and a deterministic entangled photon source. Further we show that understanding the phase associated with both the LDOS and the QD spin is essential for a range of devices that can be realized with a QD in a PCW. We also show how suppression of quantum interference prevents dipole induced reflection in the waveguide, and highlight a fundamental breakdown of the semiclassical dipole approximation for describing light-matter interactions in these spin dependent systems.
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