Title : Polaritonic excitations in non-ideal lattices of coupled microcavities containing quantum dots
The advent of optoelectronic devices utilizing various recent advances in photonics such as the harvesting of light by nanophotonic waveguides or quantum information processing has elevated the importance of the correct theoretical understanding of nanocrystalline photonic structures. Recently, a considerable interest has been drawn to crystalline structures known as Lieb lattices. Strong confinement of light in photonic Lieb lattices opens up routes to development of new light-trapping schemes. Among the problems raised by fabrication of novel nanocomposite materials (used as sources of coherent radiation) and by construction of corresponding devices one encounters the necessity of an adequate description of the so-called polaritonic crystals. The latter constitute a special class of photonic crystals featured by a strong coupling between quantum excitations (excitons) and optical fields. Investigations into polaritonic structures have given rise to polaritonics as a separate branch of photonics.Examples of polariton structures are a spatially periodic system of coupled micro-cavities (resonators), as well as arrays of quantum dots embedded in photonic nanostructures. Recently, there has been a growing interest in optical modes in microcavity lattices with embedded quantum dots. In particular, the authors of this work considered an imperfect photonic crystal, which is a lattice of tunnel-coupled microcavities (resonators) containing atomic nanoclusters (quantum dots). The achievement of a strong connection between a quantum dot and such a microresonator was demonstrated.The report is devoted to elucidation of the effect of point-like defects on polaritonic excitations dispersion in a 1D array of microcavities (resonators) with embedded one-level quantum dots. It is shown that the presence of vacancies in the microcavity lattice and atomic (quantum dots) subsystems results in a substantial renormalization of polariton spectrum and thus in a considerable alteration of optical properties of the structure. Introduction of defects leads to an increase in the effective masses of polaritons and hence to a decrease of their group velocity. Our model is primarily based on the virtual crystal approximation, which is often employed to examine quasiparticle excitations in sufficiently simple disordered superstructures. More complex systems usually require the use of more sophisticated methods such as the (one- or multinode) coherent potential approximation, the averaged T-matrix method and their various modifications.The obtained numerical results help to obtain new composite polariton structures and expand the prospects for their use in the construction of solid-state devices with controlled propagation of electromagnetic excitations.
Audience Take Away Notes :
- The result presented in the paper is of interest to both researchers and teachers, since it introduces the audience to a new section of photonics – polaritonics.
- The work introduces the audience to the use of numerical simulation of polariton dispersion based on the virtual crystal approximation
- Among the problems raised by fabrication of novel nanocomposite materials (used as sources of coherent radiation) and by construction of corresponding devices one encounters the necessity of an adequate description of the so-called polaritonic crystals.
- The obtained results help to obtain new composite polariton structures and expand the prospects for their use in the construction of solid-state devices with controlled propagation of electromagnetic excitations.