Emulation of the Graphene structure using photonics

• Applicant: Professor Alexander Szameit, Ph.D.
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 270107438

In this proposal, we will emulate the physics of graphene using optical waveguide arrays that are arranged in honeycomb geometry. Since the paraxial wave equation (which describes the propagation of light through the waveguide array) is mathematically equivalent to the Schrödinger equation (describing the time-evolution of electrons in graphene), the dynamics of a propagating light wave in a periodic refractive index modulation (a waveguide array) will be similar to the evolution of an electronic wave function in the crystalline potential of a solid. In this vein, in an array of waveguides that are arranged in honeycomb geometry, it is possible to directly observe graphene wave dynamics using classical light waves. Particular benefits of using such photonic graphene are: (1) that the edges of electronic graphene tend to be very irregular and contaminated with adsorbates, whereas the use of optical structures to probe these edges provides a natural advantage; (2) that even strongest homogeneous and inhomogeneous strain can be applied to photonic graphene during the fabrication process without damaging the bonds between the single lattice elements; and (3) the possibility to analyze composite disorder (caused by impurities in the periodic lattice) and structural disorder (due to random lateral shifts of the lattice sites) independently of each other and without any correlations, in contrast to conventional graphene, where both disorder types appear simultaneously and in a correlated fashion.By exploiting the analogy between the evolution of electrons in graphene and the propagation of photons in honeycomb photonic structures, we will fabricate novel photonic devices with unprecedented properties, lay the theoretical foundation for their description and understanding, and transfer the results to graphene, where possible. Taking advantage of the ease of fabrication of optical graphene devices, we will not be limited to perfect honeycomb lattices, but we will use experimental techniques to induce strain, compression, and disorder in a controllable fashion, in order to induce new functionalities to the devices. We will exploit the impact of strain and disorder on the graphene structure, we will probe new states inaccessible to conventional graphene, and we will control the existence of these states in the fabricated structures. In the field of solid state physics and materials science, we will be able to explore phenomena which are much easier to demonstrate and study in honeycomb photonic structures than in graphene itself. However, these findings will be associated with the honeycomb structure and Dirac dispersion relation that the two class of materials share. In this vein, a full understanding of the implications of the unique geometry of graphene will facilitate the refinement of existing devices based on graphene as well as the development of new ideas and concepts for applications in various fields.

• DFG Programme: Research Grants