Title: Topology-optimized Dual-Polarization Dirac Cones,
Abstract: We apply a large-scale computational technique, known as topology
optimization, to the inverse design of photonic Dirac cones. In particular, we
report on a variety of photonic crystal geometries, realizable in simple
isotropic dielectric materials, which exhibit dual-polarization and
dual-wavelength Dirac cones. We demonstrate the flexibility of this technique
by designing photonic crystals of different symmetry types, such as ones with
four-fold and six-fold rotational symmetry, which possess Dirac cones at
different points within the Brillouin zone. The demonstrated and related
optimization techniques could open new avenues to band-structure engineering
and manipulating the propagation of light in periodic media, with possible
applications in exotic optical phenomena such as effective zero-index media and
topological photonics.