Abstract
A certain class of photonic crystals with conical dispersion is known to behave as isotropic zero-refractive-index medium. However, the discrete building blocks in such photonic crystals are limited to construct multidirectional devices, even for high-symmetric photonic crystals. Here, we show multidirectional emission from low-symmetric photonic crystals with semi-Dirac dispersion at the zone center. We demonstrate that such low-symmetric photonic crystal can be considered as an effective anisotropic zero-refractive-index medium, as long as there is only one propagation mode near Dirac frequency. Four kinds of Dirac multidirectional emitters are achieved with the channel numbers of five, seven, eleven, and thirteen, respectively. Spatial power combination for such kind of Dirac directional emitter is also verified even when multiple sources are randomly placed in the anisotropic zero-refractive-index photonic crystal.
Highlights
Found in rhombic photonic crystals when the radii of the rods are fixed at two slightly different values
We proposed a kind of low-symmetric photonic crystals with conical dispersion only along the C2v symmetry axis
Spatial power combination for multidirectional emission can be observed even when multiple sources are in random positions of the anisotropic zero-refractive-index photonic crystal
Summary
Found in rhombic photonic crystals when the radii of the rods are fixed at two slightly different values. This semi-Dirac point, along with single-mode character near the Dirac frequency, ensures the existence of anisotropic zero-refractive index.
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