Space-coiled Photonic Structures for Waveshaping and Light Confinement Applications

The periodic arrangement of dielectrics in 1-D, 2-D and 3-D called as photonic crystals exhibit bandgap for electromagnetic waves, anomalous dispersion and ultra-high confinement. In this work, we realize a new photonic crystal formed by space-coiled structures. The space-coiled geometry is not only compact but also structurally anisotropic as it lacks mirror and rotational symmetries. A square lattice photonic crystal formed by such a space-coiled atom shows an elongated wavevector diagram for transverse magnetic (TM) polarization. Compared to the conventional photonic crystals, the elongated dispersion contours are useful for direction-dependent beam steering. Particularly, we found that the compactness of the coil systems brings high-frequency modes (0.81(c/a) to 0.9(c/a)) to the second band. Such high-frequency contours are usually belonging to the higher photonic bands of the conventional PhCs. This can lead to direction-dependent beam shaping and beam steering applications. The proposed space-coiled structures also strongly confine the electromagnetic mode in between the narrow-space coils. Therefore, we anticipate that the light-matter interactions and field perturbation applications can be performed at sub-wavelength length scales with the proposed space-coil structures.