Investigation of Low-Index Waveguiding in Inverse Rod-Connected Diamond Photonic Crystals

In 2D photonic crystal waveguide designs, in-plane guidance is achieved through total internal reflectance and low loss guides are made of a higher refractive index than the surrounding medium, while losses from out-off plane scattering restrict the finesse (or Q-factor) achievable in cavity structures. In contrast, 3D photonic crystals can provide confinement in all directions due to their complete photonic band-gap (PBG)[1,2] potentially providing lower loss structured waveguides[3], low radius bends, full 3D circuits and higher Q-factor cavities. Here we investigate such waveguides in 3D crystals, in particular the 3D direct rod-connected diamond (RCD) photonic crystals (PhCs)[4-9]. We exploit the similarity of the Γ-L plane in a 2D hexagonal crystal slab and the inverse RCD crystal to transfer existing waveguide designs from 2D to 3D.