Steering of beam trajectory by distorted photonic crystals

Abstract: Electromagnetic waves follow linear paths in homogenous index media, with the exception of band edges. In this study, we introduced spatially distorted photonic crystals (D-PCs) that are capable of beam-steering light waves, even when a homogeneous refractive index is maintained. We analyzed their equifrequency contours to investigate the correspondence between the direction of distortion and the direction of the group velocity vector in the D-PC. Thereafter, we experimentally verified the beam-steering phenomenon in the terahertz range using an all-silicon D-PC. Our structures serve as on-chip beam trajectory control without the need for any specially-engineered materials, using only lattice distortion.