Compact terahertz photonic crystal chip sandwiched in parallel metallic plates

Broadband, low-loss, low-dispersion propagation of terahertz pulses in compact waveguide chips is indispensable for an integrated terahertz system-on-chip. Conventional two-dimensional photonic crystal (PC) based terahertz waveguides are either all-metallic or all-dielectric, having either high propagation losses due to the Ohmic loss of metal, or a narrow transmission bandwidth restricted by the range of single-mode operation in a frequency range defined by the PC bandgap, respectively. Here, we present a hybrid (metal/dielectric) on-chip terahertz waveguide, in which the guided mode is completely confined by parallel gold plates and silicon PCs in vertical and lateral directions, respectively. Based on theoretical and experimental investigations, we demonstrate that the hybrid waveguide supports a single-mode, wide-band transmission over 0.367-0.411 THz (bandwidth of 44 GHz) with low loss (less than 0.05 dB/mm) and low group velocity dispersion (from -8.4 ps/THz/mm to -0.8 ps/THz/mm). This work enables more compact, wideband, on-chip terahertz waveguides and auxiliary functional components towards future ultra-high-density integrated terahertz devices in particular in the field of wireless communications.