A new type of broadband link enabling extremely high-speed chip-to-chip communication is presented. The link is composed of fully integrated sub-mmWave on-chip traveling wave power couplers and a low-cost planar dielectric waveguide. This structure is based on a differentially driven half-mode substrate integrated waveguide supporting the first higher order hybrid microstrip mode. The cross-sectional width of the coupler structure is tapered in the direction of wave propagation to increase the coupling efficiency and maintain a large coupling bandwidth while minimizing its on-die size. A rectangular dielectric waveguide, constructed from Rogers Corporation R3006 material, is codesigned with the on-chip coupler structure to minimize coupling loss. The coupling structure achieves an average insertion loss of 4.8 dB from 220 to 270 GHz, with end-to-end link measurements presented. This system provides a packaging-friendly, cost effective, and high performance planar integration solution for ultrabroadband chip-to-chip communication utilizing millimeter waves.