3D Printed Horn Coupler for Hybrid Photonic Crystal THz Waveguides

We present a terahertz horn coupler to enhance the coupling efficiency from a free-space wave into and out of a hybrid photonic crystal waveguide. The optimized horn structure could ideally offer 84.5% coupling efficiency of free-space radiation into a tightly confined photonic crystal waveguide mode in the frequency range of 0.359-0.430 THz. The horn coupler enables adiabatic mode-matching and is fabricated using 3D printing and gold sputtering. The proposed horn coupler could be applied for terahertz chip integrations.