Diplexer for terahertz-wave integrated circuit using a photonic-crystal slab

We design a compact diplexer by using a silicon photonic-crystal directional coupler having a length that is comparable to the wavelength for terahertz-wave communication integrated circuits. We experimentally demonstrate gigabit frequency-division communication in the 0.32-THz band by using a wavelength-scale (~1-mm length) diplexer.