Compact four-channel terahertz demultiplexer based on directional coupling photonic crystal

•We propose an approach to separate efficiently four frequencies terahertz waves based on three cascaded directional coupling photonic crystal waveguides.•The designed terahertz wavelength demultiplexer can split four different wavelengths of terahertz wave into different propagation directions with high transmittance and low crosstalk.•The present device is very compact and the total size is 6.8×10.6 mm2.

Electromagnetic polarization conveys valuable information for signal processing. Manipulation of terahertz wavelength demultiplexer exhibits tremendous potential in developing application of terahertz science and technology. We propose an approach to separate efficiently four frequencies terahertz waves based on three cascaded directional coupling two-dimensional photonic crystal waveguides. Both plane wave expansion method and finite-difference time-domain method are used to calculate and analyze the characteristics of the proposed device. The simulation results show that the designed terahertz wavelength demultiplexer can split four different wavelengths of terahertz wave into different propagation directions with high transmittance and low crosstalk. The present device is very compact and the total size is 6.8×10.6 mm2. This enables the terahertz wavelength demultiplexer to be used in terahertz wave system and terahertz wave integrated circuit fields.