Compact multi-channel terahertz wave demultiplexer

We numerically demonstrate a compact multichannel terahertz demultiplexer which is composed of three photonic crystal directional couplers. By using plane wave expansion, the transmittance of the designed photonic crystal directional couplers are analyzed. Then, the performance of the demultiplexer based on the photonic crystal directional couplers is investigated with the aid of finite-difference time-domain method. The transmittances at frequencies of 0.57THz, 0.52THz, 0.54THz, and 0.6THz are 98%, 92%, 94%, and 88.2%, respectively. We confirm that the device can split four different terahertz wave frequencies into different output ports with high transmittance efficiency. In addition, the total size of the our terahertz demultiplexer is about $5.2\mathbf{mm}\times 5.6\mathbf{mm}$ , which can be easily integrated in terahertz circuit systems. This advice provides a new method to manipulate terahertz wave.