Fabrication of three-dimensional photonic crystal device for terahertz wave

We have fabricated a simple-cubic-lattice photonic crystal (PhC) device based on high-resistivity silicon in the terahertz (THz) range by micro-electro-mechanical system (MEMS) techniques. The lattice constant of the three-dimensional (3D) PhC device is 120 mu m, resulting in a photonic band gap (PBG) centered at 1 THz. The 3D PhC device was constructed by stacking ten 120-mu m-thick chips with periodic pillars and holes patterned respectively on both of their sides by Si deep reactive ion etching. By THz time-domain spectroscopy, the PBG of the device was observed between 0.83 and 1.17 THz in the Gamma-Z direction with a transmittance attenuation of about 35 dB, which is in good agreement with a numerical calculation result.