Study of Multilayer Ceramic Photonic Crystals in THz Region

We have fabricated one-dimensional photonic crystals with a conventional ceramic layering process and investigated their terahertz wave transmission properties by terahertz time-domain spectroscopy (THz-TDS). In one-dimensional photonic crystals with a structural defect, a narrow transmission band (i.e., a defect mode) appears within the band gap. However, the dielectric losses of the ceramic materials significantly suppress the transmission intensity of the defect mode. The observed low transmission is mainly associated with the absorption loss of the defect layer material. Since the internal multiple reflections enhance the absorption loss, tuning the periodicity of the photonic crystal from a high reflectivity condition is effective for improving the transmission intensity of the defect mode. The measured highest peak transmission is -4.5 dB when periodicity is changed from a quarter-wavelength stack.