Thermally tunable filter for terahertz range based on defect mode in one-dimensional photonic crystal

We demonstrate a highly tunable (up to 20%) spectral filter for the terahertz range. The filter is based on a defect mode caused by inserting a defect layer into an otherwise periodic one-dimensional photonic crystal. The high tunability of a narrow transmission band (defect mode) originates from a strong temperature dependence of the permittivity of incipient ferroelectric (KTaO/sub 3/) acting as the defect.