Temperature dependence of defect mode in a defective photonic crystal

The temperature dependence of the defect mode in a one-dimensional defective photonic crystal is studied by simultaneously considering thermal expansion effect and thermal-optical effect. As the thickness and index of refraction of each constituent layer are modulated by temperature, the defect mode can be shifted as a function of temperature and thus a tunable transmission filter working in the visible region is proposed. The structure is designed with TiO ₂ and SiO ₂, and the latter is also used as the defect layer. It is found that the wavelength of the transmittance peak shifts 0.37 nm for a temperature increase of 100 °C. When the defect layer is replaced by Bi ₄Ge ₃O ₁₂, the wavelength of the transmittance peak shifts can be enhanced to 0.50 nm for the same temperature increase, leading to a 35% improvement in temperature sensitivity. In addition to the tunable filtering feature in this design, it can also be used as a temperature-dependent refractometric optical sensing device.