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 TiO2 and SiO2, 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 degrees C. When the defect layer is replaced by Bi4Ge3O12, 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. (C) 2011 Elsevier B.V. All rights reserved.