Thermally tuning of the photonic band gap of SiO₂ colloid-crystal infilled with ferroelectric BaTiO₃

SiO₂ colloid crystal infilled with BaTiO₃ was synthesized by a process of self-assembly in combination of a sol-gel technique. It is found that infilling of the fully crystallized BaTiO₃ into the colloid assembly can enhance the photonic band gap significantly. In the vicinity of the ferroelectric phase transition point of BaTiO₃ (100-150°C), the photonic band gap of the assembly exhibits a strong temperature dependence. At the Curie point, the band gap has a 20 nm redshift, and the optical transmittance reaches its minimum. Such a temperature-tuning effect in the photonic band gap should be of high interest in device applications.