Abstract:

To obtain the adjustable photonic crystals (PCs), we numerically investigate one-dimensional (1D) PCs with alternating VO₂ and SiO₂ layers through transfer matrix method. The dispersion relation agrees well with the transmittance obtained by the finite element calculation. Tunable band gaps are achieved with the thermal stimuli of VO₂, which has two crystal structures. The monoclinic crystal structure VO₂ (R) at low temperature exhibits insulating property, and the high temperature square rutile structure VO₂ (M) presents metal state. Concretely, the bandwidth is getting narrower and red shift occurs with the higher temperature in VO₂ (R)/SiO₂ PCs structure. Based on the phase change characteristics of VO₂, we can flexibly adjust the original structure as VO₂ (R)/VO₂ (M)/SiO₂. By increasing the phase ratio of VO₂ (R) to VO₂ (M), the band gap width gradually becomes wider and blue shift occurs. The discrete layers of gradient composites on the dispersion of 1D PCs are also investigated, which enhances the feasibility in practical operation. Thus, our proposed thermal modulation PCs structure paves a new way to realize thermal tunable optical filters and sensors.

Key words: photonic crystals, VO₂, thermal modulation, phase change