Two-dimensional Tunable Bandgap Photonic Crystals Based On VO₂ Phase Transition

Vanadium dioxide (VO₂) is a special phase transition functional material, which can undergo a first order transition from insulating phase to metallic phase by thermal excitation or electron injection. Accompanied with the metal-insulator transition (MIT) are abrupt changes in its electrical and optical properties. These characteristics make VO₂ a promising material for a wide variety of technological applications, such as infrared detect, optical storage, optical communication.Firstly, high quality VO₂ thin films are deposited on different substrates by reactive direct current magnetron sputtering. The composition and microstructure of VO₂ thin film is characterized by X-ray diffractometer (XRD) and high resolution transmission electron microscopy (HRTEM).Secondly, based on the changes of optical properties during VO₂ phase transition, the thesis comes up with two-dimensional (2D) tunable bandgap photonic crystals. The 2D VO₂ tunable bandgap photonic crystals are designed and simulated by Rsoft7.0 software. Through the software, the dispersion curves of insulating phase and metallic phase are simulated and two different photonic crystal structures, hexagonal structure and square structure, are designed. The bandgaps of photonic crystals are calculated separately under VO₂ in insulating phase and metallic phase, the result of simulation indicates the bandgaps of photonic crystals are tunable during VO₂ phase transition. The structure parameters of photonic crystals are optimized based on the specific fabrication process, and an optical mask is designed by fabricating photonic crystals.Finally, 2D tunable photonic crystals based on VO₂ phase transition are fabricated by lithograph and dry etching process. Scanning electron microscopy (SEM) is used to characterize the surface morphology of photonic crystals, the fabrication of photonic crystals are ideal. The photonic crystals are tested simply by Fourier transform infrared spectroscopy (FTIR) and terahertz time-domain spectrometer, the bandgaps of photonic crystals are not analyzed through the transmission spectrums of photonic crystals, other tests will be carried out.