Structural Color And Photonic Crystals Based On Phase Change Materials And Their Electrical Control

Phase change materials(PCM)usually have stable crystalline and amorphous states,and have been widely studied and applied in many fields due to the huge differences in optical and electrical properties between different phases,such as rewritable optical discs,phase change memory,etc.In recent years,there have been more and more researches on tunable optical devices based on phase change materials.People hope that phase change materials can be used as an adjustable,nonvolatile,and flexible carrier to achieve more optical functions.And this article has done some research based on PCM with three aspects:tunable thin-film interference structural colors,tunable photonic crystals and electrical control of phase change thin films.1.Tunable thin-film interference structural colors based on phase change materialsStructural color is the result of the interaction between micro-nano structure and light.If the structural color can be tuned dynamically,then it can be applied in many applications such as display,spatial light modulation and other functions.In this article,we fabricated thin film interference structure based on phase change material Ge₂Sb₂Te₅,and observed the color modulation effect when we change the phase state of the PCM.Then we preliminarily studied the effect of the film thickness on the structural color.Then the strong interference structure based on the phase-change material Sb₂S₃ film is further proposed.Experiments and theories prove that the structural color produced by this structure is independent with the incident angle.So the strong interference structure is more suitable in applications such as display etc.2.Tunable photonic crystals based on phase change materialsFor traditional photonic crystal,the photonic band gap is fixed and cannot be adjusted after it fabricated.If the photonic band gap can be adjusted dynamically and quickly through external stimuli,then this adjustable band gap will allow people to control light more flexibly and efficiently.So in this paper,we combined the phase change material with the photonic crystal,and proposed the concept of a tunable photonic band gap photonic crystal based on the phase change material.Through calculations and experiments,a simple exploration of one-dimensional and two-dimensional photonic crystals based on phase change materials is done.Both simulations and experiments show that the change of the phase state can significantly change the width and position of the photonic band gap.This change in the band gap can determine whether the corresponding frequency light can be transmitted in the photonic crystal.Furthermore,we also briefly explained that the tunable photonic crystal based on phase change materials can be applied to optical switches and other devices.3.Research on electrical control of phase change thin filmsThe successful industrialization of many applications of phase-change materials in the optical field,such as phase-change displays,greatly depends on whether a large-area phase-change film can be efficiently controlled by electrical means.The realization of the tunable interference structure color based on PCM and the tunable band gap photonic crystal based on PCM that we have studied before also depends on the efficient electrical control of the phase change film.Therefore,in this article,we have explored the electrical phase switching properties of ultra-thin phase change films through experiments.There are two ways to electrically tune the phase of PCM.One way is let the current pass directly through the phase change material like cross-bar phase-change memory cell.Another way is use lateral microheater structure.The crossbar structure and the lateral microheater structure device were fabricated through experiments,and experiments found that the lateral microheater structure is a more effective way to tune the phase states of phase change thin films.On the basis of continuous improvement of the device structure,we have achieved effective electrical control of a large area of ultra-thin phase change film.