Ultrafast Multilevel Optical Tuning with CSb2Te3 Thin Films

Tunable and reconfigurable functionalities are crucial for advanced photonic devices. In this study, CSb2Te3 is proposed as a new optical tuning material. Single-shot picosecond laser pulses are used to transform the CSb2Te3 into six different optical states; each optical state can be achieved from any other state. The dielectric function for each optical state is unique and the switching is achieved on a picosecond time scale. The impact of the crystal structure on the optical tuning mechanism is studied using transmission electron microscopy and density functional theory. Second harmonic generation in the CSb2Te3 films indicates that the crystal orientation for the switched layer is influenced by the pump laser polarization. Thus electric field may provide a further degree of freedom to design phase change materials.