摘要
Vanadium dioxide (VO2), a representative phase-transition material, exhibits nonlinear optical responses during its transition from an insulating to a metallic state. By investigating the transient photoresponses of a VO2 thin film at different temperatures, additional slow-growth and hybrid phases are discovered between the insulating phase at low-temperature and metallic phase at high-temperature. The amplitude of the VO2 photoresponse at 68 degrees C in the slow-growth phase is observed to be 5.5 times greater than that at room temperature. The controllability of relaxation time is also demonstrated from a few tens of picoseconds to a few nanoseconds. The optimized conditions for all-optical modulation applications are explored.