Shanghai Institute of Optics and Mechanics has made progress in research on femtosecond laser induced vanadium dioxide phase transition

Recently, Wang Jun, a research team from the Optical Chip Integration Research and Development Center of Shanghai Institute of Optics and Mechanics, made progress in the femtosecond laser induced phase transition of vanadium dioxide, and the related achievements were published in Optics Express under the title of "Femtosecond laser induced phase transition in VO2 films".

The semiconductor metal phase transition in metal oxides has attracted much attention due to its scientific significance in condensed matter physics and its potential applications. Among them, vanadium dioxide is a unique material with important basic research and practical value because of its phase transition characteristics at room temperature, the phase transition induced by femtosecond laser can be triggered on the sub picosecond time scale, and has a very high response rate and significant changes in optical properties.

The research team prepared vanadium dioxide films with different thicknesses by magnetron sputtering technology. The phase transition temperature is between 330-348K, and there is an obvious thermal hysteresis loop. The optical response of vanadium dioxide thin films induced by 1040 nm femtosecond laser was studied by using a variable temperature Z-scan experimental device. At low repetition frequency (10 kHz), vanadium dioxide thin films retain the characteristics of semiconductor phase and have obvious nonlinear absorption characteristics. When the repetition rate of the pulsed laser is higher than 50 kHz, the semiconductor to metal phase transition occurs, and the nonlinear optical characteristics change from two-photon absorption to saturated absorption. In addition, the threshold value of laser induced phase transition decreases with the increase of temperature. In this case, the phase transition is mainly caused by the heat accumulation of the laser pulse. Using optical means to study the optical performance change and phase transition mechanism of vanadium dioxide induced by femtosecond laser, and realizing phase transition control of vanadium dioxide in ultrafast time scale will be beneficial to its potential applications in storage devices, ultrafast optical switches and bistable optoelectronic devices.

This work has been supported by the National Natural Science Foundation of China and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.

Fig. 1 (a) Temperature dependence of VO2 film transmittance. (b) Z-scan results of 300K, VO2 films at different laser energies.

Source: Shanghai Institute of Optics and Precision Machinery, Chinese Academy of Sciences