Nonlinear optical microscopy analysis of ultrafast phase transformation in vanadium dioxide

The nonlinear optical properties of solid-solid phase transformation in vanadium dioxide are studied. It is found that the efficiency of the third-harmonic optical signal generated from the surface of the material increases by 1.5 orders of magnitude as a function of this phase transformation. Microscopy studies show the hysteresis of the phase transformation on a micrometer-size scale.