Terahertz Spectroscopy of Metal-Insulator Transition in Vanadium Dioxide

Vanadium Dioxide is an attractive material for high-speed optical and electrical switching as it undergoes a metal-insulator transition near room temperature (340 K). We examine the phase transition using free-space THz transmission spectroscopy. THz probe is sensitive to the metal-to-insulator transition, because the insulating phase is transparent at THz frequencies while the metal phase is highly reflective. We demonstrate that THz transmission exhibits hysteresis of the metal-insulator transition during a temperature cycle. The phase transition gives rise to not only a reduction in transmission but also a spectral broadening as temperature increases.