Photo-induced THz response of VO2 under high pressures

We apply ultrafast optical pump – THz probe spectroscopy in order to investigate the nature of the high pressure metallic state of VO2 single crystal. The pump excitation was performed using near-infrared pulses at the wavelength of 800 nm. The probe pulses with a frequency of 30 THz were generated by difference frequency mixing and focused on the sample mounted inside a diamond anvil pressure cell. Using the probe photon energy far below the bandgap of VO2 we were able to explore the response of free charge carriers near the Fermi level.