Non-Perturbative High Harmonic Generation in Thin Film ITO

For decades, thin film materials made of metals or doped semiconductors have been a suitable candidate for supporting localized surface plasmon or phonon-polariton modes. More recently, the Epsilon Near Zero (ENZ) mode has been observed in subwavelength thin films. This ENZ mode is defined by the electric permittivity approaching zero, leading to an increased light-matter interaction. Thus, materials that can support the ENZ mode are highly desirable for sensitive optical measurements. Here, we show Indium Tin Oxide (ITO) as a suitable candidate for measuring high harmonic generation due to its tunability of the ENZ mode, allowing for the ENZ wavelength to be shifted over a wide range of wavelengths. These ITO thin film samples will be used to observe harmonic generation in the non-perturbative regime as well as transient harmonic generation measurements. The robust optical properties of ITO thin films suggest they can be utilized for future opto-electronic applications.