Nonlinear Photoluminescence from Patterned ITO Thin Films

ITO is a transparent conductive material commonly used in everyday life and for its potential in material research. In nonlinear optics for instance, ITO has shown great capabilities for harmonic generation in its epsilon-near-zero configuration. In this article, we demonstrate a completely new nonlinear behaviour from ITO thin layers. After a Ga-Focused Ion Beam (FIB) milling of the thin film, we observe nonlinear photoluminescence produced for tightly focused femtosecond pulses. The signal shares strong similarities with that commonly detected from noble metals. We show that the arising of this nonlinear photoluminescence originates from the radiative decay of metal-like hot electron distribution in the material and is associated to a modification of the optical properties by the Ga ions.