Two-beam coupling by a hot electron nonlinearity

Transparent conductive oxides such as indium tin oxide (ITO) bear the potential to deliver efficient all-optical functionality due their record-breaking optical nonlinearity at epsilon near zero (ENZ) wavelengths. All-optical applications generally involve more than one beam, but, our knowledge, coherent interaction between beams has not previously been discussed in these materials, which have a hot electron nonlinearity. Here we study ENZ ITO and show that spatial temporal interference important consequences two-beam geometry. Our pump–probe results reveal polarization-dependent transient is explained by diffraction of pump light into probe direction temperature grating produced interference. We further this effect allows tailoring tuning frequency or chirp. Having fine control over strong ultrafast may enable neural networks, nanophotonics, spectroscopy.