Spatiotemporal refraction of light in an epsilon-near-zero indium tin oxide layer: frequency shifting effects arising from interfaces

When light travels through a medium in which the refractive index is rapidly changing with time, will undergo shift its frequency. Large frequency shifting effects have recently been reported for transparent conductive oxides. These observations interpreted as emerging from temporal changes to propagation phase bulk resulting variations index, an effect referred refraction. Here, we show that epsilon-near-zero (ENZ) layer made of indium tin oxide (ITO) originates not only this response, but includes significant spatial boundary conditions. This can lead dominant opposing certain angles. Hence, process gives rise be tailored angle incidence, decoupling amplitude and modulation.