Extraordinary permittivity modulation in zinc oxide for dynamic nanophotonics

Dynamic control over the permittivity of materials enables control over the amplitude, phase, and polarization of light. Thus, to realize practical tunable devices, it is important to perform a detailed dynamic characterization of technology-relevant materials with substantially tunable optical properties. In this work, we demonstrate extraordinarily large, unity-order permittivity modulation in zinc oxide through interband pumping. The large permittivity changes actively enable large reflectance modulation in both lithography-free mirrors (70% at 31.6 mJ/cm2 pump) and nanodisk resonators (55% at 7.6 mJ/cm2 pump fluence). The relaxation time for this response is 20 ps. We explore the physical origins of the permittivity modulation and determine the physical limits. The results of this study will advance the realization of ultrafast dynamic optical devices for optical switching, beam-steering, and spectroscopy.