Dielectric function dynamics during femtosecond laser excitation of bulk ZnO

Abstract:

Using a broadband dual-angle pump-probe reflectometry technique, we obtained the ultrafast dielectric function dynamics of bulk ZnO under femtosecond laser excitation. We determined that multiphoton absorption of the 800-nm femtosecond-laser excitation creates a large population of excited carriers with excess energy. Screening of the Coulomb interaction by the excited free carriers, causes damping of the exciton resonance and renormalization of the bandgap, causing broadband (2.33.5 eV) changes in the dielectric function of ZnO. From the dielectric function, many transient material properties, such as the index of refraction of ZnO under excitation, can be determined to optimize ZnO-based devices.