Zinc oxide (ZnO) has been extensively studied in the past decades because of its properties like its wide bandgap and large exciton binding energy, which make it a promising candidate for a variety of optoelectronic applications. The process of high-order harmonic generation (HHG) with its high sensitivity to the materials band structure allows for investigations of the electronic properties on the femtosecond timescale. If driven sufficiently strong, ZnO thin films show a transition from spontaneous to lasing emission. This threshold at the Mott density can be used as a measure to gain insight on the interplay of excitons and the formation of an electron-hole plasma. Here, we systematically investigate this intermediate regime between lasing and spontaneous luminescence as a function of the sample temperature by simultaneously measuring the photoluminescence and high-order harmonic spectra. The experiments were conducted on a polycrystalline ZnO thin film sample at liquid helium temperatures by irradiation with intense femtosecond mid-IR laser pulses of 3.5µm. Comparing the respective temperature and laser pulse energy dependencies, these results allow for new insights into the nonlinear optical properties and electronic dynamics in ZnO.

Investigation of the pulse energy and temperature dependence of photoluminescence and high harmonic generation from a polycrystalline thin film ZnO sample

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.