Nonlinear Optical Properties of ZnO

摘要

Recent advances in material science have led to the production of high quality crystals for II-VI and HI-V semiconductors. Among the many II-VI semiconductors available, zinc oxide (ZnO) has attractive properties, such as a wide band gap (3.37 eV) and a large exciton binding energy (60 meV).'However, compared to the linear optical properties, there is less understanding of the nonlinear optical properties of ZnO. Some studies of the nonlinear optical responses, such as second-harmonic generation (SHG) and third-harmonic generation (THG), have been reported. The nonlinear optical responses supply a deep penetration depth of the probe beam because long excitation wavelengths can be used in two-photon absorption (2PA) and three-photon absorption (3PA). Despite the importance of competition between harmonic generation (SHG and THG) and multiphoton absorption (2PA and 3PA) for potential applications, there are only a few reports on the simultaneous measurements of harmonic generation and multiphoton absorption. In this Note, the nonlinear optical properties of ZnO were examined by nonresonant optical excitation of femtosecond pulses, which revealed concurrent harmonic generation and multiphoton absorption.