Abstract

Although high-power lasers have enabled great development in two-photon absorption (TPA) spectroscopy in the excitonic region, little work has been done to examine carefully the nature of interband transitions (allowed-allowed or allowed-for- bidden) when the excitation energy 2ℏω is varied. To analyze this problem two different materials were considered: ZnO with a direct gap (E_g = 3.43 eV) and AgCI with an indirect one (E_gl = 3.2 eV), and the nonlinear luminescence technique was used to study the TPA spectral dependence (at 77 K) near and far from the energy gap.

© 1986 Optical Society of America