Determination of optical nonlinearities and carrier lifetime in ZnO

Abstract

Bound-electronic and free-carrier optical nonlinearities and relaxation of two-photon-excited free carriers in ZnO have been investigated by use of a single-beam Z-scan technique at 532 nm. Under pulsed radiation of 25-ps duration, the two-photon absorption coefficient, the bound-electron nonlinear refractive index, and the change in the refractive index due to the two-photon generation of an electron-hole pair are determined to be 4.2 ± 0.9 cm/GW, -(0.9 ± 0.3) × 10-14 cm2/W, and -(1.1 ± 0.3) × 10-21 cm3, respectively. With these values in the Z scans conducted with 7-ns laser pulses, the carrier recombination time and the free-carrier absorption cross section are extracted as 2.8 ± 0.6 ns and (6.5 ± 0.9) × 10-18 cm2, respectively. © 1997 Optical Society of America.