Highly ordered ZnO nanohole arrays: Fabrication and enhanced two-photon absorption

Highly ordered ZnO nanohole array was synthesized using pulsed laser deposition technique on the prepared template substrate fabricated by nanosphere lithography and reactive ion etching. The linear absorption coefficient around 400 nm of the nanohole array shows a significant increase compared with the corresponding value at 800 nm. The nonlinear absorption properties were investigated by Z-scan method with a femtosecond laser at the wavelength of 800 nm. An obvious enhancement of two-photon absorption is observed and the value is estimated to be 180 cm/GW, which is about 60 times larger than that of ZnO film fabricated under the same conditions. It indicates that the ordered ZnO nanohole array with enhanced two-photon absorption coefficient has a potential application in nonlinear optical devices.