Two-photon optical characteristics of zinc oxide in bulk, low dimensional and nanoforms

We report the two-photon luminescence (TPL) and second-harmonic generation (SHG) characteristics of zinc oxide (ZnO) in ceramic, thick film and nanorod. Sintering, physical vapour deposition (PVD), and hydrothermal methods were used in preparing the three forms of samples, respectively. Wide-band luminescence in the visible wavelength was observed with green/yellow emission in ceramic and nano-crystal, and blue emission in the film. We attributed interstitial zinc and interstitial oxygen for the luminescence at blue and green bands. Images acquired by TPL and SHG microscopy are presented, interpretation is provided for granular structure exhibiting strong SHG at granular boundaries.