Optically poled SHG and THG effects in cesium doped zinc oxide nanorods

The hexagonal wurtzite structure of the synthesized undoped and cesium (Cs) doped zinc oxide (ZnO) nanorods were confirmed with X-ray diffraction patterns. Further analysis with field emission scanning electron microscope images and energy dispersive X-ray spectra revealed the c-axis oriented hexagonal morphology of the samples with chemical composition. Optical poling through 337 nm nitrogen laser has been adopted to enhance the nonlinear optical properties. When the power density of the fundamental laser beam from Nd:YAG laser of 1064 nm matched with the band edge of the samples, resonant absorption takes place leading to the enhanced NLO properties. The interstitial occupancy of the dopants in 3 and 5 mol% CsZnO increases the band tailing in the forbidden energy gap. The minimum of Urbach energy calculated from UV–Vis absorption spectra corresponding to 1 mol% CsZnO revealed more ordering in the sample. More enhanced second and third order NLO effects were observed in this sample having larger crystallite size, lesser diameter, lesser band gap, minimum urbach energy and higher electron–phonon interaction.