Nonlinear optical properties of ultra-fine nanocrystalline sno synthesised through microwave-assisted hydrothermal route

The purpose of this Letter is to prepare and investigate the nonlinear optical properties of nanocryatalline SnO. Using a microwave-assisted hydrothermal method, nanoparticles of SnO have been synthesised. It was noticed that, at 600 W microwave power, the pure tetragonal single phase of SnO existed and at higher-power SnO₂ starts appearing. The grain size of SnO was ~3 nm and UV-vis measurements showed the existence of an excitonic peak at ~270 nm. The appearance of this excitonic peak for nanocrystallites SnO may be attributed to the conversion of bandgap from indirect in bulk SnO to direct bandgap in nanocrystallites. The third-order nonlinear optical properties of SnO nanoparticles were also studied using a continuous-wave He-Ne laser by z-scan technique. The nonlinear refractive indices of SnO nanoparticles were obtained from close aperture in order of 10^-7 cm²/W with negative sign and the nonlinear absorption indices of these nanoparticles were obtained from open aperture with negative sign.