Size dependence of nonlinear optical absorption and refraction of Mn-doped ZnSe nanocrystals

Nonlinear refractive index and nonlinear absorption coefficient of high-quality Mn:ZnSe nanocrystals are measured by z-scan technique at 800nm wavelength. The synthesized nanocrystals with nucleation doping have tunable wavelength (between 565–610nm), high quantum yield (∼50%), and high thermal as well as photochemical stabilities. The unique nanocrystal structure (with a MnSe core, Zn1−xMnxSe diffusion region, and an outer ZnSe layer) shows size-dependent nonlinear effects, which can be qualitatively explained by a simple model using crystal field. Studies of nonlinear optical properties are very important and necessary for high-power optical applications (such as light-emitting diodes and lasers) of such Mn-doped ZnSe nanocrystals.