Enhancement of third-order nonlinearity of nanocrystalline GaSb embedded in silica film

Nanocrystalline GaSb embedded in SiO2 film was grown by radio frequency co-sputtering. The nonlinear optical properties of the GaSb–SiO2 composite film have been studied at 632.8 nm by use of Z-scan technology. The appearance of a two photon absorption is predicted energetically above the exciton resonance for quantum-dot radii, which are between the electron and hole radii. The nonlinear refractive index of the GaSb–SiO2 composite film is positive. It shows that the GaSb–SiO2 composite film posses a large third-order nonlinear susceptibility about 7.84×10−9 esu. Room temperature transmission spectrum shows that the absorption edge exhibits a very large blue shift of 2.7 eV compared with that of bulk GaSb, which is mainly explained by the quantum confinement effect.