Saturation of large nonresonant third and fifth order optical nonlinearities from ZnSe quantum dots in glass-matrix thin films

Abstract

Large nonresonant optical Kerr coefficient without apparent nonlinear absorption was obtained from ZnSe-doped glass thin films grown by pulsed laser deposition. A third nonlinear refractive index of +0.87 to 1.56 cm(2)/GW and fifth order of + 17.2 cm(4)/GW(2) were measured for a light beam having femtosecond pulsewidth with photon energy below one half bandgap using the Z-scan method. Besides the enhancement of the nonlinear refractive index results from the two-photon near resonance and quantum confinement effect, the intensity-induced saturation of nonlinear refractive index is explained by the quadratic optical Stark shift.