Enhancement of optical switching parameter and third-order optical   nonlinearities in embedded Si nanocrystals: a theoretical assessment
  Third-order bound-charge electronic nonlinearities of Si nanocrystals (NCs) embedded in a wide band-gap matrix representing silica are theoretically studied using an atomistic pseudopotential approach. Nonlinear refractive index, two-photon absorption and optical switching parameter are examined from small clusters to NCs up to a size of 3 nm. Compared to bulk values, Si NCs show higher third-order optical nonlinearities and much wider two-photon absorption threshold which gives rise to enhancement in the optical switching parameter. 
Hasan Y{\i}ld{\i}r{\i}m, Ceyhun Bulutay