Theory of second-harmonic generation in colloidal crystals
  On the basis of the Edward-Kornfeld formulation, we study the effective susceptibility of secondharmonic generation (SHG) in colloidal crystals, which are made of graded metallodielectric nanoparticles with an intrinsic SHG susceptibility suspended in a host liquid. We find a large enhancement and redshift of SHG responses, which arises from the periodic structure, local field effects and gradation in the metallic cores. The optimization of the Ewald-Kornfeld formulation is also investigated. 
J. P. Huang, Y. C. Jian, and C. Z. Fan (Department of Physics, Fudan   University, Shanghai), K. W. Yu (Department of Physic...