Plasmon-enhanced second harmonic generation in the laser-irradiated   cubic metal nanoparticles
  The plasmon-enhanced second harmonic generation in the subwavelength neutral metal cubic nanoparticles is calculated for the first time in the hydrodynamic and cold plasma approximations. The theory is developed that takes into account all singularities of the electromagnetic field at the cubic nanoparticle surface. The results are compared to the linear case for the nanocube and to those for a spherical nanoparticle. In the latter case, they demonstrate very strong enhancement of the local field strength and the second harmonic signal. 
S. V. Fomichev and A. M. Bratkovsky
cond-mat.mes-hall