Raman enhancement in a couple of nanocylinders (one made of silicon and one made of silver) has been calculated in our work. A formulation for enhanced Raman scattering of semiconductor cylinders is presented. The numerical calculation result based on the formulation indicates that the couple of nanocylinders (one made of silicon and one made of silver) can enhance the electric field in the silicon cylinder greatly and shows strong enhancement for volume average compared with bulk silicon. The largest enhancements per unit volume approach 107 times as compared with bulk crystalline silicon. The silicon and silver nanocylinder structures can combine useful features of the resonant excitations of silicon cylinder and the effect of resonant interaction between silicon cylinder and silver cylinder. This leads to the giant enhancement in the field inside the silicon cylinder and hence an increased Raman scattering. Moreover the results indicate that the interaction between the silicon cylinder and the silver cylinder is very strong under proper conditions.

The light localization effects in silicon photonic crystal cavities at different disorder degrees have been studied using the finite difference time domain (FDTD) method in this paper. Numerical results showed that localization occurs and enhancement can be gained in the region of the cavity under certain conditions. The stabilities of the localization effects due to the structural perturbations have been investigated too. Detailed studies showed that when the degree of structural disorder is small(about 10%), the localization effects are stable, the maximum enhancement factor can reach 16.5 for incident wavelength of 785 nm and 23 for 850 nm in the cavity, with the degree of disorder about 8%. The equivalent diameter of the localized spot is almost constant at different disorder degrees, approximating to ${\lambda \mathord{/ {\vphantom {\lambda 7}} \kern-\nulldelimiterspace} 7}$λ/7, which turned out to be independent on the structural perturbation.