This article focuses on the low-frequency magnetic shielding of double-layer conducting plates with periodic circular apertures. The shielding effectiveness (SE) is measured as the insertion loss of the plates when they are placed between a pair of coaxial loops, one for magnetic field emission and the other for receiving. Our experimental results show that the SE sharply increases with the layer-to-layer spacing increasing from zero to the aperture diameter. For aluminum plates with 1 mm thickness, 20 mm unit cell, and 10 mm aperture diameter, the enhancement is approximately 10 dB and 20 dB for 3 mm and 9 mm spacing, respectively. In addition, the effect of the lateral deviation on the SE is evident only if the spacing is smaller than the aperture diameter.

This paper presents calculations of Raman enhancement for stratified concentric silicon-silver nanocylinders. The Raman enhancement factors of double-layer and triple-layer structures have been determined. Calculations have been performed for the following two-layer cylinders: Ag/Si(core), hollow silicon tube, and Si/Ag(core), and the following three-layer cylinders: Ag/Si/Ag(core), Si/Ag/Si(core), Si/vacuum/Ag(core), Si/vacuum/Si(core), and Si/Ag/vacuum(core). The results indicate that strong Raman enhancements can be obtained in stratified concentric silicon-silver nanocylinders in suitable conditions. These enhancements are sensitive to the excitation wavelength, the radius of the central material, the layer number, and the thickness of each layer of the stratified concentric silicon-silver nanocylinders. They are mainly attributed to the resonant excitations of the silicon cylinder, the resonant excitations of the silicon shell, the localized surface plasmon resonant excitations of silver, and the mirror effect of silver or silicon. The strongest Raman enhancement is about 1013 in two-layer and 1020 in three-layer concentric silicon-silver nanocylinders. The results indicate that the large Raman enhancement appears when the thin silicon layer is close to the silver.

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.