We present a theoretical study of long-range surface plasmons propagating in a thin metallic film clad between two identical uniaxial anisotropic dielectric crystals. We show that the proper orientation of the optical axis of the crystal with respect to the metal surface enhances the propagation length of surface plasmons. Since the proper orientation depends on surface plasmon frequency, we give the results for the propagation length in a wide range of frequencies, including the telecommunication region. To increase the role of anisotropy, we consider artificial substrates from photonic crystals, which possess an order of magnitude stronger anisotropy than the natural optical crystals. We propose Kronig-Penney model for plasmonic crystal where the substrate is a periodic sequence of dielectric delta peaks. In this model the dispersion relation for surface plasmon has a band structure where the band width tends to zero when the frequency approaches the resonant frequency.
Optical shrink for process migration, manufacturing process variation, temperature and voltage changes lead to clock skew as well as path delay variations in a manufactured chip. Such variations end up degrading the performance of manufactured chips. Since, such variations are hard to predict in pre-silicon phase, tunable clock buffers have been used in several designs. These buffers are tuned to improve maximum operating clock frequency of a design. Previously, we have presented an algorithmic approach that uses delay measurements on a few selected patterns to determine which buffers should be targeted for tuning. In this paper, a study on impact of tunable buffer placement on performance is reported. Greatest benefit from tunable buffer placement is observed, when the clock tree is designed by the proposed tuning system assuming random delay perturbations during design. Accordingly, we present a clock tree synthesis procedure which offer very good protection against process variation as borne out by the results.
Coupling of Rayleigh waves propagating along two metal surfaces separated by a narrow fluid channel is predicted and experimentally observed. Although the coupling through a fluid (water) is weak, a strong synchronization in propagation of Rayleigh waves even for the metals with sufficiently high elastic contrast (brass and aluminum) is observed. Dispersion equation for two polarizations of the coupled Rayleigh waves is derived and experimentally confirmed. Excitation of coupled Rayleigh waves in a channel of finite length leads to anomalously low transmission of acoustic energy at discrete set of resonant frequencies. This effect may find useful applications in the design of acoustic metamaterial screens and reflectors.
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