ABSTRACT
We observe deterministic chaos in a simple network of electronic logic gates that are not regulated by a clocking signal. The resulting power spectrum is ultrawide band, extending from dc to beyond 2 GHz. The observed behavior is reproduced qualitatively using an autonomously updating Boolean model with signal propagation times that depend on the recent history of the gates and filtering of pulses of short duration, whose presence is confirmed experimentally. Electronic Boolean chaos may find application as an ultrawide-band source of radio waves.
Subject(s)
Logistic Models , Nonlinear Dynamics , Signal Processing, Computer-Assisted , Computer SimulationABSTRACT
Plasmon-enhanced transmission of light incident on a periodic array of nanoscale, asymmetric cruciform patterns is demonstrated. The corresponding transmission spectra are shown to be polarization dependent and possess unique properties, such as the existence of isosbestic points for which the transmission is polarization insensitive. Transmission peaks corresponding to localized surface plasmon resonances and extended surface plasmons are also identified.
ABSTRACT
Optical-field enhancement and confinement for an asymmetrically illuminated nanoscopic Au tip suspended over a planar Au substrate is investigated both numerically and experimentally. The spatial field distribution of the tip-sample system was calculated using the full 3D finite-difference time-domain method. The calculation enables investigation of the effects of the substrate-tip placement, angle of incidence, and spectral response. The tip plasmon response leads to a significant (up to ~70 times) local field enhancement between the tip and substrate. The enhancement is found to be extremely sensitive to the tip-sample separation distance. Tip-enhanced Raman scattering experiments were performed and the numerical results provide a consistent description of the observed field localization and enhancement.
