Strong coupling between localized particle plasmons and optical waveguide modes leads to drastic modifications of the transmission of metallic nanowire arrays on dielectric waveguide substrates. The coupling results in the formation of a new quasiparticle, a waveguide-plasmon polariton, with a surprisingly large Rabi splitting of 250 meV. Our experimental results agree well with scattering-matrix calculations and a polariton-type model. The effect provides an efficient tool for photonic band gap engineering in metallodielectric photonic crystal slabs. We show evidence of a full one-dimensional photonic band gap in resonant plasmon-waveguide structures.

We propose a generally applicable velocity matching method for THz-pulse generation by optical rectification in the range below the phonon frequency of the nonlinear material. Velocity matching is based on pulse front tilting of the ultrashort excitation pulse and is able to produce a large area THz beam. Tuning of the THz radiation by changing the tilt angle is experimentally demonstrated for a narrow line in the range between 0.8- 0.97 times the phonon frequency. According to model calculations broadband THz radiation can be generated at lower frequencies. Advantages of the new velocity matching technique in comparison to the electro-optic Cherenkov effect and non-collinear beam mixing are discussed.

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We numerically study the spectral response of 'U'-shaped split-ring-resonators at normal incidence with respect to the resonator plane. Based on the evaluation of the near-field patterns of the resonances and their geometry-dependent spectral positions, we obtain a comprehensive and consistent picture of their origin. We conclude that all resonances can be understood as plasmonic resonances of increasing order of the entire structure. In particular, for an electrical field polarized parallel to the gap the so-called LC-resonance corresponds to the fundamental plasmonic mode and, contrary to earlier interpretations, the electrical resonance is a second order plasmon mode of the entire structure. The presence of further higher order modes is discussed.

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The interaction of visible light with the particle-plasmon resonance of metallic nanoparticles can be controlled by geometrical arrangement of nanoparticle arrays. These arrays are placed on a substrate that supports guided modes in the wavelength range of the particle plasmon. Coupling of this particle-plasmon resonance to the directly incident light and to the waveguide modes results in almost complete suppression of light extinction within narrow spectral bands due to destructive interference. Variation of the structure parameters allows continuous tuning of these high-transmission bands across the particle-plasmon resonance.

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