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Surface plasmon coupling efficiency from nanoslit apertures to metal-insulator-metal waveguides Appl. Phys. Lett. 101, 121112 (2012) Polarizability of supported metal nanoparticles: Mehler-Fock approach J. Appl. Phys. 112, 064312 (2012) On the mechanism of electrochemical modulation of plasmonic resonances Appl. Phys. Lett. 101, 121109 (2012) Resonance plasmon linewidth oscillations in spheroidal metallic nanoparticle embedded in a dielectric matrix J. Appl. Phys. 112, 064306 (2012) Influence of surface plasmon propagation on leakage radiation microscopy imagingWe report far infrared (FIR) studies of plasmons in spatially modulated two-dimensional electron gases (2DEGs) in AlGaPLs/GaAs heterostructures using biased overlaid metal gratings, including itzterdigituted gratings, both as optical couplers and as spatially modulating gates. Comparison of the experimental results with the predictions of scattering matrix calculations of the FIR response of a modulated 2DEG in the presence of a perfectly conducting lame&r grat.ing allow us to deduce the spatial variation of the number density distribution in the 2DEG as a function of grating bias. For the interdigitated grating gates, the 2DEG can be modulated at a period of twice that of the grating fingers by differentially biasing alternate fingers; 2D plasmon resommces have been observed at half-integral values of the grating wave vector G, corresponding to the electrically induced periodicity of the 2DEG modulation itself acting as an optical coupler in addition to the metal grating. The observed G/2 plasmon frequencies decrease with increasing amplitude of the 2DEG number density modulation, in quantitative agreement with those obtained from scattering matrix calculations of the optical response of a modulated 2DEG under a perfectly conducting lamellar grating; calculations of the oscillating charge density profiles show that this occurs because, as the modulation amplitude inc.reases, the oscillation becomes localized in regions of low 2DEG number density which are also under one of the sets of grating fingers, and is therefore better screened.

The far-infrared optical response of a structure consisting of a perfectly conducting grating gate on a modulation-doped GaAs/AlGaAs heterojunction has been calculated using the scattering matrix technique. The grating gate allows coupling between the incident radiation and the plasmon resonance of the two-dimensional electron gas (2DEG) in such a system, but also modifies the dispersion relation for the plasmon because of screening by the image charge distribution induced on the grating gate. Using the scattering matrix technique allows this screening effect to be modeled more accurately than has hitherto been possible, and our calculations show that the induced charge is concentrated at the edges of the grating fingers. The sinusoidal profile of the oscillating charge density in the 2DEG distorts so that the maximum amplitude of the oscillation is close to these edges, and the plasmon frequency is determined by the amount of distortion of the plasmon charge density profile and the additional screening gained through the distortion. Plasmon frequencies are calculated for a wide range of lamellar grating mark/space ratios, and are found to lie between the extremes predicted for plasmons in 2DEGs close to a vacuum interface and close to a continuous metal gate.

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