Calculations and experimental data are reported on the optical coupling to the Bernstein modes of a two-dimensional electron gas (2DEG) in a perpendicular magnetic field using an overlaid grating coupler. The Bernstein modes are harmonics of the cyclotron resonance and are observed indirectly through their interaction with the 2DEG magnetoplasmon. The optical response of a grating-heterojunction structure is calculated using a modal expansion technique, with the Bernstein modes included semiclassically through non-local corrections to the 2DEG conductivity tensor. Dispersion curves deduced from the calculated spectra show the expected anticrossing behaviour at magnetic fields for which the Bernstein and magnetoplasmon modes have similar frequencies. This calculated dispersion behaviour is in excellent agreement with experimental data on a GaAs/AlGaAs heterojunction sample, underlining the importance of using the full electromagnetic response of the structure, including the periodic screening effects of the coupling grating, in comparisons between theory and experiment. The strength of the coupling to the Bernstein modes is also extremely well modelled.

Direct optical coupling to the plasmon modes of a two-dimensional electron gas in a stratified semiconductor system requires an overlaid grating coupler. Plasmons can be excited with wave vectors equal to integer multiples of the grating wave vector, and the periodic screening by the grating splits these into two modes, symmetric and antisymmetric with respect to the grating profile. We present calculations of the dispersions and optical coupling strengths for several orders of both modes in a typical structure, and show that the splitting and coupling strengths of the higher order modes oscillate with varying grating mark fraction. These effects are discussed in terms of the oscillating field strengths and charge density profiles.

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We report an inelastic light-scattering study of the intrasubband plasmons of a single two-dimensional electron gas (2DEG) at a GaAs/Al"Gal "As heterointerface under a grating Schottky gate with a period comparable to the plasmon wavelength. Gaps appear in the plasmon dispersion relation because of the spatially periodic screening by the gate, and these are successfully modeled using a scattering matrix calculation of the electromagnetic response of the system. Biasing the gate periodically modulates the 2DEG carrier density, and has a striking e6ect on the plasmon dispersion relation that cannot be fully explained within the existing theoretical framework.

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