OSCILLATIONS IN THE FREQUENCIES AND COUPLING STRENGTHS OF 2-DIMENSIONAL PLASMONS INDUCED BY GRATING COUPLERS

Direct optical coupling to the plasmon modes of a two-dimensional elec tron gas in a stratified semiconductor system requires an overlaid gra ting coupler Plasmons can be excited with wave vectors equal to intege r multiples of the grating wave vector, and the periodic screening by the grating splits these into two modes, symmetric and antisymmetric w ith respect to the grating profile. We present calculations of the dis persions and optical coupling strengths for several orders of both mod es in a typical structure, and show that the splitting and coupling st rengths of the higher order modes oscillate with varying grating mark fraction. These effects are discussed in terms of the oscillating fiel d strengths and charge density profiles.