Oscillations in the frequencies and coupling strengths of two-dimensional plasmons induced by grating couplers

Abstract

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.

Plasmon enhanced electron drag and terahertz photoconductance in a grating-gated field-effect transistor with two-dimensional electron channel

“…The latter approximation is justified when l w l << − and l d << . For narrow grating slits the splitting of the − ω -and + ω -modes decreases [12,13], and both plasmon resonances merge producing one combined resonance of complex shape shown in Fig. 3.…”

“…2, Fourier amplitudes of the total in-plane electric field Coupling of an external THz field to the plasmons becomes stronger for the grating gates with narrow slits between the fingers [11][12][13]. Stronger coupling results in the increased height of the photoresponse peaks.…”

“…In our calculations we used the following parameters for the grating-gated GaAs/AlGaAs FET: ) in-plane electric field distribution under the grating gate finger, respectively [12,13]. Because of the symmetry, only an even mode is optically active and can be excited by an external EM field.…”

Transmission line theory of collective plasma excitations in periodic two-dimensional electron systems: Finite plasmonic crystals and Tamm states

“…The plasmon energy band spectrum has been found numerically in various approximations [32][33][34][35][36]. Density and field distributions in the split plasmon modes at the edges of the band gap and their interaction with incident EM field have also been analyzed [37][38][39]. Recently plasmonic band spectrum has been calculated in the gated 2DEG with periodically modulated plasma wave velocity [40].…”

Plasmon Enhanced Electron Drag and Terahertz Photoconductance in a Grating-Gated Field-Effect Transistor with Two-Dimensional Electron Channel

“…The main resonant peak in Fig. 1 corresponds to the Coupling of an external THz field to the plasmons becomes stronger for the grating gates with narrow slits between the fingers [11][12][13]. Stronger coupling results in the increased height of the photoresponse peaks.…”