Bernstein modes in grating-coupled 2DEGs

Abstract

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.

Comparative study on calculated terahertz absorption spectra of different heterostructure materials with external magnetic field

“…While at cryogenic temperature, the cyclotron resonance and its high order harmonics were distinguishable from the MPP resonances. It should be mentioned that at specific magnetic field and plasmon wavevector, the MPP modes will probably couple with Bernstein modes and the frequency splitting behavior will appear particularly at cryogenic temperature [14,16]. Similar theoretical and experimental results for the AlGaN/GaN [24,25] and CdMgTe/CdTe [15,19] heterostructure materials have been reported.…”

“…Depending on the sign and amplitude of the bias voltage and the material type, the observed resonant frequency could be altered more or less. The other convenient method to change the resonant frequency was realized by introducing the static magnetic field along the direction perpendicular to the 2DEG plane, where the magnetoplasmon-polaritons (MPPs) modes will dominate in the detector response [14,15]. Both the amplitude and frequency were influenced by the strength of magnetic field.…”

Cyclotron resonance overtones and near-field magnetoabsorption via terahertz Bernstein modes in graphene

“…ics is a weaker effect appearing only due to non-uniform fields. [33][34][35] Our findings reveal the importance of nonlocal light-matter interaction in subwavelength THz devices.…”

Magnetoplasmons in a High Electron Mobility GaAs/AlGaAs Heterostructure

“…The observation of the second harmonic of the CR might be a result of the Bernstein modes in the sample [9]. The high number of observed modes of magnetoplasmons can be understood as a result of the retardation eects observed in large scale samples [8].…”