Abstract

We report far-infrared measurements of the shift of the plasmon resonance of a 2DEG drifting under a metal grating coupler of symmetric profile. Measurements were made as a function of lateral current through the GaAs AlGaAs heterostructure 2DEG in samples with different grating periods. Reference spectra were taken in a strong magnetic field which sweeps the (magneto-)plasmon resonance to higher energy. The plasmon energy is observed to be shifted downwards with increasing drift velocity, but this behaviour is non-linear. The results compare well with computations of the optical response of a drifting 2DEG near a metal grating performed using the Scattering Matrix method. The discrepancy can be accounted for by a slight decrease in the number density of carriers at high currents. The expected splitting of the plasmon caused by the presence of the grating is not observed at low drift velocity because the higher frequency mode is antisymmetric and is not coupled to radiation by a symmetric grating profile.

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