Bernstein modes in density-modulated two-dimensional electron systems and quantum dots

We have prepared two-dimensional electron systems (2DES) in AlxGa1-xAs/GaAs heterostructures with laterally structured gate electrodes which allow us to tune the system from a density-modulated 2DES into a periodic array of isolated quantum dots. At small modulation amplitudes, with far-infrared transmission spectroscopy in a magnetic field, we observe the expected interaction of the magnetoplasmon with the Bernstein modes at harmonics n omega(c) of the cyclotron frequency omega(c) (n = 2,3 . . .). For large modulation, we find modes which occur below these resonances, e.g., in the regime omega(c) to 2 omega(c).