Far-infrared induced current in a ballistic channel-potential barrier structure

We consider electron transport in a ballistic multimode channel structure i n the presence of a transversely polarized far-infrared (FIR) field. The ch annel structure consists of a long resonance region connected to an adiabat ic widening with a potential barrier at the end. At frequencies that match the mode energy separation in the resonance region we find distinct peaks i n the photocurrent, caused by Rabi oscillations in the mode population. For an experimental situation in which the width of the channel is tunable via gates, we propose a method for reconstructing the spectrum of propagating modes, without having to use a tunable FIR source. With this method the cha nge in the spectrum as the gate voltage is varied can be monitored. [S0163- 1829(99)01447-2].