Intersubband transitions in GaAs coupled-quantum-wells for use as a tunable detector at THz frequencies

We demonstrate a detection mechanism for 2–5 THz radiation using intersubband transitions between anticrossing electron levels in a GaAs/AlGaAs coupled-quantum-well photodiode. The THz radiation is detected as a modulation in the photocurrent generated by a visible laser. This modulation is caused by carrier heating effects due to absorption of energy by intersubband transitions. Since the frequency of the intersubband transitions varies with the electric-field strength, the device can function as a voltage-tunable THz detector.