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 intersubba nd transitions between anticrossing electron levels in a GaAs/AlGaAs couple d-quantum-well photodiode. The THz radiation is detected as a modulation in the photocurrent generated by a visible laser. This modulation is caused b y carrier heating effects due to absorption of energy by intersubband trans itions. Since the frequency of the intersubband transitions varies with the electric-field strength, the device can function as a voltage-tunable THz detector. (C) 2000 American Institute of Physics. [S0003-6951(00)02012-X].