Room-temperature GaAs/AlGaAs multiple-quantum-well optical modulators for the 3-5 µm atmospheric window

We have investigated electrically modulated optical filters based on intersubband transitions in GaAs/AlGaAs quantum wells. By using narrow quantum wells with high Al concentration - up to 100% - in the barriers, filters absorbing selectively down to the atmospheric window 3-5 µm were achieved. An efficient modulation of the intersubband absorption was obtained at room temperature and under low-bias conditions, less than 5 V. Applications of the filters for multiple gas detection (multicolour detection) are discussed.