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

We have investigated electrically modulated optical filters based on inters ubband transitions in GaAs/AlGaAs quantum wells. By using narrow quantum we lls with high Al concentration-up to 100%-in the barriers, filters absorbin g selectively down to the atmospheric window 3-5 mu m were achieved. An eff icient modulation of the intersubband absorption was obtained at room tempe rature and under low-bias conditions, less than 5 V. Applications of the fi lters for multiple gas detection (multicolour detection) are discussed.