Very low saturation intensity and ultrafast response of 1.5 /spl mu/m intersubband absorption in n-doped InGaAs/AlAsSb MQW

It is theoretically shown that an extremely low saturation intensity (<0.05 mW//spl mu/m/sup 2/) as well as an ultrafast (/spl sim/1.3 ps) response are possible in 1.5 /spl mu/m intersubband absorption in n-doped InGaAs/AlAsSb multiple quantum wells with electron concentration of /spl sim/1/spl times/10/sup 19/ cm/sup -3/. Such a low saturation intensity is ascribed to the /spl delta/-function-like absorption spectra of the intersubband transition and a reduced dephasing rate achieved by high doping.