Linear and nonlinear intersubband optical absorption in a strained double barrier quantum well

A systematic theoretical investigation of intersubband optical absorption in AlGaAs/AlAs/InGaAs strained double barrier quantum well (SDBQW) structure is presented for the first time. Electron states in a SDBQW are found to be adequately described within the framework of the envelope function approach which includes the effects of subband nonparabolicity and strain. The linear and the third-order nonlinear intersubband optical absorption are calculated using the density matrix formalism in which intrasubband relaxation is taken into account. Subband nonparabolicity and elastic strain are found to significantly influence both electron states and intersubband optical absorption. In the case of small well width, the inner-barrier thickness affects both electron states and optical absorption. Our results can be used in design of high performance quantum well infrared photodetectors operating in the important wavelength region between 3 and 5 μm.